Neutrophil serine proteases: specific regulators of inflammation

Cathepsin G promotes arteriovenous fistula maturation by positively regulating the MMP2/MMP9 pathway

BACKGROUND

Arteriovenous fistula (AVF) is currently the preferred vascular access for hemodialysis patients. However, the low maturation rate of AVF severely affects its use in patients. A more comprehensive understanding and study of the mechanisms of AVF maturation is urgently needed.

METHODS AND RESULTS

In this study, we downloaded the publicly available datasets (GSE119296 and GSE220796) from the Gene Expression Omnibus (GEO) and merged them for subsequent analysis. We screened 84 differentially expressed genes (DEGs) and performed the functional enrichment analysis. Next, we integrated the results obtained from the degree algorithm provided by the Cytohubba plug-in, Molecular complex detection (MCODE) plug-in, weighted gene correlation network analysis (WGCNA), and Least absolute shrinkage and selection operator (LASSO) logistic regression. This integration allowed us to identify CTSG as a hub gene associated with AVF maturation. Through the literature search and Pearson's correlation analysis, the genes matrix metalloproteinase 2 (MMP2) and MMP9 were identified as potential downstream effectors of CTSG. We then collected three immature clinical AVF vein samples and three mature samples and validated the expression of CTSG using immunohistochemistry (IHC) and double-immunofluorescence staining. The IHC results demonstrated a significant decrease in CTSG expression levels in the immature AVF vein samples compared to the mature samples. The results of double-immunofluorescence staining revealed that CTSG was expressed in both the intima and media of AVF veins. Moreover, the expression of CTSG in vascular smooth muscle cells (VSMCs) was significantly higher in the mature samples compared to the immature samples. The results of Masson's trichrome and collagen I IHC staining demonstrated a higher extent of collagen deposition in the media of immature AVF veins compared to the mature. By constructing an in vitro CTSG overexpression model in VSMCs, we found that CTSG upregulated the expression of MMP2 and MMP9 while downregulating the expression of collagen I and collagen III. Furthermore, CTSG was found to inhibit VSMC migration.

CONCLUSIONS

CTSG may promote AVF maturation by stimulating the secretion of MMP2 and MMP9 from VSMCs and reducing the extent of medial fibrosis in AVF veins by inhibiting the secretion of collagen I and collagen III.

Identification of potential biomarkers for sepsis based on neutrophil extracellular trap-related genes

Sepsis is a highly lethal disease that poses a serious threat to human health. Increasing evidence indicates that neutrophil extracellular traps (NETs) are key factors in the pathological progression of sepsis. This study aims to screen potential biomarkers for sepsis and delve into their regulatory function in the pathogenesis. We downloaded 6 microarray datasets from the Gene Expression Omnibus (GEO) database, with 4 as the training sets and 2 as the validation sets. NETs-related genes (NRGs) were obtained from relevant literature. Differential expression analysis was performed on four training sets separately. We intersected differentially expressed genes (DEGs) from the four training sets and NRGs, finally resulting in 19 NETs-related sepsis genes. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) unearthed that NETs-related sepsis genes were majorly abundant in functions and pathways such as defense response to bacterium and Neutrophil extracellular trap formation. Using the PPI network, the MCC algorithm, and the MCODE algorithm in the CytoHubba plugin, 7 sepsis hub genes (ELANE, TLR4, MPO, PADI4, CTSG, MMP9, S100A12) were identified. ROC curve for each Hub gene in the training and validation sets were plotted, which revealed that the Area Under Curve (AUC) values are all greater than 0.6, indicating good classification ability. A total of 349 miRNAs targeting Hub genes were predicted in the mirDIP database, and 620 lncRNAs targeting miRNAs were predicted in the ENCORI database. The ceRNA regulatory network was constructed using Cytoscape software. Finally, we employed the cMAP database to predict small molecular complexes as potentially effective drugs for the treatment of sepsis, such as chloroquine, harpagoside, and PD-123319. In conclusion, this project successfully identified 7 core genes, which may serve as promising candidates for novel sepsis biomarkers. Meanwhile, we constructed a related ceRNA network and predicted potential targeted drugs, providing potential therapeutic targets and treatment strategies for sepsis patients.

Neutrophil and neutrophil extracellular trap involvement in neutrophilic asthma: A review

Asthma is a highly prevalent chronic inflammatory disease characterized by variable airflow obstruction and airway hyperresponsiveness. Neutrophilic asthma (NA) is classified as "type 2 low" asthma, defined as 65% or more neutrophils in the total cell count. There is no clear consensus on the pathogenesis of NA, and the accumulation of neutrophils and release of neutrophil extracellular traps (NETs) may be responsible for its development. A NET is a large extracellular meshwork comprising cell membrane and granule proteins. It is a powerful antimicrobial defence system that traps, neutralizes, and kills bacteria, fungi, viruses, and parasites and prevents the spread of microorganisms. However, dysregulation of NETs may lead to chronic airway inflammation, is associated with worsening of asthma, and has been the subject of major research advances in chronic lung diseases in recent years. NA is insensitive to steroids, and there is a need to find effective biomarkers as targets for the treatment of NA to replace steroids. This review analyses the mechanisms of action between asthmatic neutrophil recruitment and NET formation and their impact on NA development. It also discusses their possible therapeutic significance in NA, summarizing the advances made in NA agents and providing strategies for the treatment of NA, provide a theoretical basis for the development of new therapeutic drugs, thereby improving the level of diagnosis and treatment, and promoting the research progress in the field of asthma.

Cathepsin C in health and disease: from structural insights to therapeutic prospects

Cathepsin C (CTSC) is a lysosomal cysteine protease constitutively expressed at high levels in the lung, kidney, liver, and spleen. It plays a key role in the activation of serine proteases in cytotoxic T cells, natural killer cells (granzymes A and B), mast cells (chymase and tryptase) and neutrophils (cathepsin G, neutrophil elastase, proteinase 3) underscoring its pivotal significance in immune and inflammatory defenses. Here, we comprehensively review the structural attributes, synthesis, and function of CTSC, with a focus on its variants implicated in the etiopathology of several syndromes associated with neutrophil serine proteases, including Papillon-Lefevre syndrome (PLS), Haim-Munk Syndrome (HMS), and aggressive periodontitis (AP). These syndromes are characterized by palmoplantar hyperkeratosis, and early-onset periodontitis (severe gum disease) resulting in premature tooth loss. Due to the critical role played by CTSC in these and several other conditions it is being explored as a potential therapeutic target for autoimmune and inflammatory disorders. The review also discusses in depth the gene variants of CTSC, and in particular their postulated association with chronic obstructive pulmonary disease (COPD), COVID-19, various cancers, anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis, sudden cardiac death (SCD), atherosclerotic vascular disease, and neuroinflammatory disease. Finally, the therapeutic potential of CTSC across a range of human diseases is discussed.

The serine protease inhibitor HAMpin-1 produced by the ectoparasite Hyalomma anatolicum salivary gland modulates the host complement system

Ticks are notable vectors of diseases affecting both humans and animals, with Hyalomma anatolicum being of particular significance due to its wide distribution and capability to transmit a variety of pathogens, including Theileria annulata, and Crimean-Congo haemorrhagic fever (CCHF) virus. This study aimed to investigate the inhibitory effects of Hyalomma anatolicum salivary gland extract (HaSGE) and the identification of its key component on the complement system of the host's innate immune defense. We demonstrated that HaSGE exerts a dose-dependent inhibition on the complement activation in a host-specific manner. Mechanistic studies revealed that HaSGE interferes with blocking the deposition and cleavage of complement proteins C3 and C5, thus preventing the formation of the membrane attack complex (MAC). Further, we identified a serine protease inhibitor, HAMpin-1, from the HaSGE through proteomic analysis and characterized its structure, function, and interaction with complement proteins. HAMpin-1 exhibited potent inhibitory activity against chymotrypsin and cathepsin-G, and notably, it is the first serpin from ticks shown to inhibit the classical and lectin pathways of the complement system. The expression of HAMpin-1 was highest in the salivary glands, suggesting its crucial role in blood feeding and immune evasion. Our findings revealed one of the potential mechanisms employed by H. anatolicum to modulate host immune responses at the interface, offering new insights into tick-host interactions.

Role of Neutrophils in the Development of Steatotic Liver Disease

This review explores the biological aspects of neutrophils, their contributions to the development of steatotic liver disease, and their potential as therapeutic targets for the disease. Although alcohol-associated and metabolic dysfunction-associated liver diseases originate from distinct etiological factors, the two diseases frequently share excessive lipid accumulation as a common contributor to their pathogenesis, thereby classifying them as types of steatotic liver disease. Dysregulated lipid deposition in the liver induces hepatic injury, triggering the activation of the innate immunity, partially through neutrophil recruitment. Traditionally recognized for their role in microbial clearance, neutrophils have recently garnered attention for their involvement in sterile inflammation, a pivotal component of steatotic liver disease pathogenesis. In conclusion, technological innovations, including single-cell RNA sequencing, have gradually disclosed the existence of various neutrophil subsets; however, how the distinct subsets of neutrophil population contribute differentially to the development of steatotic liver disease remains unclear.

Cathepsin C from extracellular histone-induced M1 alveolar macrophages promotes NETosis during lung ischemia-reperfusion injury

Primary graft dysfunction (PGD) is a severe form of acute lung injury resulting from lung ischemia/reperfusion injury (I/R) in lung transplantation (LTx), associated with elevated post-transplant morbidity and mortality rates. Neutrophils infiltrating during reperfusion are identified as pivotal contributors to lung I/R injury by releasing excessive neutrophil extracellular traps (NETs) via NETosis. While alveolar macrophages (AMs) are involved in regulating neutrophil chemotaxis and infiltration, their role in NETosis during lung I/R remains inadequately elucidated. Extracellular histones constitute the main structure of NETs and can activate AMs. In this study, we confirmed the significant involvement of extracellular histone-induced M1 phenotype of AMs (M1-AMs) in driving NETosis during lung I/R. Using secretome analysis, public protein databases, and transwell co-culture models of AMs and neutrophils, we identified Cathepsin C (CTSC) derived from AMs as a major mediator in NETosis. Further elucidating the molecular mechanisms, we found that CTSC induced NETosis through a pathway dependent on NADPH oxidase-mediated production of reactive oxygen species (ROS). CTSC could significantly activate p38 MAPK, resulting in the phosphorylation of the NADPH oxidase subunit p47phox, thereby facilitating the trafficking of cytoplasmic subunits to the cell membrane and activating NADPH oxidase. Moreover, CTSC up-regulated and activated its substrate membrane proteinase 3 (mPR3), resulting in an increased release of NETosis-related inflammatory factors. Inhibiting CTSC revealed great potential in mitigating NETosis-related injury during lung I/R. These findings suggests that CTSC from AMs may be a crucial factor in mediating NETosis during lung I/R, and targeting CTSC inhition may represent a novel intervention for PGD in LTx.

Chinese Medicine Linggui Zhugan Formula Protects against Diabetic Kidney Disease in Close Association with Inhibition of Proteinase 3-mediated Podocyte Apoptosis in Mice

ETHNOPHARMACOLOGICAL RELEVANCE

Linggui-Zhugan (LGZG) comprises four herbs and is a classic formula in traditional Chinese medicine. There is strong clinical evidence of its pleiotropic effects in the prevention of diabetes and its related complications. Although several classes of drugs are currently available for clinical management of diabetic kidney disease (DKD), tight glycemic and/or hypertension control may not prevent disease progression. This study evaluated the therapeutic effect of the ethnopharmacological agent LGZG on DKD.

AIM OF THE STUDY

This study aimed to investigate the effects of LGZG formula with standard quality control on experimental DKD and its related metabolic disorders in animal model. Meanwhile, the present study aimed to investigate regulatory effects of LGZG on renal proteinase 3 (PR3) to reveal mechanisms underlying renoprotection benefits of LGZG.

MATERIALS AND METHODS

LGZG decoction was fingerprinted by high-performance liquid chromatography for quality control. An experimental model of DKD was induced in C57 BL/6J mice by a combination of high-fat diet feeding, uninephrectomy, and intraperitoneal injection of streptozocin. The LGZG decoction was administrated by daily oral gavage.

RESULTS

Treatment with LGZG formula significantly attenuated DKD-like traits (including severe albuminuria, mesangial matrix expansion, and podocyte loss) and metabolic dysfunction (disordered body composition and dyslipidemia) in mice. RNA sequencing data revealed a close association of LGZG treatment with marked modulation of signaling pathways related to podocyte injury and cell apoptosis. Mechanistically, LGZG suppressed the DKD-triggered increase in renal PR3 and podocyte apoptosis. In-vitro incubation of mouse immortalized podocytes with LGZG-medicated serum attenuated PR3-mediated apoptosis.

CONCLUSION

Our data demonstrated that the LGZG formula protected against DKD in mice and was closely associated with its inhibitory effects on PR3-mediated podocyte apoptosis.

Curcumin attenuates lupus nephritis by inhibiting neutrophil migration via PI3K/AKT/NF-κB signalling pathway

OBJECTIVE

To investigate the role of curcumin in the treatment of lupus nephritis (LN) by inhibiting the migration of neutrophils and the underlying mechanism involved.

METHODS

Two lupus mouse models, MRL/lpr mice and R848-treated mice, were treated with 50 mg/kg curcumin by intraperitoneal injection. H&E and Masson staining were used to estimate histopathological changes in the kidney. Immunofluorescence was used to assess the deposition of immune complexes. The expression of inflammatory factors was detected by enzyme-linked immunosorbent assay (ELISA) and real-time reverse transcription polymerase reaction (RT-PCR), and the protein expression was detected by western blotting.

RESULTS

We revealed the remarkable potential of curcumin in improving inflammatory conditions in both MRL/lpr mice and R848-induced lupus mice. Curcumin effectively decelerates the progression of inflammation and diminishes the infiltration of neutrophils and their release of pivotal inflammatory factors, thereby reducing inflammation in renal tissues. Mechanistically, curcumin significantly inhibits the expression of p-PI3K, p-AKT and p-NF-κB, which are upregulated by interleukin-8 to induce neutrophil migration and renal inflammation, thereby reducing neutrophil migration and the release of inflammatory factors.

CONCLUSION

Curcumin significantly inhibits the recruitment of neutrophils and the release of proinflammatory factors in the kidney by inhibiting the PI3K/AKT/NF-κB signalling pathway, providing new therapeutic targets and medication strategies for the treatment of LN.

Human Neutrophil Elastase: Characterization of Intra- vs. Extracellular Inhibition

Neutrophil elastase (HNE), like other members of the so-called GASPIDs (Granule-Associated Serine Peptidases of Immune Defense), is activated during protein biosynthesis in myeloid precursors and stored enzymatically active in cytoplasmic granules of resting neutrophils until secreted at sites of host defense and inflammation. Inhibitors thus could bind to the fully formed active site of the protease intracellularly in immature progenitors, in circulating neutrophils, or to HNE secreted into the extracellular space. Here, we have compared the ability of a panel of diverse inhibitors to inhibit HNE in the U937 progenitor cell line, in human blood-derived neutrophils, and in solution. Most synthetic inhibitors and, surprisingly, even a small naturally occurring proteinaceous inhibitor inhibit HNE intracellularly, but the extent and dynamics differ markedly from classical enzyme kinetics describing extracellular inhibition. Intracellular inhibition of HNE potentially affects neutrophil functions and has side effects, but it avoids competition of inhibitors with extracellular substrates that limit its efficacy. As both intra- and extracellular inhibition have advantages and disadvantages, the quantification of intracellular inhibition, in addition to classical enzyme kinetics, will aid the design of novel, clinically applicable HNE inhibitors with targeted sites of action.

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.

Pharmacologic inhibition of dipeptidyl peptidase 1 (cathepsin C) does not block in vitro granzyme-mediated target cell killing by CD8 T or NK cells

Recently developed small-molecule inhibitors of the lysosomal protease dipeptidyl peptidase 1 (DPP1), also known as cathepsin C (CatC), can suppress suppurative inflammation in vivo by blocking the processing of zymogenic (pro-) forms of neutrophil serine proteases (NSPs), including neutrophil elastase, proteinase 3, and cathepsin G. DPP1 also plays an important role in activating granzyme serine proteases that are expressed by cytotoxic T lymphocytes (CTL) and natural killer (NK) cells. Therefore, it is critical to determine whether DPP1 inhibition can also cause off-target suppression of CTL/NK-cell-mediated killing of virus-infected or malignant cells. Herein, we demonstrate that the processing of human granzymes A and B, transitioning from zymogen to active proteases, is not solely dependent on DPP1. Thus, the killing of target cells by primary human CD8+ T cells, NK cells, and gene-engineered anti-CD19 CAR T cells was not blocked in vitro even after prior exposure to high concentrations of the reversible DPP1 inhibitor brensocatib. Consistent with this observation, the turnover of model granzyme A/B peptide substrates in the human CTL/NK cell lysates was not significantly reduced by brensocatib. In contrast, preincubation with brensocatib almost entirely abolished (>90%) both the cytotoxic activity of mouse CD8+ T cells and granzyme substrate turnover. Overall, our finding that the effects of DPP1 inhibition on human cytotoxic lymphocytes are attenuated in comparison to those of mice indicates that granzyme processing/activation pathways differ between mice and humans. Moreover, the in vitro data suggest that human subjects treated with reversible DPP1 inhibitors, such as brensocatib, are unlikely to experience any appreciable deficits in CTL/NK-cell-mediated immunities.

Serine protease inhibitor, SerpinA3n, regulates cardiac remodelling after myocardial infarction

AIMS

Following myocardial infarction (MI), the heart repairs itself via a fibrotic repair response. The degree of fibrosis is determined by the balance between deposition of extracellular matrix (ECM) by activated fibroblasts and breakdown of nascent scar tissue by proteases that are secreted predominantly by inflammatory cells. Excessive proteolytic activity and matrix turnover has been observed in human heart failure, and protease inhibitors in the injured heart regulate matrix breakdown. Serine protease inhibitors (Serpins) represent the largest and the most functionally diverse family of evolutionary conserved protease inhibitors, and levels of the specific Serpin, SerpinA3, have been strongly associated with clinical outcomes in human MI as well as non-ischaemic cardiomyopathies. Yet, the role of Serpins in regulating cardiac remodelling is poorly understood. The aim of this study was to understand the role of Serpins in regulating scar formation after MI.

METHODS AND RESULTS

Using a SerpinA3n conditional knockout mice model, we observed the robust expression of Serpins in the infarcted murine heart and demonstrate that genetic deletion of SerpinA3n (mouse homologue of SerpinA3) leads to increased activity of substrate proteases, poorly compacted matrix, and significantly worse post-infarct cardiac function. Single-cell transcriptomics complemented with histology in SerpinA3n-deficient animals demonstrated increased inflammation, adverse myocyte hypertrophy, and expression of pro-hypertrophic genes. Proteomic analysis of scar tissue demonstrated decreased cross-linking of ECM peptides consistent with increased proteolysis in SerpinA3n-deficient animals.

CONCLUSION

Our study demonstrates a hitherto unappreciated causal role of Serpins in regulating matrix function and post-infarct cardiac remodelling.

Periodontal Effects of the Reversible Dipeptidyl Peptidase 1 Inhibitor Brensocatib in Bronchiectasis

AIMS

Brensocatib is a reversible inhibitor of dipeptidyl peptidase 1 (cathepsin C), in development to treat chronic non-cystic fibrosis bronchiectasis. The phase 2, randomized, placebo-controlled WILLOW trial (NCT03218917) was conducted to examine whether brensocatib reduced the incidence of pulmonary exacerbations. Brensocatib prolonged the time to the first exacerbation and led to fewer exacerbations than placebo. Because brensocatib potentially affects oral tissues due to its action on neutrophil-mediated inflammation, we analyzed periodontal outcomes in the trial participants.

MATERIALS AND METHODS

Patients with bronchiectasis were randomized 1:1:1 to receive once-daily oral brensocatib 10 or 25 mg or placebo. Periodontal status was monitored throughout the 24-week trial in a prespecified safety analysis. Periodontal pocket depth (PPD) at screening, week 8, and week 24 was evaluated. Gingival inflammation was evaluated by a combination of assessing bleeding upon probing and monitoring the Löe-Silness Gingival Index on 3 facial surfaces and the mid-lingual surface.

RESULTS

At week 24, mean ± SE PPD reductions were similar across treatment groups: -0.07 ± 0.007, -0.06 ± 0.007, and -0.15 ± 0.007 mm with brensocatib 10 mg, brensocatib 25 mg, and placebo, respectively. The distribution of changes in PPD and the number of patients with multiple increased PPD sites were similar across treatment groups at weeks 8 and 24. The frequencies of gingival index values were generally similar across treatment groups at each assessment. An increase in index values 0-1 and a decrease in index values 2-3 over time and at the end of the study were observed in all groups, indicating improved oral health.

CONCLUSIONS

In patients with non-cystic fibrosis bronchiectasis, brensocatib 10 or 25 mg had an acceptable safety profile after 6 months' treatment, with no changes in periodontal status noted. Improvement in oral health at end of the study may be due to regular dental care during the trial and independent of brensocatib treatment.

KNOWLEDGE TRANSFER STATEMENT

The results of this study suggest that 24 weeks of treatment with brensocatib does not affect periodontal disease progression. This information can be used by clinicians when considering treatment approaches for bronchiectasis and suggests that the use of brensocatib will not be limited by periodontal disease risks. Nevertheless, routine dental/periodontal care should be provided to patients irrespective of brensocatib treatment.

CRISPR-Cas9n-mediated ELANE promoter editing for gene therapy of severe congenital neutropenia

Severe congenital neutropenia (CN) is an inherited pre-leukemia bone marrow failure syndrome commonly caused by autosomal-dominant ELANE mutations (ELANE-CN). ELANE-CN patients are treated with daily injections of recombinant human granulocyte colony-stimulating factor (rhG-CSF). However, some patients do not respond to rhG-CSF, and approximately 15% of ELANE-CN patients develop myelodysplasia or acute myeloid leukemia. Here, we report the development of a curative therapy for ELANE-CN through inhibition of ELANE mRNA expression by introducing two single-strand DNA breaks at the opposing DNA strands of the ELANE promoter TATA box using CRISPR-Cas9D10A nickases-termed MILESTONE. This editing effectively restored defective neutrophil differentiation of ELANE-CN CD34+ hematopoietic stem and progenitor cells (HSPCs) in vitro and in vivo, without affecting the functions of the edited neutrophils. CRISPResso analysis of the edited ELANE-CN CD34+ HSPCs revealed on-target efficiencies of over 90%. Simultaneously, GUIDE-seq, CAST-Seq, and rhAmpSeq indicated a safe off-target profile with no off-target sites or chromosomal translocations. Taken together, ex vivo gene editing of ELANE-CN HSPCs using MILESTONE in the setting of autologous stem cell transplantation could be a universal, safe, and efficient gene therapy approach for ELANE-CN patients.

Neutrophil extracellular trap formation and its implications in nonsteroidal anti-inflammatory drug-induced small intestinal injury

BACKGROUND AND AIM

Nonsteroidal anti-inflammatory drugs (NSAIDs) damage the small intestine via neutrophil infiltration driven by the mucosal invasion of enterobacteria. The antimicrobial function of neutrophils is partially dependent on neutrophil extracellular traps (NETs). Excessive NET formation has been associated with several inflammatory diseases. Here, we aimed to investigate the role of NETs in NSAID-induced small intestinal damage using human samples and an experimental mouse model.

METHODS

Human small intestine specimens were obtained from NSAID users during double-balloon enteroscopy. Wild-type, protein arginine deiminase 4 (PAD4) knockout, and antibiotic-treated mice were administered indomethacin to induce small intestinal injury. The expression of NET-associated proteins, including PAD4, citrullinated histone H3 (CitH3), cell-free DNA, and myeloperoxidase (MPO), was evaluated.

RESULTS

The double-positive stained area with CitH3 and MPO, which is specific for neutrophil-derived extracellular traps, was significantly high in the injured small intestinal mucosa of NSAID users. In a mouse model, small intestinal damage developed at 6 h after indomethacin administration, accompanied by increased mRNA levels of interleukin-1β and keratinocyte chemoattractant and elevated NET-associated protein levels of PAD4, CitH3, and MPO in small intestine and serum levels of cell-free DNA. Both genetic deletion and pharmacological inhibition of PAD4 attenuated this damage by reducing the mRNA expression of inflammatory cytokines and NET-associated proteins. Furthermore, mice pretreated with antibiotics showed resistance to indomethacin-induced small intestinal damage, with less NET formation.

CONCLUSION

These results suggest that NETs aggravate NSAID-induced small intestinal injury. Therefore, NET inhibition could be a potential treatment for NSAID-induced small intestinal injury.

Inflammatory proteins and neutrophil extracellular traps increase in burn blister fluid 24h after burn

Burn wound blister fluid is a valuable matrix for understanding the biological pathways associated with burn injury. In this study, 152 blister fluid samples collected from paediatric burn wounds at three different hospitals were analysed using mass spectrometry proteomic techniques. The protein abundance profile at different days after burn indicated more proteins were associated with cellular damage/repair in the first 24 h, whereas after this point more proteins were associated with antimicrobial defence. The inflammatory proteins persisted at a high level in the blister fluid for more than 7 days. This may indicate that removal of burn blisters prior to two days after burn is optimal to prevent excessive or prolonged inflammation in the wound environment. Additionally, many proteins associated with the neutrophil extracellular trap (NET) pathway were increased after burn, further implicating NETs in the post-burn inflammatory response. NET inhibitors may therefore be a potential treatment to reduce post-burn inflammation and coagulation pathology and enhance burn wound healing outcomes.

Metabolic Dysfunction-Associated Steatohepatitis Detected by Neutrophilic Crown-Like Structures in Morbidly Obese Patients: A Multicenter and Clinicopathological Study

Metabolic dysfunction-associated steatohepatitis (MASH) is the progressive form of metabolic dysfunction-associated steatotic liver disease (MASLD), and closely associated with a high risk of liver-related morbidity and mortality. Although enhanced neutrophil infiltration of the liver is a histological hallmark of MASH, the morphological pattern of hepatic neutrophils and their relevance to the definition of MASH remain unknown. This clinicopathological study aimed to determine the association of neutrophilic crown-like structures (CLSs) in liver biopsies and evaluate their relevance to the histological diagnosis of MASH. A total of 483 morbidly obese adults who underwent bariatric surgery were recruited. Neutrophilic CLSs in liver biopsies were detected by immunohistochemistry for neutrophil elastase and proteinase 3. All participants were classified into 4 histological subgroups: no MASLD (118, 24.4%), MASLD (76, 15.7%), borderline MASH (185, 38.3%), and definite MASH (104, 21.5%). In the discovery cohort (n = 379), the frequency of neutrophilic CLSs increased in line with the severity of liver disease. The number of neutrophilic CLSs was positively correlated with established histological characteristics of MASH. At a cutoff value of <0.3 per 20× microscopic field, the number of neutrophilic CLSs yielded a robust diagnostic accuracy to discriminate no MASLD and MASLD from borderline MASH and definite MASH; a cutoff at >1.3 per 20× microscopic field exhibited a statistically significant accuracy to distinguish definite MASH from other groups (no MASLD, MASLD, and borderline MASH). The significance of neutrophilic CLSs in identifying borderline MASH and definite MASH was confirmed in an external validation cohort (n = 104). The frequency of neutrophilic CLSs was significantly higher than that of macrophagic CLSs. In conclusion, neutrophilic CLSs in the liver represent a typical histological characteristic of MASH and may serve as a promising indicator to improve the diagnostic accuracy of MASH during histological assessment of liver biopsies.

Neutrophil-Derived Proteases in Lung Inflammation: Old Players and New Prospects

Neutrophil-derived proteases are critical to the pathology of many inflammatory lung diseases, both chronic and acute. These abundant enzymes play roles in key neutrophil functions, such as neutrophil extracellular trap formation and reactive oxygen species release. They may also be released, inducing tissue damage and loss of tissue function. Historically, the neutrophil serine proteases (NSPs) have been the main subject of neutrophil protease research. Despite highly promising cell-based and animal model work, clinical trials involving the inhibition of NSPs have shown mixed results in lung disease patients. As such, the cutting edge of neutrophil-derived protease research has shifted to proteases that have had little-to-no research in neutrophils to date. These include the cysteine and serine cathepsins, the metzincins and the calpains, among others. This review aims to outline the previous work carried out on NSPs, including the shortcomings of some of the inhibitor-orientated clinical trials. Our growing understanding of other proteases involved in neutrophil function and neutrophilic lung inflammation will then be discussed. Additionally, the potential of targeting these more obscure neutrophil proteases will be highlighted, as they may represent new targets for inhibitor-based treatments of neutrophil-mediated 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.

CBP/P300 BRD Inhibition Reduces Neutrophil Accumulation and Activates Antitumor Immunity in TNBC

Tumor-associated neutrophils (TANs) have been shown to promote immunosuppression and tumor progression, and a high TAN frequency predicts poor prognosis in triple-negative breast cancer (TNBC). Dysregulation of CREB binding protein (CBP)/P300 function has been observed with multiple cancer types. The bromodomain (BRD) of CBP/P300 has been shown to regulate its activity. In this study, we found that IACS-70654, a novel and selective CBP/P300 BRD inhibitor, reduced TANs and inhibited the growth of neutrophil-enriched TNBC models. In the bone marrow, CBP/P300 BRD inhibition reduced the tumor-driven abnormal differentiation and proliferation of neutrophil progenitors. Inhibition of CBP/P300 BRD also stimulated the immune response by inducing an IFN response and MHCI expression in tumor cells and increasing tumor-infiltrated CTLs. Moreover, IACS-70654 improved the response of a neutrophil-enriched TNBC model to docetaxel and immune checkpoint blockade. This provides a rationale for combining a CBP/P300 BRD inhibitor with standard-of-care therapies in future clinical trials for neutrophil-enriched TNBC.

Summary

In neutrophil-enriched triple-negative breast cancer (TNBC) models, CREB binding protein (CBP)/P300 bromodomain (BRD) inhibition reduces tumor growth and systemic neutrophil accumulation while stimulating an antitumor immune response. This improves standard-of-care therapies, suggesting a potential therapeutic benefit of CBP/P300 BRD inhibitors for neutrophil-enriched TNBC.

Neutrophil proteases are protective against SARS-CoV-2 by degrading the spike protein and dampening virus-mediated inflammation

Studies on severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2) have highlighted the crucial role of host proteases for viral replication and the immune response. The serine proteases furin and TMPRSS2 and lysosomal cysteine proteases facilitate viral entry by limited proteolytic processing of the spike (S) protein. While neutrophils are recruited to the lungs during COVID-19 pneumonia, little is known about the role of the neutrophil serine proteases (NSPs) cathepsin G (CatG), elastase (NE), and proteinase 3 (PR3) on SARS-CoV-2 entry and replication. Furthermore, the current paradigm is that NSPs may contribute to the pathogenesis of severe COVID-19. Here, we show that these proteases cleaved the S protein at multiple sites and abrogated viral entry and replication in vitro. In mouse models, CatG significantly inhibited viral replication in the lung. Importantly, lung inflammation and pathology were increased in mice deficient in NE and/or CatG. These results reveal that NSPs contribute to innate defenses against SARS-CoV-2 infection via proteolytic inactivation of the S protein and that NE and CatG limit lung inflammation in vivo. We conclude that therapeutic interventions aiming to reduce the activity of NSPs may interfere with viral clearance and inflammation in COVID-19 patients.

Bovine neutrophils kill the sexually-transmitted parasite Tritrichomonas foetus using trogocytosis

The protozoan parasite Tritrichomonas foetus (T. foetus) is the causative organism of bovine trichomonosis (also referred to as trichomoniasis), a sexually-transmitted infection that reduces fertility in cattle. Efforts to control trichomonosis on cattle farms are hindered by the discouragement of antibiotic use in agriculture, and the incomplete, short-lived protection conferred by the current vaccines. A more complete mechanistic understanding of what effective immunity to T. foetus entails could enable the development of more robust infection control strategies. While neutrophils, the primary responders to infection, are present in infected tissues and have been shown to kill the parasite in vitro, the mechanism they use for parasite killing has not been established. Here, we show that primary bovine neutrophils isolated from peripheral blood rapidly kill T. foetus in vitro in a dose-dependent manner, and that optimal parasite killing is reduced by inhibitors of trogocytosis. We also use imaging to show that bovine neutrophils surround T. foetus and trogocytose its membrane. These findings are consistent with killing via trogocytosis, a recently described novel neutrophil antimicrobial mechanism.

Advances of presepsin in sepsis-associated ARDS

This article reviews the correlation between presepsin and sepsis and the resulting acute respiratory distress syndrome (ARDS). ARDS is a severe complication of sepsis. Despite the successful application of protective mechanical ventilation, restrictive fluid therapy, and neuromuscular blockade, which have effectively reduced the morbidity and mortality associated with ARDS, the mortality rate among patients with sepsis-associated ARDS remains notably high. The challenge lies in the prediction of ARDS onset and the timely implementation of intervention strategies. Recent studies have demonstrated significant variations in presepsin (PSEP) levels between patients with sepsis and those without, particularly in the context of ARDS. Moreover, these studies have revealed substantially elevated PSEP levels in patients with sepsis-associated ARDS compared to those with nonsepsis-associated ARDS. Consequently, PSEP emerges as a valuable biomarker for identifying patients with an increased risk of sepsis-associated ARDS and to predict in-hospital mortality.

Targeted Library of Phosphonic-Type Inhibitors of Human Neutrophil Elastase

Despite many years of research, human neutrophil elastase (HNE) still remains an area of interest for many researchers. This multifunctional representative of neutrophil serine proteases is one of the most destructive enzymes found in the human body which can degrade most of the extracellular matrix. Overexpression or dysregulation of HNE may lead to the development of several inflammatory diseases. Previously, we presented the HNE inhibitor with kinact/KI value over 2,000,000 [M-1s-1]. In order to optimize its structure, over 100 novel tripeptidyl derivatives of α-aminoalkylphosphonate diaryl esters were synthesized, and their activity toward HNE was checked. To confirm the selectivity of the resultant compounds, several of the most active were additionally checked against the two other neutrophil proteases: proteinase 3 and cathepsin G. The developed modifications allowed us to obtain a compound with significantly increased inhibitory activity against human neutrophil elastase with high selectivity toward cathepsin G, but none toward proteinase 3.

Sivelestat ameliorates sepsis-induced myocardial dysfunction by activating the PI3K/AKT/mTOR signaling pathway

The cardioprotective role of sivelestat, a neutrophil elastase inhibitor, has already been demonstrated, but the underlying molecular mechanism remains unclear. This study aimed to explore the mechanism underlying the role of sivelestat in sepsis-induced myocardial dysfunction (SIMD). We found that sivelestat treatment remarkably improved the viability and suppressed the apoptosis of lipopolysaccharide (LPS)-stimulated H9c2 cells. In vivo, sivelestat treatment was associated with an improved survival rate; reduced serum cTnT, TNF-α, IL-1β levels and myocardial TNF-α and IL-1β levels; ameliorated cardiac function and structure; and reduced cardiomyocyte apoptosis. Moreover, sivelestat treatment substantially increased Bcl-2 expression and suppressed caspase-3 and Bax expression in LPS-induced H9c2 cells and in the heart tissues of septic rats. Furthermore, the phosphatidylinositol 3-kinase/protein kinase B/mechanistic target of rapamycin (PI3K/AKT/mTOR) signaling pathway was activated both in vitro and in vivo. The protective effect of sivelestat against SIMD was reversed by the PI3K inhibitor LY294002. In summary, sivelestat can protect against SIMD by activating the PI3K/AKT/mTOR signaling pathway.

Glymphatic System Pathology and Neuroinflammation as Two Risk Factors of Neurodegeneration

The key to the effective treatment of neurodegenerative disorders is a thorough understanding of their pathomechanism. Neurodegeneration and neuroinflammation are mutually propelling brain processes. An impairment of glymphatic system function in neurodegeneration contributes to the progression of pathological processes. The question arises as to how neuroinflammation and the glymphatic system are related. This review highlights the direct and indirect influence of these two seemingly independent processes. Protein aggregates, a characteristic feature of neurodegeneration, are correlated with glymphatic clearance and neuroinflammation. Glial cells cannot be overlooked when considering the neuroinflammatory processes. Astrocytes are essential for the effective functioning of the glymphatic system and play a crucial role in the inflammatory responses in the central nervous system. It is imperative to acknowledge the significance of AQP4, a protein that exhibits a high degree of polarization in astrocytes and is crucial for the functioning of the glymphatic system. AQP4 influences inflammatory processes that have not yet been clearly delineated. Another interesting issue is the gut-brain axis and microbiome, which potentially impact the discussed processes. A discussion of the correlation between the functioning of the glymphatic system and neuroinflammation may contribute to exploring the pathomechanism of neurodegeneration.

The proteolytic airway environment associated with pneumonia acts as a barrier for treatment with anti-infective antibodies

Like pneumonia, coronavirus disease 2019 (COVID-19) is characterized by a massive infiltration of innate immune cells (such as polymorphonuclear leukocytes) into the airways and alveolar spaces. These cells release proteases that may degrade therapeutic antibodies and thus limit their effectiveness. Here, we investigated the in vitro and ex vivo impact on anti-severe acute respiratory syndrome coronavirus 2 (SARS-CoV2) IgG1s and other IgG subclasses (IgG2 and IgG4) of the neutrophil elastase, proteinase 3 and cathepsin G (the three main neutrophil serine proteases) found in endotracheal aspirates from patients with severe COVID-19. Although the IgGs were sensitive to neutrophil serine proteases, IgG2 was most resistant to proteolytic degradation. The two anti-SARS CoV2 antibodies (casirivimab and imdevimab) were sensitive to the lung's proteolytic environment, although neutrophil serine protease inhibitors only partly limited the degradation. Overall, our results show that the pneumonia-associated imbalance between proteases and their inhibitors in the airways contributes to degradation of antiviral antibodies.

Chemotactic Micro/Nanomotors for Biomedical Applications

In nature, many organisms respond chemotactically to external chemical stimuli in order to extract nutrients or avoid danger. Inspired by this natural chemotaxis, micro/nanomotors with chemotactic properties have been developed and applied to study a variety of disease models. This chemotactic strategy has shown promising results and has attracted the attention of an increasing number of researchers. This paper mainly reviews the construction methods of different types of chemotactic micro/nanomotors, the mechanism of chemotaxis, and the potential applications in biomedicine. First, based on the classification of materials, the construction methods and therapeutic effects of chemotactic micro/nanomotors based on natural cells and synthetic materials in cellular and animal experiments will be elaborated in detail. Second, the mechanism of chemotaxis of micro/nanomotors is elaborated in detail: chemical reaction induced chemotaxis and physical process driven chemotaxis. In particular, the main differences and significant advantages between chemotactic micro/nanomotors and magnetic, electrical and optical micro/nanomotors are described. The applications of chemotactic micro/nanomotors in the biomedical fields in recent years are then summarized, focusing on the mechanism of action and therapeutic effects in cancer and cardiovascular disease. Finally, the authors are looking forward to the future development of chemotactic micro/nanomotors in the biomedical fields.

Global Remodeling of Host Proteome in Response to Leishmania Infection

The protozoan parasite Leishmania possesses an intrinsic ability to modulate a multitude of pathways in the host, toward aiding its own proliferation. In response, the host reprograms its cellular, immunological, and metabolic machinery to evade the parasite's lethal impact. Besides inducing various antioxidant signaling pathways to counter the elevated stress response proteins like heme oxygenase-1 (HO-1), Leishmania also attempts to delay host cell apoptosis by promoting anti-apoptotic proteins like Bcl-2. The downstream modulation of apoptotic proteins is regulated by effector pathways, including the PI3K/Akt survival pathway, the mitogen-activated protein kinases (MAPKs) signaling pathway, and STAT phosphorylation. In addition, Leishmania assists in its infection in a time-dependent manner by modulating the level of various proteins of autophagic machinery. Immune effector cells, such as mast cells and neutrophils, entrap and kill the pathogen by secreting various granular proteins. In contrast, the host macrophages exert their leishmanicidal effect by secreting various cytokines, such as IL-2, IL-12, etc. An interplay of various signaling pathways occurs in an organized network that is highly specific to both pathogen and host species. This Review analyzes the modulation of expression of proteins, including the cytokines, providing a realistic approach toward understanding the pathophysiology of disease and predicting some prominent markers for disease intervention and vaccine support strategies.

Elevated first-trimester neutrophil elastase and proteinase 3 increase the risk of gestational diabetes mellitus and adverse fetal outcomes

BACKGROUND

Chronic inflammation plays a vital role in the development of gestational diabetes mellitus (GDM). Studies in mouse models show that neutrophil serine proteases (NSPs), neutrophil elastase (NE) and proteinase-3 (PR3) are important drivers of chronic inflammation with consequent metabolic disturbances. This study evaluated the association of NE and PR3 with GDM development and adverse fetal outcomes.

METHOD(S)

This was a prospective cohort study. Serum PR3 and NE concentration was measured in all enrolled pregnant women in the first and the second trimester to determine the connection between NSPs and GDM and adverse fetal outcomes. Logistic regression, spline regression and linear regression analyses were applied to investigate the association of NE or PR3 with GDM development and adverse fetal outcomes. The concentration of NE and PR3 in placental biopsies was evaluated by semi-quantitative analysis of immunohistochemistry staining.

RESULT(S)

NE or PR3 concentration in the first trimester, rather than the second, increased more significantly in women with GDM than in those without, regardless of pre-pregnancy body mass index and age. There was a stepwise increase in GDM occurrence as well as comprehensive adverse fetal outcomes across tertiles of NE and PR3. NE and PR3 were positively associated with neutrophil count, pre-pregnancy BMI, plasma glucose level and newborn weight. Logistic regression revealed NE or PR3 to be independent risk factors for the development of GDM and comprehensive adverse fetal outcomes. Spline regression showed a significant increased risk of GDM occurrence and comprehensive adverse fetal outcomes when serum NE concentration exceeded 417.60 ng/mL and a similar result for PR3 and GDM occurrence when the latter exceeded 88.52 ng/mL. Immunohistochemistry data confirmed that enriched NE and PR3 content in placental tissue may have contributed to the development of GDM.

CONCLUSION(S)

This work demonstrates that excessive first-trimester NE and PR3 increase the risk of GDM development and comprehensive adverse fetal outcomes.

Congenital neutropenia: From lab bench to clinic bedside and back

Neutropenia is a hematological condition characterized by a decrease in absolute neutrophil count (ANC) in peripheral blood, typically classified in adults as mild (1-1.5 × 109/L), moderate (0.5-1 × 109/L), or severe (< 0.5 × 109/L). It can be categorized into two types: congenital and acquired. Congenital severe chronic neutropenia (SCN) arises from mutations in various genes, with different inheritance patterns, including autosomal recessive, autosomal dominant, and X-linked forms, often linked to mitochondrial diseases. The most common genetic cause is alterations in the ELANE gene. Some cases exist as non-syndromic neutropenia within the SCN spectrum, where genetic origins remain unidentified. The clinical consequences of congenital neutropenia depend on granulocyte levels and dysfunction. Infants with this condition often experience recurrent bacterial infections, with approximately half facing severe infections within their first six months of life. These infections commonly affect the respiratory system, digestive tract, and skin, resulting in symptoms like fever, abscesses, and even sepsis. The severity of these symptoms varies, and the specific organs and systems affected depend on the genetic defect. Congenital neutropenia elevates the risk of developing acute myeloid leukemia (AML) or myelodysplastic syndromes (MDS), particularly with certain genetic variants. SCN patients may acquire CSF3R and RUNX1 mutations, which can predict the development of leukemia. It is important to note that high-dose granulocyte colony-stimulating factor (G-CSF) treatment may have the potential to promote leukemogenesis. Treatment for neutropenia involves antibiotics, drugs that boost neutrophil production, or bone marrow transplants. Immediate treatment is essential due to the heightened risk of severe infections. In severe congenital or cyclic neutropenia (CyN), the primary therapy is G-CSF, often combined with antibiotics. The G-CSF dosage is gradually increased to normalize neutrophil counts. Hematopoietic stem cell transplants are considered for non-responders or those at risk of AML/MDS. In cases of WHIM syndrome, CXCR4 inhibitors can be effective. Future treatments may involve gene editing and the use of the diabetes drug empagliflozin to alleviate neutropenia symptoms.

Mechanistic study on the anti-proinflammatory activity of Kunitz type inhibitor from Caesalpinia decapetala seeds

The study reports the biochemical characterization and mechanism of action of a novel 19.6 kDa protease inhibitor (PIs) isolated from the seeds of Caesalpinia decapetala belonging to the Fabaceae family. A systematic study was performed to ascertain the purity, specificity, biochemical and structural characterization, and its potential in curbing inflammation in vitro conditions. A two-step chromatography technique was used to purify the PIs. Sodium dodecyl sulfate polyacrylamide gel electrophoresis and matrix-assisted laser desorption ionization time of flight were employed to detect the molecular mass of the protein. N-terminal sequence analysis of the inhibitor showed sequence similarity with the Kunitz family PIs. The in vitro test tube assay was performed for determining the anti-inflammatory activity and the inhibitor is antiproliferative against macrophage (RAW264.7) and lung cancer cell lines (A549). An effective decrease in the release of inflammatory mediators (NO, IL-6, TNF-α) and on the activity of elastase was observed in macrophage cell lines (RAW264.7) which were treated with PIs. The purified inhibitor shows promising results against inflammation.

Oral vancomycin treatment suppresses gut trypsin activity and preserves intestinal barrier function during EAE

Studies have reported increased intestinal permeability in multiple sclerosis (MS) patients and its mouse model experimental autoimmune encephalomyelitis (EAE). However, the mechanisms driving increased intestinal permeability that in turn exacerbate neuroinflammation during EAE remain unclear. Here we showed that vancomycin preserved the integrity of the intestinal barrier, while also suppressing gut trypsin activity, enhancing the relative abundance of specific Lactobacilli and ameliorating disease during EAE. Furthermore, Lactobacilli enriched in the gut of vancomycin-treated EAE mice at day 3 post immunization negatively correlated with gut trypsin activity and EAE severity. In untreated EAE mice, we observed increased intestinal permeability and increased intestinal protease activated receptor 2 (PAR2) expression at day 3 post immunization. Prior studies have shown that trypsin increases intestinal permeability by activating PAR2. Our results suggest that the interaction between intestinal PAR2 and trypsin may be a key modulator of intestinal permeability and disease severity during EAE.

Type 2 Cystatins and Their Roles in the Regulation of Human Immune Response and Cancer Progression

Cystatins are a family of intracellular and extracellular protease inhibitors that inhibit cysteine cathepsins-a group of lysosomal cysteine proteases that participate in multiple biological processes, including protein degradation and post-translational cleavage. Cysteine cathepsins are associated with the development of autoimmune diseases, tumor progression, and metastasis. Cystatins are categorized into three subfamilies: type 1, type 2, and type 3. The type 2 cystatin subfamily is the largest, containing 10 members, and consists entirely of small secreted proteins. Although type 2 cystatins have many shared biological roles, each member differs in structure, post-translational modifications (e.g., glycosylation), and expression in different cell types. These distinctions allow the type 2 cystatins to have unique biological functions and properties. This review provides an overview of type 2 cystatins, including their biological similarities and differences, their regulatory effect on human immune responses, and their roles in tumor progression, immune evasion, and metastasis.

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.

Gas Chromatography-Mass Spectrometry Reveals Stage-Specific Metabolic Signatures of Ankylosing Spondylitis

Ankylosing spondylitis (AS) is a type of chronic rheumatic immune disease, and the crucial point of AS treatment is identifying the correct stage of the disease. However, there is a lack of effective diagnostic methods for AS staging. The primary objective of this study was to perform an untargeted metabolomic approach in AS patients in an effort to reveal metabolic differences between patients in remission and acute stages. Serum samples from 40 controls and 57 AS patients were analyzed via gas chromatography-mass spectrometry (GC-MS). Twenty-four kinds of differential metabolites were identified between the healthy controls and AS patients, mainly involving valine/leucine/isoleucine biosynthesis and degradation, phenylalanine/tyrosine/tryptophan biosynthesis, glutathione metabolism, etc. Furthermore, the levels of fatty acids (linoleate, dodecanoate, hexadecanoate, and octadecanoate), amino acids (serine and pyroglutamate), 2-hydroxybutanoate, glucose, etc., were lower in patients in the acute stage than those in the remission stage, which may be associated with the aggravated inflammatory response and elevated oxidative stress in the acute stage. Multiple stage-specific metabolites were significantly correlated with inflammatory indicators (CRP and ESR). In addition, the combination of serum 2-hydroxybutanoate and hexadecanoate plays a significant role in the diagnosis of AS stages. These metabolomics-based findings provide new perspectives for AS staging, treatment, and pathogenesis studies.

E-64c-Hydrazide Based Cathepsin C Inhibitors: Optimizing the Interactions with the S1'-S2' Area

The zymogens of the neutrophil serine proteases elastase, proteinase 3, and cathepsin G are converted proteolytically into their pro-inflammatory active forms by the action of cathepsin C. The inhibition of this cysteine protease therefore is an interesting therapeutic approach for the treatment of inflammatory disorders with a high neutrophil burden such as COPD. Based on E-64c-hydrazide as lead structure, we have recently developed a covalently acting cathepsin C inhibitor using a n-butyl residue attached at the amine nitrogen of the hydrazide moiety to efficiently address the deep hydrophobic S2 pocket. To further optimize the affinity and selectivity profile of this inhibitor, the S1'-S2' area was now investigated by a combinatorial approach, showing that Nle-tryptamide is a ligand superior to the initially used Leu-isoamylamide. Using the neutrophil precursor line U937 as a cell culture model, this optimized inhibitor blocks the intracellular cathepsin C activity and thereby suppresses the activation of neutrophil elastase.

A Review of the Relationship between the Immune Response, Inflammation, Oxidative Stress, and the Pathogenesis of Sickle Cell Anaemia

Sickle cell anaemia (SCD) is a life-threatening haematological disorder which is predominant in sub-Saharan Africa and is triggered by a genetic mutation of the β-chain haemoglobin gene resulting in the substitution of glutamic acid with valine. This mutation leads to the production of an abnormal haemoglobin molecule called haemoglobin S (HbS). When deoxygenated, haemoglobin S (HbS) polymerises and results in a sickle-shaped red blood cell which is rigid and has a significantly shortened life span. Various reports have shown a strong link between oxidative stress, inflammation, the immune response, and the pathogenesis of sickle cell disease. The consequence of these processes leads to the development of vasculopathy (disease of the blood vessels) and several other complications. The role of the immune system, particularly the innate immune system, in the pathogenesis of SCD has become increasingly clear in recent years of research; however, little is known about the roles of the adaptive immune system in this disease. This review examines the interaction between the immune system, inflammation, oxidative stress, blood transfusion, and their effects on the pathogenesis of sickle cell anaemia.

Role of neutrophils in different stages of atherosclerosis

Neutrophils constitute the first line of defense in human immunity and can be attracted to inflamed and infected sites by various chemokines. As essential players in immune processes, neutrophils theoretically play integral roles in the course of chronic inflammation-induced atherosclerosis. However, because neutrophils are rarely found in atherosclerotic lesions, their involvement in the pathophysiological progression of atherosclerosis has been largely underestimated or ignored. Recent research has revealed convincing evidence showing the presence of neutrophils in atherosclerotic lesions and has revealed neutrophil contributions to different atherosclerosis stages in mice and humans. This review describes the underlying mechanisms of neutrophils in different stages of atherosclerosis and highlights potential neutrophil-targeted therapeutic strategies relevant to atherosclerosis. An in-depth understanding of neutrophils' roles in atherosclerosis pathology will promote exploration of new methods for the prevention and treatment of atherogenesis and atherothrombosis.

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.

Profound structural conservation of chemically cross-linked HIV-1 envelope glycoprotein experimental vaccine antigens

Chemical cross-linking is used to stabilize protein structures with additional benefits of pathogen and toxin inactivation for vaccine use, but its use has been restricted by the potential for local or global structural distortion. This is of particular importance when the protein in question requires a high degree of structural conservation for inducing a biological outcome such as the elicitation of antibodies to conformationally sensitive epitopes. The HIV-1 envelope glycoprotein (Env) trimer is metastable and shifts between different conformational states, complicating its use as a vaccine antigen. Here we have used the hetero-bifunctional zero-length reagent 1-Ethyl-3-(3-Dimethylaminopropyl)-Carbodiimide (EDC) to cross-link two soluble Env trimers, selected well-folded trimer species using antibody affinity, and transferred this process to good manufacturing practice (GMP) for experimental medicine use. Cross-linking enhanced trimer stability to biophysical and enzyme attack. Cryo-EM analysis revealed that cross-linking retained the overall structure with root-mean-square deviations (RMSDs) between unmodified and cross-linked Env trimers of 0.4-0.5 Å. Despite this negligible distortion of global trimer structure, we identified individual inter-subunit, intra-subunit, and intra-protomer cross-links. Antigenicity and immunogenicity of the trimers were selectively modified by cross-linking, with cross-linked ConS retaining bnAb binding more consistently than ConM. Thus, the EDC cross-linking process improves trimer stability whilst maintaining protein folding, and is readily transferred to GMP, consistent with the more general use of this approach in protein-based vaccine design.

Research Progress of Neutrophil-Mediated Drug Delivery Strategies for Inflammation-Related Disease

As the most abundant white blood cells in humans, neutrophils play a key role in acute and chronic inflammation, suggesting that these cells are a key component of targeted therapies for various inflammation-related diseases. Specific enzyme-responsive or specific ligand-modified polymer nanoparticles are beneficial for improving drug efficacy, reducing toxicity, and enhancing focal site retention. However, there remain significant challenges in biomedical applications of these synthetic polymer nanoparticles, mainly due to their rapid clearance by the reticuloendothelial system. In recent years, biomimetic drug delivery systems such as neutrophils acting directly as drug carriers or neutrophil-membrane-coated nanoparticles have received increasing attention due to the natural advantages of neutrophils. Thus, neutrophil-targeted, neutrophil-assisted, or neutrophil-coated nanoparticles exhibit a prolonged blood circulation time and improved accumulation at the site of inflammation. Despite recent advancements, further clinical research must be performed to evaluate neutrophil-based delivery systems for future biomedical application in the diagnosis and treatment of related inflammatory diseases. In this review, we have summarized new exciting developments and challenges in neutrophil-mediated drug delivery strategies for treating inflammation-related diseases.

Neutrophils and neutrophil extracellular traps in cancer: promising targets for engineered nanomaterials

Neutrophils are the most abundant white blood cells in circulation and constitute up to 60% of circulating leukocytes. Neutrophils play a significant role in host defense against pathogens through various mechanisms, including phagocytosis, production of antimicrobial proteins, and formation of neutrophil extracellular traps (NETs). Recently, the role of neutrophils and NETs in cancer has generated significant interest, as accumulating evidence suggests that neutrophils and NETs contribute to cancer progression and are associated with adverse patient outcomes. In this review, we will first highlight the roles of neutrophils and NETs in cancer progression and metastasis and discuss new drug delivery approaches to target and modulate neutrophils and NETs for cancer therapeutics.

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.

Comprehensive Comparison of the Capacity of Functionalized Sepharose, Magnetic Core, and Polystyrene Nanoparticles to Immuno-Precipitate Procalcitonin from Human Material for the Subsequent Quantification by LC-MS/MS

Sepsis is a life-threatening organ dysfunction caused by a dysregulated host response to infection. The fast and accurate diagnosis of sepsis by procalcitonin (PCT) has emerged as an essential tool in clinical medicine. Although in use in the clinical laboratory for a long time, PCT quantification has not yet been standardized. The International Federation of Clinical Chemistry working group on the standardization of PCT (IFCC-WG PCT) aims to provide an LC-MS/MS-based reference method as well as the highest metrological order reference material to address this diagnostic need. Here, we present the systematic evaluation of the efficiency of an immuno-enrichment method, based on functionalized Sepharose, magnetic-core, or polystyrene (latex) nano-particles, to quantitatively precipitate PCT from different human sample materials. This method may be utilized for both mass spectrometric and proteomic purposes. In summary, only magnetic-core nano-particles functionalized by polyclonal PCT antibodies can fulfil the necessary requirements of the international standardization of PCT. An optimized method proved significant benefits in quantitative and specific precipitation as well as in the subsequent LC-MS/MS detection of PCT in human serum samples or HeLa cell extract. Based on this finding, further attempts of the PCT standardization process will utilize a magnetic core-derived immuno-enrichment step, combined with subsequent quantitative LC-MS/MS detection.

Exploring the role of neutrophils in infectious and noninfectious pulmonary disorders

With the change in global environment, respiratory disorders are becoming more threatening to the health of people all over the world. These diseases are closely linked to performance of immune system. Within the innate arm of immune system, Neutrophils are an important moiety to serve as an immune defense barrier. They are one of the first cells recruited to the site of infection and plays a critical role in pathogenesis of various pulmonary diseases. It is established that the migration and activation of neutrophils can lead to inflammation either directly or indirectly and this inflammation caused is very crucial for the clearance of pathogens and resolution of infection. However, the immunopathological mechanisms involved to carry out the same is very complex and not well understood. Despite there being studies concentrating on the role of neutrophils in multiple respiratory diseases, there is still a long way to go in order to completely understand the complexity of the participation of neutrophils and mechanisms involved in the development of these respiratory diseases. In the present article, we have reviewed the literature to comprehensively provide an insight in the current development and advancements about the role of neutrophils in infectious respiratory disorders including viral respiratory disorders such as Coronavirus disease (COVID-19) and bacterial pulmonary disorders with a focused review on pulmonary tuberculosis as well as in noninfectious disorders like Chronic obstructive pulmonary disease (COPD) and asthma. Also, future directions into research and therapeutic targets have been discussed for further exploration.

High yield expression in Pichia pastoris of human neutrophil elastase fused to cytochrome B5

Recombinant human neutrophil elastase (rHNE), a serine protease, was expressed in Pichia pastoris. Glycosylation sites were removed via bioengineering to prevent hyper-glycosylation (a common problem with this system) and the cDNA was codon optimized for translation in Pichia pastoris. The zymogen form of rHNE was secreted as a fusion protein with an N-terminal six histidine tag followed by the heme binding domain of Cytochrome B5 (CytB5) linked to the N-terminus of the rHNE sequence via an enteropeptidase cleavage site. The CytB5 fusion balanced the very basic rHNE (pI = 9.89) to give a colored fusion protein (pI = 6.87), purified via IMAC. Active rHNE was obtained via enteropeptidase cleavage, and purified via cation exchange chromatography, resulting in a single protein band on SDS PAGE (Mr = 25 KDa). Peptide mass fingerprinting analysis confirmed the rHNE amino acid sequence, the absence of glycosylation and the absence of an 8 amino acid C-terminal peptide as opposed to the 20 amino acids usually missing from the C-terminus of native enzyme. The yield of active rHNE was 0.41 mg/L of baffled shaker flask culture medium. Active site titration with alpha-1 antitrypsin, a potent irreversible elastase inhibitor, quantified the concentration of purified active enzyme. The Km of rHNE with methoxy-succinyl-AAPVpNA was identical with that of the native enzyme within the assay's limit of accuracy. This is the first report of full-length rHNE expression at high yields and low cost facilitating further studies on this major human neutrophil enzyme.

Complete non-proline backbone resonance assignments of the S. aureus neutrophil serine protease inhibitor, EapH1

The S. aureus extracellular adherence protein (Eap) and its homologs, EapH1 and EapH2, serve roles in evasion of the human innate immune system. EapH1 binds with high-affinity and inhibits the neutrophil azurophilic granule proteases neutrophil elastase, cathepsin-G and proteinase-3. Previous structural studies using X-ray crystallography have shown that EapH1 binds to neutrophil elastase and cathepsin-G using a globally similar binding mode. However, whether the same holds true in solution is unknown and whether the inhibitor experiences dynamic changes following binding remains uncertain. To facilitate solution-phase structural and biochemical studies of EapH1 and its complexes with neutrophil granule proteases, we have characterized EapH1 by multidimensional NMR spectroscopy. Here we report a total of 100% of the non-proline backbone resonance assignments of EapH1 with BMRB accession number 50,304.

The Effects of 1-O-Acetylbritannilactone Isolated from Inula britannica Flowers on Human Neutrophil Elastase and Inflammation of RAW 264.7 Cells and Zebrafish Larvae

During a search for natural inflammatory inhibitors, 1-O-acetylbritannilactone (ABL), a sesquiterpene lactone, was isolated from the flowers of Inula britannica. ABL significantly inhibited human neutrophil elastase (HNE) with a half-maximal inhibitory concentration (IC₅₀) of 3.2 ± 0.3 µM, thus did so more effectively than the positive control material (epigallocatechin gallate) (IC₅₀ 7.2 ± 0.5 µM). An enzyme kinetic study was performed. ABL noncompetitively inhibited HNE with an inhibition constant K_i of 2.4 µM. ABL inhibited lipopolysaccharide-induced nitric oxide and prostaglandin E₂ production by RAW 264.7 cells in a dose-dependent manner, as well as the protein-level expression of inducible nitric oxide synthase and cyclooxygenase-2. The anti-inflammatory effect of ABL was confirmed using a transgenic Tg(mpx:EGFP) zebrafish larval model. The exposure of the larvae to ABL inhibited neutrophil recruitment to the site of injury after tail fin amputation.