GPR97 triggers inflammatory processes in human neutrophils via a macromolecular complex upstream of PAR2 activation

Neutrophils play essential anti-microbial and inflammatory roles in host defense, however, their activities require tight regulation as dysfunction often leads to detrimental inflammatory and autoimmune diseases. Here we show that the adhesion molecule GPR97 allosterically activates CD177-associated membrane proteinase 3 (mPR3), and in conjugation with several protein interaction partners leads to neutrophil activation in humans. Crystallographic and deletion analysis of the GPR97 extracellular region identified two independent mPR3-binding domains. Mechanistically, the efficient binding and activation of mPR3 by GPR97 requires the macromolecular CD177/GPR97/PAR2/CD16b complex and induces the activation of PAR2, a G protein-coupled receptor known for its function in inflammation. Triggering PAR2 by the upstream complex leads to strong inflammatory activation, prompting anti-microbial activities and endothelial dysfunction. The role of the complex in pathologic inflammation is underscored by the finding that both GPR97 and mPR3 are upregulated on the surface of disease-associated neutrophils. In summary, we identify a PAR2 activation mechanism that directs neutrophil activation, and thus inflammation. The PR3/CD177/GPR97/PAR2/CD16b protein complex, therefore, represents a potential therapeutic target for neutrophil-mediated inflammatory diseases.

Cadmium induces apoptosis by miR-9-5p targeting PTEN and regulates the PI3K/AKT pathway in the piglet adrenal gland

Cadmium (Cd) is an environmental pollutant that can cause endocrine organ damage. To explore the effect of subacute CdCl₂ exposure on piglet adrenal gland tissue and its mechanism based on the establishment of this model, bioinformatics, TUNEL assay, western blot (WB), and qRT-PCR methods were used to detect related indicators. The results showed that after Cd exposure, antioxidant enzymes decreased, heat shock protein increased, and miR-9-5p-gene of phosphatase and tensin homolog (PTEN) upregulates the phosphatidylinositol-3-kinase (PI3K/AKT) pathway. After this pathway was activated, the expression of the apoptosis-related factors cysteinyl aspartate-specific proteinase 3 and 9 (caspase 3 and 9), B-cell lymphoma-2-associated X (BAX) was increased sharply, and the expression of B-cell lymphoma-2 (BCL2) was significantly decreased. The changes in these indicators indicate that Cd exposure induces apoptosis and causes tissue damage in the adrenal gland of piglets. This study aims to reveal the toxic effects of CdCl₂ in animals and will provide new ideas for the toxicology of Cd.

[Effect of Tetrastigma hemsleyanum on sepsis and mechanism based on network pharmacology and experimental verification]

Based on network pharmacology and in vivo experiment, this study explored the therapeutic effect of Tetrastigma hemsle-yanum(SYQ) on sepsis and the underlying mechanism. The common targets of SYQ and sepsis were screened out by network pharmacology, and the "SYQ-component-target-sepsis" network was constructed. The protein-protein interaction(PPI) network was established by STRING. Gene Ontology(GO) term enrichment and Kyoto Encyclopedia of Genes and Genomes(KEGG) pathway enrichment were performed based on DAVID to predict the anti-sepsis mechanism of SYQ. The prediction results of network pharmacology were verified by animal experiment. The network pharmacology results showed that the key anti-sepsis targets of SYQ were tumor necrosis factor(TNF), interleukin(IL)-6, IL-1β, IL-10, and cysteinyl asparate specific proteinase 3(caspase-3), which were mainly involved in Toll-like receptor 4(TLR4)/myeloid differentiation factor 88(MyD88)/nuclear factor kappaB(NF-κB) signaling pathway. The results of animal experiment showed that SYQ can decrease the content of C-reactive protein(CRP), procalcitonin(PCT), lactate dehydrogenase(LDH), IL-6, TNF-α, and IL-1β, increase the content of IL-10, and down-regulate the protein levels of Bcl-2-associa-ted X(Bax)/B-cell lymphoma 2(Bcl2), cleaved caspase-3, TLR4, MyD88, and p-NF-κB p65/NF-κB p65. In summary, SYQ plays an anti-inflammatory role in the treatment of sepsis by acting on the key genes related to inflammation and apoptosis, such as TNF-α, IL-6, IL-lβ, IL-10, Bax, Bcl2, and cleaved caspase-3. The mechanism is the likelihood that it suppresses the TLR4/MyD88/NF-κB signaling pathway, which verifies relative prediction results of network pharmacology.

Origin and Expansion of the Serine Protease Repertoire in the Myelomonocyte Lineage

The deepest evolutionary branches of the trypsin/chymotrypsin family of serine proteases are represented by the digestive enzymes of the gastrointestinal tract and the multi-domain proteases of the blood coagulation and complement system. Similar to the very old digestive system, highly diverse cleavage specificities emerged in various cell lineages of the immune defense system during vertebrate evolution. The four neutrophil serine proteases (NSPs) expressed in the myelomonocyte lineage, neutrophil elastase, proteinase 3, cathepsin G, and neutrophil serine protease 4, collectively display a broad repertoire of (S1) specificities. The origin of NSPs can be traced back to a circulating liver-derived trypsin-like protease, the complement factor D ancestor, whose activity is tightly controlled by substrate-induced activation and TNFα-induced locally upregulated protein secretion. However, the present-day descendants are produced and converted to mature enzymes in precursor cells of the bone marrow and are safely sequestered in granules of circulating neutrophils. The potential site and duration of action of these cell-associated serine proteases are tightly controlled by the recruitment and activation of neutrophils, by stimulus-dependent regulated secretion of the granules, and by various soluble inhibitors in plasma, interstitial fluids, and in the inflammatory exudate. An extraordinary dynamic range and acceleration of immediate defense responses have been achieved by exploiting the high structural plasticity of the trypsin fold.

Proteinase 3 Autoreactivity in Anti-Neutrophil Cytoplasmic Antibody-associated vasculitis-Immunological versus clinical features

ANCA-associated vasculitis (AAV) is a group of chronic inflammatory diseases of small- and medium-sized vessels, which are broadly subdivided based on organ manifestations and disease-specific autoantibodies. The so called anti-neutrophil cytoplasmic antibodies (ANCA) mostly target one of the enzymes, proteinase 3 (PR3) or myeloperoxidase (MPO). Accumulating genetic data demonstrates that these two autoantibodies discriminate two distinct disease entities, more so than the clinical subdivision which is mainly criteria-based. Treatment of AAV includes heavy immunosuppression and is guided by which organs that are involved. Generally, patients with PR3-ANCA display higher risk for disease relapse than patients with MPO-ANCA. In this review, we will focus on the autoimmune features of PR3+ AAV and our current understanding of its triggers and the potential translation into clinical practice.

Anti-proteinase 3-positive Eosinophilic Granulomatosis with Polyangiitis Revealed by Cardiac Tamponade

Eosinophilic granulomatosis with polyangiitis (EGPA) is a rare systemic vasculitis characterized by asthma, eosinophilia, and diffuse eosinophilic infiltration. Although cardiovascular involvement is common and a leading cause of EGPA-related mortality, severe pericarditis-led cardiac tamponade occurs rarely. We herein report a 72-year-old man with anti-proteinase 3 (anti-PR3) anti-neutrophil cytoplasmic antibody (ANCA)-positive EGPA diagnosed by the presence of cardiac tamponade, which responded quickly to pericardiocentesis and a single administration of prednisolone. This is the first case of anti-PR3 ANCA-positive EGPA with cardiac tamponade; the patient displayed clinical features of both ANCA-positive and ANCA-negative cases.

Expression of serine proteases in neutrophils from women and men: Regulation by endocrine disruptor bisphenol A

Bisphenol A (BPA) is a well-known endocrine disruptor. However, little information is available about its immunological effects. In the present study, we aimed to evaluate cytotoxic activity of BPA on human polymorphonuclear neutrophils (PMNs) according to gender and examine its effect on the expression of neutrophil serine proteases. Results indicated that exposure to BPA (above 16 μM) leads to a decrease in viability of PMNs and to morphological changes in these cells of both genders. The experiments showed different effects of BPA on the expression of proteinase 3, elastase, and cathepsin G in PMNs of both men and women, depending on the gender and concentration used. Thus, our findings suggest for the first time that through dysregulation of the expression of these enzymes, BPA may lead to disorders of the nonspecific cellular response in people exposed to this xenoestrogen.

IgG4:IgG RNA ratio differentiates active disease from remission in granulomatosis with polyangiitis: a new disease activity marker? A cross-sectional and longitudinal study

OBJECTIVES

An important limitation in granulomatosis with polyangiitis (GPA) is the lack of disease activity markers. Immunoglobulin G4-positive (IgG4+) B cells and plasma cells are implicated in the pathogenesis of GPA. We hypothesized that the presence of these cells in peripheral blood could serve as disease activity parameter in GPA.

METHODS

We included 35 proteinase 3-antineutrophil cytoplasmic antibodies-positive patients with GPA in a cross-sectional study. Active disease was defined as Birmingham Vasculitis Activity Score (BVAS) ≥ 3 (n = 15), remission as BVAS of 0 (n = 17), and low disease activity (LDA) as BVAS of 1-2 and clinical remission (n = 3). Healthy subjects (n = 10), patients with systemic lupus erythematosus (n = 24), and patients with rheumatoid arthritis (n = 19) functioned as control subjects. An additional longitudinal study was performed in ten patients with GPA. Using a validated qPCR test, we measured the IgG4:IgG RNA ratio in all groups and compared the results with known biomarkers.

RESULTS

The median qPCR score was higher in active GPA (21.4; IQR 12.1-29.6) than in remission/LDA (3.3; IQR 1.6-5.6) (Mann-Whitney U test, p < 0.0001) and outperformed other known disease activity parameters in detecting activity. A cutoff qPCR score of 11.2% differentiated active disease from remission/LDA accurately (AUC 0.993). The qPCR test correlated well with the BVAS (Spearman r = 0.77, p < 0.0001). In the longitudinal study, a decrease in BVAS correlated with qPCR score reduction (paired t test, p < 0.05).

CONCLUSIONS

The IgG4:IgG RNA ratio in GPA accurately distinguishes active disease from remission and correlates well with disease activity in these single-center studies. If these results are confirmed in larger longitudinal studies, this test might help to steer treatment decisions in patients with GPA.

Local enrichment of fatty acid-binding protein 4 in the pericardial cavity of cardiovascular disease patients

BACKGROUND

The pericardial fluid may be representative of the interstitium of the heart. The aim of this study was to discriminate in cardiovascular disease patients between adipocytokines that are produced locally by the heart and those supplied by the circulation.

METHODS

Enzyme-linked immunosorbent assays (ELISA) were used to determine levels of N-terminal pro-brain natriuretic peptide (NT-pBNP), fatty acid-binding protein 4 (FABP4), leptin, lipocalin-2, neutrophil elastase, proteinase-3, high sensitivity C-reactive protein (hsCRP) and adiponectin in venous plasma and pericardial fluid harvested during elective cardio-thoracic surgery (n = 132-152).

RESULTS

In pericardial fluid compared to plasma, the levels were significantly smaller (p < 0.001) for leptin, lipocalin-2, neutrophil elastase, proteinase-3, hsCRP and adiponectin. For these biomarkers, the ratio of pericardial fluid-to-plasma level ([PF]/[P], median (interquartile range)) was 0.65 (0.47-1.01), 0.78 (0.56-1.09), 0.23 (0.11-0.60), 0.17 (0.09-0.36), 0.14 (0.08-0.35), and 0.25 (0.15-0.34), respectively. In contrast, pericardial fluid was significantly enriched (p < 0.001) in NT-pBNP ([PF]/[P]: 1.9 (1.06-2.73)) and even more so for FABP4 ([PF]/[P]: 3.90 (1.47-9.77)). Moreover, in pericardial fluid, the adipocytokines interrelated all significantly positive and correlated negative to hsCRP, whereas for NT-pBNP only a significantly positive correlation with adiponectin was found. These interrelations were distinct from those in the plasma, as were the correlations of the pericardial biomarkers with patient characteristics compared to plasma.

CONCLUSIONS

In cardiovascular disease patients, the pericardial cavity is a distinct adipocytokine microenvironment in which especially FABP4 is mainly derived from the heart.

Proteinase 3; a potential target in chronic obstructive pulmonary disease and other chronic inflammatory diseases

Chronic Obstructive Pulmonary Disease (COPD) is a common, multifactorial lung disease which results in significant impairment of patients' health and a large impact on society and health care burden. It is believed to be the result of prolonged, destructive neutrophilic inflammation which results in progressive damage to lung structures. During this process, large quantities of neutrophil serine proteinases (NSPs) are released which initiate the damage and contribute towards driving a persistent inflammatory state.Neutrophil elastase has long been considered the key NSP involved in the pathophysiology of COPD. However, in recent years, a significant role for Proteinase 3 (PR3) in disease development has emerged, both in COPD and other chronic inflammatory conditions. Therefore, there is a need to investigate the importance of PR3 in disease development and hence its potential as a therapeutic target. Research into PR3 has largely been confined to its role as an autoantigen, but PR3 is involved in triggering inflammatory pathways, disrupting cellular signalling, degrading key structural proteins, and pathogen response.This review summarises what is presently known about PR3, explores its involvement particularly in the development of COPD, and indicates areas requiring further investigation.

Epithelial proteome profiling suggests the essential role of interferon-inducible proteins in patients with allergic rhinitis

BACKGROUND

Seasonal allergic rhinitis (SAR) caused by intermittent exposure to seasonal pollen causes itching, nasal congestion, and repeated sneezing, with profound effects on quality of life, work productivity, and school performance. Although both the genotype and environmental factors can contribute to the immunologic basis of allergic reactions, the molecular underpinnings associated with the pathogenesis of allergic rhinitis are not entirely clear.

METHODS

To address these questions, nasal epithelial brushings were collected from 29 patients with SAR and 31 control subjects during and after the pollen season. We then implemented an orbitrap-based, bottom-up, label-free quantitative proteomics approach, followed by multivariate analyses to identify differentially abundant (DA) proteins among the 4 sample groups.

RESULTS

We identified a total of 133 DA proteins for which the most significantly overrepresented functional category was found to be interferon 1 signaling. Two proteins, cystatin 1 and myeloblastin, the former of which protects against protease activity of allergens and the latter with a role in epithelial barrier function, were DA in patients with SAR and control subjects, irrespective of season. Moreover, interferon-inducible protein with tetratricopeptide repeats 1, cystatin 1, and interferon-inducible protein with tetratricopeptide repeats 3 were found to be differentially regulated between patients with SAR and control subjects, with inverse abundance dynamics during the transition from fall to spring.

CONCLUSION

We identified type 1 interferon-regulated proteins as biomarkers in patients with SAR, potentially playing an important role in its pathogenesis. Moreover, when compared with patients with SAR, healthy subjects exhibit an antagonistic proteomic response across seasons, which might prove to be a therapeutic target for disease prevention.

Neutrophils and neutrophil serine proteases are increased in the spleens of estrogen-treated C57BL/6 mice and several strains of spontaneous lupus-prone mice

Estrogen, a natural immunomodulator, regulates the development and function of diverse immune cell types. There is now renewed attention on neutrophils and neutrophil serine proteases (NSPs) such as neutrophil elastase (NE), proteinase 3 (PR3), and cathepsin G (CG) in inflammation and autoimmunity. In this study, we found that although estrogen treatment significantly reduced total splenocytes number, it markedly increased the splenic neutrophil absolute numbers in estrogen-treated C57BL/6 (B6) mice when compared to placebo controls. Concomitantly, the levels of NSPs and myeloperoxidase (MPO) were highly upregulated in the splenocytes from estrogen-treated mice. Despite the critical role of NSPs in the regulation of non-infectious inflammation, by employing NE^-/-/PR3^-/-/CG^-/- triple knock out mice, we demonstrated that the absence of NSPs affected neither estrogen’s ability to increase splenic neutrophils nor the induction of inflammatory mediators (IFNγ, IL-1β, IL-6, TNFα, MCP-1, and NO) from ex vivo activated splenocytes. Depletion of neutrophils in vitro in splenocytes with anti-Ly6G antibody also had no obvious effect on NSP expression or LPS-induced IFNγ and MCP-1. These data suggest that estrogen augments NSPs, which appears to be independent of enhancing ex vivo inflammatory responses. Since estrogen has been implicated in regulating several experimental autoimmune diseases, we extended our observations in estrogen-treated B6 mice to spontaneous autoimmune-prone female MRL-lpr, B6-lpr and NZB/W_F1 mice. There was a remarkable commonality with regards to the increase of neutrophils and concomitant increase of NSPs and MPO in the splenic cells of different strains of autoimmune-prone mice and estrogen-treated B6 mice. Collectively, since NSPs and neutrophils are involved in diverse pro-inflammatory activities, these data suggest a potential pathologic implication of increased neutrophils and NSPs that merits further investigation.

Alterations in nuclear structure promote lupus autoimmunity in a mouse model

Systemic lupus erythematosus (SLE) is an autoimmune disorder characterized by the development of autoantibodies that recognize components of the cell nucleus. The vast majority of lupus research has focused on either the contributions of immune cell dysfunction or the genetics of the disease. Because granulocytes isolated from human SLE patients had alterations in neutrophil nuclear morphology that resembled the Pelger-Huet anomaly, and had prominent mis-splicing of mRNA encoding the nuclear membrane protein lamin B receptor (LBR), consistent with their Pelger-Huet-like nuclear morphology, we used a novel mouse model system to test the hypothesis that a disruption in the structure of the nucleus itself also contributes to the development of lupus autoimmunity. The lupus-prone mouse strain New Zealand White (NZW) was crossed with c57Bl/6 mice harboring a heterozygous autosomal dominant mutation in Lbr (B6.Lbr(ic/+)), and the (NZW×B6.Lbr(ic))F1 offspring were evaluated for induction of lupus autoimmunity. Only female (NZW×B6.Lbr(ic))F1 mice developed lupus autoimmunity, which included splenomegaly, kidney damage and autoantibodies. Kidney damage was accompanied by immune complex deposition, and perivascular and tubule infiltration of mononuclear cells. The titers of anti-chromatin antibodies exceeded those of aged female MRL-Fas(lpr) mice, and were predominantly of the IgG2 subclasses. The anti-nuclear antibody staining profile of female (NZW×B6.Lbr(ic))F1 sera was complex, and consisted of an anti-nuclear membrane reactivity that colocalized with the A-type lamina, in combination with a homogeneous pattern that was related to the recognition of histones with covalent modifications that are associated with gene activation. An anti-neutrophil IgM recognizing calreticulin, but not myeloperoxidase (MPO) or proteinase 3 (PR3), was also identified. Thus, alterations in nuclear structure contribute to lupus autoimmunity when expressed in the context of a lupus-prone genetic background, suggesting a mechanism for the development of lupus autoimmunity in genetically predisposed individuals that is induced by the disruption of nuclear architecture.

Proteases and protease inhibitors of urinary extracellular vesicles in diabetic nephropathy

Diabetic nephropathy (DN) is one of the major complications of diabetes mellitus (DM), leads to chronic kidney disease (CKD), and, ultimately, is the main cause for end-stage kidney disease (ESKD). Beyond urinary albumin, no reliable biomarkers are available for accurate early diagnostics. Urinary extracellular vesicles (UEVs) have recently emerged as an interesting source of diagnostic and prognostic disease biomarkers. Here we used a protease and respective protease inhibitor array to profile urines of type 1 diabetes patients at different stages of kidney involvement. Urine samples were divided into groups based on the level of albuminuria and UEVs isolated by hydrostatic dialysis and screened for relative changes of 34 different proteases and 32 protease inhibitors, respectively. Interestingly, myeloblastin and its natural inhibitor elafin showed an increase in the normo- and microalbuminuric groups. Similarly, a characteristic pattern was observed in the array of protease inhibitors, with a marked increase of cystatin B, natural inhibitor of cathepsins L, H, and B as well as of neutrophil gelatinase-associated Lipocalin (NGAL) in the normoalbuminuric group. This study shows for the first time the distinctive alterations in comprehensive protease profiles of UEVs in diabetic nephropathy and uncovers intriguing mechanistic, prognostic, and diagnostic features of kidney damage in diabetes.

Increased neutrophil elastase and proteinase 3 and augmented NETosis are closely associated with β-cell autoimmunity in patients with type 1 diabetes

Type 1 diabetes (T1D) is an autoimmune disease resulting from the self-destruction of insulin-producing β-cells. Reduced neutrophil counts have been observed in patients with T1D. However, the pathological roles of neutrophils in the development of T1D remain unknown. Here we show that circulating protein levels and enzymatic activities of neutrophil elastase (NE) and proteinase 3 (PR3), both of which are neutrophil serine proteases stored in neutrophil primary granules, were markedly elevated in patients with T1D, especially those with disease duration of less than 1 year. Furthermore, circulating NE and PR3 levels increased progressively with the increase of the positive numbers and titers of the autoantibodies against β-cell antigens. An obvious elevation of NE and PR3 was detected even in those autoantibody-negative patients. Increased NE and PR3 in T1D patients are closely associated with elevated formation of neutrophil extracellular traps. By contrast, the circulating levels of α1-antitrypsin, an endogenous inhibitor of neutrophil serine proteases, are decreased in T1D patients. These findings support an early role of neutrophil activation and augmented neutrophil serine proteases activities in the pathogenesis of β-cell autoimmunity and also suggest that circulating NE and PR3 may serve as sensitive biomarkers for the diagnosis of T1D.

Proteinase 3-dependent caspase-3 cleavage modulates neutrophil death and inflammation

Caspase-3-mediated spontaneous death in neutrophils is a prototype of programmed cell death and is critical for modulating physiopathological inflammatory responses; however, the underlying regulatory pathways remain ill defined. Here we determined that in aging neutrophils, the cleavage and activation of caspase-3 is independent of the canonical caspase-8- or caspase-9-mediated pathway. Instead, caspase-3 activation was mediated by serine protease proteinase 3 (PR3), which is present in the cytosol of aging neutrophils. Specifically, PR3 cleaved procaspase-3 at a site upstream of the canonical caspase-9 cleavage site. In mature neutrophils, PR3 was sequestered in granules and released during aging via lysosomal membrane permeabilization (LMP), leading to procaspase-3 cleavage and apoptosis. Pharmacological inhibition or knockdown of PR3 delayed neutrophil death in vitro and consistently delayed neutrophil death and augmented neutrophil accumulation at sites of inflammation in a murine model of peritonitis. Adoptive transfer of both WT and PR3-deficient neutrophils revealed that the delayed death of neutrophils lacking PR3 is due to an altered intrinsic apoptosis/survival pathway, rather than the inflammatory microenvironment. The presence of the suicide protease inhibitor SERPINB1 counterbalanced the protease activity of PR3 in aging neutrophils, and deletion of Serpinb1 accelerated neutrophil death. Taken together, our results reveal that PR3-mediated caspase-3 activation controls neutrophil spontaneous death.

Phosphoinositide 3-kinase inhibition restores neutrophil accuracy in the elderly: toward targeted treatments for immunosenescence

Immunosenescence is the functional deterioration of the immune system during natural aging. Despite increased susceptibility to bacterial infections in older adults, age-associated changes to neutrophil responses are only partially understood, and neutrophil migration has not been characterized in detail. Here we describe reduced chemotaxis but preserved chemokinesis toward a range of inflammatory stimuli in migrating neutrophils isolated from healthy older subjects. Cross-sectional data indicate that migratory behavior changes in the sixth decade of life. Crucially, aberrant migration may increase "bystander" tissue damage and heighten inflammation as a result of excess proteinase release during inaccurate chemotaxis, as well as reducing pathogen clearance. We show evidence of increased neutrophil proteinase activity in older adults, namely, raised levels of neutrophil proteinase substrate-derived peptides and evidence of primary granule release, associated with increased systemic inflammation. Inaccurate migration was causally associated with increased constitutive phosphoinositide 3-kinase (PI3K) signaling; untreated neutrophils from old donors demonstrated significant PI3K activation compared with cells from young donors. PI3K-blocking strategies, specifically inhibition of PI3Kγ or PI3Kδ, restored neutrophil migratory accuracy, whereas SHIP1 inhibition worsened migratory flaws. Targeting PI3K signaling may therefore offer a new strategy in improving neutrophil functions during infections and reduce inappropriate inflammation in older patients.

Using a Caesalpinia echinata Lam. protease inhibitor as a tool for studying the roles of neutrophil elastase, cathepsin G and proteinase 3 in pulmonary edema

Acute lung injury (ALI) is characterized by neutrophil infiltration and the release of proteases, mainly elastase (NE), cathepsin G (Cat G) and proteinase 3 (PR3), which can be controlled by specific endogenous inhibitors. However, inhibitors of these proteases have been isolated from different sources, including plants. For this study, CeEI, or Caesalpinia echinata elastase inhibitor, was purified from C. echinata (Brazil-wood) seeds after acetone fractionation, followed by ion exchange and reversed phase chromatographic steps. Characterization with SDS-PAGE, stability assays, amino acid sequencing and alignment with other protein sequences confirmed that CeEI is a member of the soybean Kunitz trypsin inhibitor family. Like other members of this family, CeEI is a 20 kDa monomeric protein; it is stable within a large pH and temperature range, with four cysteine residues forming two disulfide bridges, conserved amino acid residues and leucine-isoleucine residues in the reactive site. CeEI was able to inhibit NE and Cat G at a nanomolar range (with K(i)s of 1.9 and 3.6 nM, respectively) and inhibited PR3 within a micromolar range (K(i) 3.7 μM), leading to hydrolysis of specific synthetic substrates. In a lung edema model, CeEI reduced the lung weight and pulmonary artery pressure until 180 min after the injection of zymosan-activated polymorphonuclear neutrophils. In experiments performed in the presence of a Cat G and PR3, but not an NE inhibitor, lung edema was reduced only until 150 min and pulmonary artery pressure was similar to that of the control. These results confirm that NE action is crucial to edema establishment and progression. Additionally, CeEI appears to be a useful tool for studying the physiology of pulmonary edema and provides a template for molecular engineering and drug design for ALI therapy.

[Neurological involvement in Wegener's granulomatosis]

Abstract Wegener's granulomatosis is a rare autoimmune disease associated with granulomatous inflammation and anti-neutrophil cytoplasmic antibody (ANCA)-associated small vessel vasculitis. Following the discovery of ANCA, ANCA-associated vasculitis is established as a disease entity of Wegener's granulomatosis, microscopic polyangiitis, and Churg-Strauss syndrome. Clinical and experimental studies have provided evidences that myeloperoxidase (MPO) and proteinase 3 (PR3), which are major antigenic targets for ANCA in neutrophils, are not only disease markers but also involved in the pathogenesis. In addition, recent studies have revealed another potential antigen for ANCA, lysosomal-associated membrane protein-2 (LAMP-2). Though nervous system manifestations of Wegener's granulomatosis are less frequent than classical manifestations in the lungs and kidneys, 20-50% of patients demonstrate neurological involvements. Peripheral nervous system involvement (in generalized Wegener's granulomatosis) is more frequent than central nervous system (CNS) involvement. Multiple mononeuropathy and multiple cranial neuropathy are the most prevalent symptoms. CNS manifestations include cerebrovascular events, pachymeningitis, seizures, and reversible posterior leukoencephalopathy syndrome. Here we discuss the pathogenic mechanism of ANCA and review the literature regarding neurological involvement in Wegener's granulomatosis.

Global substrate profiling of proteases in human neutrophil extracellular traps reveals consensus motif predominantly contributed by elastase

Neutrophil extracellular traps (NETs) consist of antimicrobial molecules embedded in a web of extracellular DNA. Formation of NETs is considered to be a defense mechanism utilized by neutrophils to ensnare and kill invading pathogens, and has been recently termed NETosis. Neutrophils can be stimulated to undergo NETosis ex vivo, and are predicted to contain high levels of serine proteases, such as neutrophil elastase (NE), cathepsin G (CG) and proteinase 3 (PR3). Serine proteases are important effectors of neutrophil-mediated immunity, which function directly by degrading pathogenic virulent factors and indirectly via proteolytic activation or deactivation of cytokines, chemokines and receptors. In this study, we utilized a diverse and unbiased peptide library to detect and profile protease activity associated with NETs induced by phorbol-12-myristate-13-acetate (PMA). We obtained a “proteolytic signature” from NETs derived from healthy donor neutrophils and used proteomics to assist in the identification of the source of this proteolytic activity. In addition, we profiled each neutrophil serine protease and included the newly identified enzyme, neutrophil serine protease 4 (NSP4). Each enzyme had overlapping yet distinct endopeptidase activities and often cleaved at unique sites within the same peptide substrate. The dominant proteolytic activity in NETs was attributed to NE; however, cleavage sites corresponding to CG and PR3 activity were evident. When NE was immunodepleted, the remaining activity was attributed to CG and to a lesser extent PR3 and NSP4. Our results suggest that blocking NE activity would abrogate the major protease activity associated with NETs. In addition, the newly identified substrate specificity signatures will guide the design of more specific probes and inhibitors that target NET-associated proteases.

Variables of host response in saliva of patients with periodontitis: a pilot study

OBJECTIVE

Periodontitis is an infection that results from an imbalance between periodontopathic microorganisms and the local and systemic host defense. This study analyzed saliva samples of patients with periodontitis for several biomarkers of host response.

METHOD AND MATERIALS

Saliva was collected from 13 patients with chronic periodontitis, seven patients with aggressive periodontitis, and 13 periodontally healthy control subjects. Diverse markers of host response representing innate and adaptive immune response as well as antioxidative variables were determined.

RESULTS

Patients with aggressive periodontitis had significantly higher values of lipid peroxidation and cathepsin C activity in saliva. The highest activities of neutrophil elastase, proteinase 3, and superoxide dismutase were measured in chronic periodontitis patients. Levels of antimicrobial peptides HNPs 1-3 were significantly highest in chronic periodontitis patients than in aggressive periodontitis or control subjects. Immunoglobulin G levels directed against Aggregatibacter actinomycetemcomitans were highest in aggressive periodontitis patients, while those directed against Porphyromonas gingivalis were highest in chronic periodontitis patients. Immunoglobulin A levels directed against these periodontopathogens did not differ among the groups.

CONCLUSION

Chronic periodontitis patients showed higher levels of markers primarily associated with combating infection. The levels of markers known mainly for tissue damage were higher in aggressive periodontitis patients. Neutrophil-related markers may be able to identify and differentiate patients with periodontitis.

PR3 and elastase alter PAR1 signaling and trigger vWF release via a calcium-independent mechanism from glomerular endothelial cells

Neutrophil proteases, proteinase-3 (PR3) and elastase play key roles in glomerular endothelial cell (GEC) injury during glomerulonephritis. Endothelial protease-activated receptors (PARs) are potential serine protease targets in glomerulonephritis. We investigated whether PAR1/2 are required for alterations in GEC phenotype that are mediated by PR3 or elastase during active glomerulonephritis. Endothelial PARs were assessed by flow cytometry. Thrombin, trypsin and agonist peptides for PAR1 and PAR2, TFLLR-NH(2) and SLIGKV-NH(2,) respectively, were used to assess alterations in PAR activation induced by PR3 or elastase. Endothelial von Willebrand Factor (vWF)release and calcium signaling were used as PAR activation markers. Both PR3 and elastase induced endothelial vWF release, with elastase inducing the highest response. PAR1 peptide induced GEC vWF release to the same extent as PR3. However, knockdown of PARs by small interfering RNA showed that neither PAR1 nor PAR2 activation caused PR3 or elastase-mediated vWF release. Both proteases interacted with and disarmed surface GEC PAR1, but there was no detectable interaction with cellular PAR2. Neither protease induced a calcium response in GEC. Therefore, PAR signaling and serine protease-induced alterations in endothelial function modulate glomerular inflammation via parallel but independent pathways.

Expression profile of proinflammatory genes in neutrophil-enriched granulocytes stimulated with native anti-PR3 autoantibodies

Granulomatosis with polyangiitis (Wegener's ) is a rare autoimmune disease associated with the presence of antibodies directed against neutrophil antigen, proteinase-3 (PR3). The mechanisms by which anti-neutrophil cytoplasmic antibodies (ANCA) may activate neutrophils are still not well understood. In the present study we analyzed neutrophil gene expression profile after anti-PR3 antibodies stimulation. Briefly neutrophils isolated from 12 healthy volunteers, who tested negative for anti-PR3 autoantibodies, were stimulated with anti-PR3 IgG and activation of 147 genes was analyzed with the use of TaqMan low-density arrays. In stimulated neutrophils we observed up-regulation of 13 genes (CCL2, CXCL2, VCAM1, MMP9, PLCB4, PDE4C, PLA2G4C, RAC1, RHOA, IRAK1, CACNA1D, CACNB2, PTGDR), further 11 genes were up-regulated only in some donors (IL13, PF4, IL2RG, ITGB1, CD83, PLA2G7, ALOX12, AXNA1, AXNA5, LTA4H, MCR2) yet two others (HRH3 and PLA2G2D) were up-regulated in a few samples and undetectable in others. The obtained results demonstrate that c-ANCA mediated activation of neutrophils involve several pathways mediated via FcγRs like calcium signaling, phosphatidylinositol 3-kinase AKT pathway or MAPK signaling systems, but also inducts others, like G-protein signaling. Neutrophil is a very sensitive cell, responding to many environment changes. As our results showed, some anti-PR3 responses are highly variable across donors. Perhaps, this variablity also contribute to the susceptibility for granulocyte vasculitis and requires future studies.

KRAS mutation is associated with elevated myeloblastin activity in human lung adenocarcinoma

Lung cancer is the leading cause of all cancer deaths worldwide with suboptimal prognosis and treatment options. Therefore this study aimed to identify molecular characteristics with a predictive clinical utility which at the same time might represent novel therapeutic targets for human lung adenocarcinoma. Within this study mutations of v-Ki-RAS2 Kirsten rat sarcoma viral oncogene homolog (KRAS), a gene frequently mutated in lung adenocarcinoma, and their association with enzymatic activities, as assessed by activity-based proteomics, of members of the serine hydrolase (SH) superfamily, a large class of enzymes that have previously been linked to cancer was investigated. The results revealed that the activity of myeloblastin was significantly altered in the lung adenocarcinoma biopsies harboring a KRAS gene mutation. In conclusion myeloblastin is a potential therapeutic target for human lung adenocarcinoma, indicating that the combination of activity-based proteomics with mutational analysis is a valid approach for the discovery of novel biomarkers.

Towards a four-dimensional view of neutrophils

Neutrophils are constitutively produced throughout adult life and are essential for host responses to many types of pathogen. Neutropenia has long been associated with poor prognosis in the clinic, yet we have an incomplete understanding of their life cycle, not only during homeostasis but also during infection and chronic inflammation. Here, we review recent advances that provide insight into the genetic and biochemical regulators of neutrophil production, function, and survival.

Measurement of neutrophil elastase, proteinase 3, and cathepsin G activities using intramolecularly quenched fluorogenic substrates

Neutrophil elastase, proteinase 3, and cathepsin G are three hematopoietic serine proteases, large quantities of which are stored in neutrophil cytoplasmic azurophilic granules. They act in combination with reactive oxygen species to degrade engulfed microorganisms inside phagolysosomes. Active forms of these proteases are also externalized during neutrophil activation at inflammatory sites, thus helping to regulate inflammatory and immune responses. A fraction of secreted neutrophil serine proteases (NSPs) remains bound to the external plasma membrane, where they remain enzymatically active. This protocol describes the spectrofluorometric measurement of NSP activities using sensitive ortho-aminobenzoyl-peptidyl-N-(2,4-dinitrophenyl) ethylenediamine fluorescence resonance energy transfer (FRET) substrates that fully discriminate between the three human NSPs. These are used to measure subnanomolar concentrations of free or membrane-bound NSPs in low-binding microplates and to quantify the activities of individual proteases in biological fluids. We describe the synthesis of FRET substrate, neutrophil purification, and kinetic experiments on activated neutrophils. The protocol for measuring NSP activity on the surface of activated neutrophils can be adapted to measure NSP activities in whole biological fluids. Such data clarify the contributions of individual NSPs to the development of inflammatory diseases. Ultimately, these proteases may be shown to be targets for therapeutic inhibitors.

Neutrophil proteinase 3 induces diabetes in a mouse model of glucose tolerance

Type 1 diabetes is considered to be an autoimmune disease in which T cells attack pancreatic islet cells. Impaired glucose tolerance with type 2 diabetes has been classified as an obesity-associated metabolic syndrome. However, recent studies have revealed that type 2 diabetes is an autoinflammatory disease due to an imbalance of inflammatory cytokine production and related molecular components that cause inflammation. Insulin-like growth factor (IGF) and the insulin-like growth factor-binding protein-3 (IGFBP3) system are known to be involved in the development of experimental diabetic nephropathy, and urinary IGFBP3 protease activity has been observed in patients with type 2 diabetes. A serine protease was found to be responsible for the proteolytic activity in diabetic urine; however, the identity of the precise enzyme remains unknown. We investigated neutrophil proteinase 3 (PR3) to see whether it has specific enzymatic activity associated with insulin-like growth factor-1 and IGFBP3. In our study, both molecules were sufficiently degraded, which leads us to believe that PR3 may induce insulin resistance in the mouse model utilized. In addition, we found that PR3 in the urine of diabetic patients similarly affects insulin resistance. Moreover, PR3-immunized mice had an increase in glucose clearance due to inhibition of PR3 activity. As such, PR3 can be considered as an inflammatory enzyme directly linking inflammation to type 2 diabetes through downregulation of insulin-like growth factor-1/IGFBP3.

Oxidized von Willebrand factor is efficiently cleaved by serine proteases from primary granules of leukocytes: divergence from ADAMTS-13

BACKGROUND

The leukocyte serine proteases (LSPs) elastase, proteinase 3 and cathepsin G cleave von Willebrand factor (VWF) near or at the same cleavage site (Tyr1605-Met1606) as ADAMTS-13, the metalloprotease that specifically controls the proteolytic processing of VWF. Recent studies have shown that oxidation of VWF at Met1606 with formation of methionine sulfoxide (MetSO) severely impairs its proteolysis by ADAMTS-13.

METHODS

This study was aimed at assessing whether or not oxidation of VWF by reactive oxygen species (ROS) can also affect its cleavage by elastase, proteinase 3, and cathepsin G. In this study, the catalytic specificity of hydrolysis by LSPs of the VWF peptide substrate VWF74 and full-length VWF, both unaltered and in the oxidized form, was measured by RP-HPLC, electrophoretic and mass spectrometry methods.

RESULTS

LSPs cleaved both VWF multimers and VWF74 near or at the same peptide bond as is cleaved by ADAMTS-13, with k(cat)/K(m) values similar to those of the metalloprotease. However, unlike ADAMTS-13, cathepsin G cleaved VWF74 containing a MetSO residue at position 1606 with a k(cat)/K(m) value higher than that for VWF74, whereas the catalytic efficiencies of both elastase and proteinase 3 were unaffected by the replacement of Met1606 with MetSO. Likewise, oxidation of VWF multimers by hypochlorous acid and ROS, produced by activated leukocytes, improved their hydrolysis by LSPs.

CONCLUSIONS

Oxidation by leukocyte ROS has a net positive effect on the cleavage of VWF multimers by LSPs, under conditions where high concentrations of oxidant species would severely reduce the proteolytic efficiency of ADAMTS-13.

Loss of expression of neutrophil proteinase-3: a factor contributing to thrombotic risk in paroxysmal nocturnal hemoglobinuria

BACKGROUND

A deficiency of specific glycosylphosphatidyl inositol-anchored proteins in paroxysmal nocturnal hemoglobinuria may be responsible for most of the clinical features of this disease, but some functional consequences may be indirect. For example, the absence of certain glycosylphosphatidyl inositol-anchored proteins in paroxysmal nocturnal hemoglobinuria cells may influence expression of other membrane proteins. Membrane-bound proteinase 3 co-localizes with glycosylphosphatidyl inositol-linked neutrophil antigen 2a, which is absent in patients with paroxysmal nocturnal hemoglobinuria.

DESIGN AND METHODS

We compared expression of proteinase 3 and neutrophil antigen 2a by flow cytometry and western blotting in normal and paroxysmal nocturnal hemoglobinuria cells and measured cytoplasmic and soluble levels of proteinase 3 by enzyme-linked immunosorbent assays in controls and patients with paroxysmal nocturnal hemoglobinuria. Finally, we studied the effects of proteinase 3 on platelet activation using an in vitro aggregometry assay and flow cytometry.

RESULTS

We showed that membrane-bound proteinase 3 is deficient in patients' cells, but invariantly present in the cytoplasm regardless of disease phenotype. When we isolated lipid rafts from patients, both molecules were detected only in the rafts from normal cells, but not diseased ones. Membrane-bound proteinase 3 was associated with a decrease in plasma proteinase 3 levels, clone size and history of thrombosis. In addition, we found that treating platelets ex vivo with proteinase 3, but not other agonists, decreased the exposure of an epitope on protease activated receptor-1 needed for thrombin activation. Conversely, treatment of whole blood with serine protease inhibitor enhanced expression of this epitope on protease activated receptor-1 located C-terminal to the thrombin cleavage site on platelets.

CONCLUSIONS

We demonstrated that deficiency of glycosylphosphatidyl inositol-anchored proteins in paroxysmal nocturnal hemoglobinuria results in decreased membrane-bound and soluble proteinase 3 levels. This phenomenon may constitute another mechanism contributing to a prothrombotic propensity in patients with paroxysmal nocturnal hemoglobinuria.

Anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis: where to go?

Enormous progress has been made during the last 25 years in our understanding of the aetiopathogenesis of the anti-neutrophil cytoplasmic autoantibody (ANCA)-associated vasculitides (AAV). This has led to improvements in early diagnosis, treatment and secondary prevention of these diseases. Nevertheless, there are still unmet needs in the AAV. With respect to diagnosis and follow-up, sensitive biomarkers that reflect disease activity, also during smouldering disease, are needed. In the field of aetiopathogenesis, genetic and epigenetic studies are being performed not only directed at the autoimmune response but also at the expression of, possibly modified, autoantigens. Environmental factors, in particular microbial factors, are also being explored. This will enable analysis of gene-environment interactions in the AAV, so elucidating further their aetiopathogenesis. Explaining the differences in clinical presentation between proteinase 3 (PR3)-associated AAV and myeloperoxidase (MPO)-associated AAV requires an adequate animal model for PR3-ANCA disease, which is currently lacking. Although many large randomized controlled trials have built a base for a rational therapeutic approach in the AAV, late morbidity and mortality is still significant. The availability of new biologicals and the development of sensitive biomarkers for disease activity could further improve prognosis for patients suffering from AAV.

Complement receptor Mac-1 is an adaptor for NB1 (CD177)-mediated PR3-ANCA neutrophil activation

The glycosylphosphatidylinositol (GPI)-anchored neutrophil-specific receptor NB1 (CD177) presents the autoantigen proteinase 3 (PR3) on the membrane of a neutrophil subset. PR3-ANCA-activated neutrophils participate in small-vessel vasculitis. Since NB1 lacks an intracellular domain, we characterized components of the NB1 signaling complex that are pivotal for neutrophil activation. PR3-ANCA resulted in degranulation and superoxide production in the mNB1(pos)/PR3(high) neutrophils, but not in the mNB1(neg)/PR3(low) subset, whereas MPO-ANCA and fMLP caused similar responses. The NB1 signaling complex that was precipitated from plasma membranes contained the transmembrane receptor Mac-1 (CD11b/CD18) as shown by MS/MS analysis and immunoblotting. NB1 co-precipitation was less for CD11a and not detectable for CD11c. NB1 showed direct protein-protein interactions with both CD11b and CD11a by surface plasmon resonance analysis (SPR). However, when these integrins were presented as heterodimeric transmembrane proteins on transfected cells, only CD11b/CD18 (Mac-1)-transfected cells adhered to immobilized NB1 protein. This adhesion was inhibited by mAb against NB1, CD11b, and CD18. NB1, PR3, and Mac-1 were located within lipid rafts. In addition, confocal microscopy showed the strongest NB1 co-localization with CD11b and CD18 on the neutrophil. Stimulation with NB1-activating mAb triggered degranulation and superoxide production in mNB1(pos)/mPR3(high) neutrophils, and this effect was reduced using blocking antibodies to CD11b. CD11b blockade also inhibited PR3-ANCA-induced neutrophil activation, even when β2-integrin ligand-dependent signals were omitted. We establish the pivotal role of the NB1-Mac-1 receptor interaction for PR3-ANCA-mediated neutrophil activation.

Adoptive transfer of PR1 cytotoxic T lymphocytes associated with reduced leukemia burden in a mouse acute myeloid leukemia xenograft model

BACKGROUND AIMS

Tumor antigen-specific cytotoxic T lymphocytes (CTL) have been used in the treatment of human cancer, including leukemia. Several studies have established PR1 peptide, an HLA-A2.1-restricted peptide derived from proteinase 3 (P3), as a human leukemia-associated antigen. PR1-specific CTL elicited in vitro from healthy donors have been shown to lyse P3-expressing AML cells from patients. We investigated whether PR1-CTL can be adoptively transferred into NOD/SCID mice to eliminate human leukemia cells.

METHODS

PR1-CTL were generated in bulk culture from peripheral blood mononuclear cells (PBMC) stimulated with autologous dendritic cells. Human acute myeloid leukemia (AML) patient samples were injected and engrafted in murine bone marrow at 2 weeks post-transfer.

RESULTS

Following adoptive transfer, bone marrow aspirate from mice that received AML alone had 72-88% blasts in a hypercellular marrow, whereas mice that received AML plus PR1-CTL co-infusion had normal hematopoietic elements and only 3-18% blasts in a hypocellular marrow. The PR1-CTL persisted in the bone marrow and liver and maintained a CD45RA⁻CD28+ effector phenotype.

CONCLUSIONS

We found that adoptive transfer of PR1-CTL generated in vitro is associated with reduced AML cells in NOD/SCID mice. PR1-CTL can migrate to the sites of disease and maintain their capacity to kill the AML cells. The surface phenotype of PR1-CTL was consistent with their trafficking pattern in both vascular and end-organ tissues.

Transcription of proteinase 3 and related myelopoiesis genes in peripheral blood mononuclear cells of patients with active Wegener's granulomatosis

OBJECTIVE

Wegener's granulomatosis (WG) is a systemic inflammatory disease that is associated with substantial morbidity. The aim of this study was to understand the biology underlying WG and to discover markers of disease activity that would be useful for prognosis and treatment guidance.

METHODS

Gene expression profiling was performed using total RNA from peripheral blood mononuclear cells (PBMCs) and granulocyte fractions from 41 patients with WG and 23 healthy control subjects. Gene set enrichment analysis (GSEA) was performed to search for candidate WG-associated molecular pathways and disease activity biomarkers. Principal components analysis was used to visualize relationships between subgroups of WG patients and controls. Longitudinal changes in proteinase 3 (PR3) gene expression were evaluated using reverse transcription-polymerase chain reaction, and clinical outcomes, including remission status and disease activity, were determined using the Birmingham Vasculitis Activity Score for WG (BVAS-WG).

RESULTS

Eighty-six genes in WG PBMCs and 40 in WG polymorphonuclear neutrophils (PMNs) were significantly up-regulated relative to controls. Genes up-regulated in WG PBMCs were involved in myeloid differentiation, and these included the WG autoantigen PR3. The coordinated regulation of myeloid differentiation genes was confirmed by GSEA. The median expression values of the 86 up-regulated genes in WG PBMCs were associated with disease activity (P = 1.3 x 10(-4)), and WG patients with low-level expression of the WG signature genes showed expression profiles that were only modestly different from that in healthy controls (P = 0.07). PR3 transcription was significantly up-regulated in WG PBMCs (P = 1.3 x 10(-5), false discovery rate [FDR] 0.002), but not in WG PMNs (P = 0.03, FDR 0.28), and a preliminary longitudinal analysis showed that the fold change in PR3 RNA levels in WG PBMCs corresponded to changes in the BVAS-WG score over time.

CONCLUSION

Transcription of PR3 and related myeloid differentiation genes in PBMCs may represent novel markers of disease activity in WG.

Membrane proteinase 3 (mPR3) expression on neutrophils is not increased in localized Wegener's granulomatosis (WG) and Churg-Strauss syndrome (CSS)

OBJECTIVES

The aim of this study was to analyse mPR3 expression on neutrophils in two Anti-neutrophil cytoplasm antibody (ANCA)-associated vasculitides (AAV), namely WG (localised vs. generalised) and Churg-Strauss syndrome (CSS) and other inflammatory disorders, in order to evaluate (i) whether the pattern of mPR3 expression is specific for AAV and (ii) to assess whether the mPR3high status is associated with clinically distinct disease stages of WG (localised vs. generalised).

METHODS

Localised WG (n=15), generalised WG (n=55), Churg-Strauss Syndrome (CSS) (n=20), systemic lupus erythematosus (SLE) (n=15), Rheumatoid Arthritis (RA) (n=22) and healthy controls (n=30) were analysed. mPR3 and CD63 expression on surface of neutrophils were assessed by flow cytometric analysis on isolated neutrophils and whole blood.

RESULTS

In patients with genWG and SLE, an increased percentage of mPR3+ neutrophils and an elevated level of mPR3 expression compared to healthy controls were found (percentage: p=0.001, p=0.000; MFI ratio: p=0.038, p=0.019, respectively). There was no increased frequency of mPR3+ neutrophils in CSS. Within the group of WG, an elevated level of mPR3 expression was significantly associated with disease stage (genWG and not locWG), and in genWG with disease activity and the presence of ANCA.

CONCLUSIONS

The mPR3high status is associated with generalised WG and correlates with disease activity and ANCA status in generalised WG. An increased proportion of mPR3-positive neutrophils is not specific for AAV.

The role of proteinase 3 (PR3) and the protease-activated receptor-2 (PAR-2) pathway in dendritic cell (DC) maturation of human-DC-like monocytes and murine DC

OBJECTIVES

The aim of the study was to assess PAR-2 expression on dendritic cell (DC) subsets and other immune cells of Wegener's granulomatosis (WG) patients and healthy controls (HC) and to investigate whether Proteinase 3 (PR3, a serine protease which can activate PAR2) induces maturation of human DC-like monocytes and murine Flt-3 ligand- and GM-CSF-generated DC.

METHODS

Human peripheral blood cells including DC subsets and Flt-3l- and GM-CSF-generated mouse DC were analysed for expression of PAR-2 and DC maturation markers by flow cytometry before and after stimulation with PR3, trypsin, PAR-2 agonist or LPS for 24 h.

RESULTS

There was no difference of PAR-2 expression on PMNs, monocytes, lymphocytes and DC between all WG samples and HC. However, in inactive WG, expression of PAR-2 was downregulated on the cell surface of PMNs, monocytes, lymphocytes, and CD11c+DC compared to active WG and HC. PR3 and PAR2-agonists did not induce upregulation of PAR-2 or maturation markers of human DC-like monocytes in WG and HC. Likewise, murine PR3 did not induce upregulation of PAR-2 or maturation markers in murine DC.

CONCLUSIONS

PAR-2 expression is downregulated on human peripheral blood cells including CD11c+ DC in inactive WG compared to active WG and HC, possibly reflecting a non-activated status of these cells in inactive disease. PR3 and PAR-2- agonists did not induce maturation of human ex vivo DC-like monocytes in WG and HC and of murine DC, suggesting this pathway is not singularly involved in the maturation of these cell subsets.

Inflammatory arthritis in caspase 1 gene-deficient mice: contribution of proteinase 3 to caspase 1-independent production of bioactive interleukin-1beta

OBJECTIVE

Caspase 1, a known cysteine protease, is a critical component of the inflammasome. Both caspase 1 and neutrophil serine proteases such as proteinase 3 (PR3) can process pro-interleukin-1beta (proIL-1beta), a crucial cytokine linked to the pathogenesis of rheumatoid arthritis. This study was undertaken to establish the relative importance of caspase 1 and serine proteases in mouse models of acute and chronic inflammatory arthritis.

METHODS

Acute and chronic arthritis were induced in caspase 1-/- mice, and the lack of caspase 1 was investigated for its effects on joint swelling, cartilage metabolism, and histopathologic features. In addition, caspase 1 activity was inhibited in mice lacking active cysteine proteases, and the effects of dual blockade of caspase 1 and serine proteases on arthritis severity and histopathologic features were evaluated.

RESULTS

Surprisingly, caspase 1-/- mice, in a model of acute (neutrophil-dominated) arthritis, developed joint swelling to an extent similar to that in wild-type control mice. Joint fluid concentrations of bioactive IL-1beta were comparable in caspase 1-/- mice and controls. In contrast, induction of chronic arthritis (characterized by minimal numbers of neutrophils) in caspase 1-/- mice led to reduced joint inflammation and less cartilage damage, implying a caspase 1-dependent role in this process. In mice lacking neutrophil serine PR3, inhibition of caspase 1 activity resulted in decreased bioactive IL-1beta concentrations in the synovial tissue and less suppression of chondrocyte anabolic function. In addition, dual blockade of both PR3 and caspase 1 led to protection against cartilage and bone destruction.

CONCLUSION

Caspase 1 deficiency does not affect neutrophil-dominated joint inflammation, whereas in chronic arthritis, the lack of caspase 1 results in reduced joint inflammation and cartilage destruction. These findings suggest that inhibitors of caspase 1 are not able to interfere with the whole spectrum of IL-1beta production, and therefore such inhibitors may be of therapeutic value only in inflammatory conditions in which limited numbers of neutrophils are present.

Mechanism-based inhibitors of serine proteases with high selectivity through optimization of S' subsite binding

A series of mechanism-based inhibitors designed to interact with the S' subsites of serine proteases was synthesized and their inhibitory activity toward the closely-related serine proteases human neutrophil elastase (HNE) and proteinase 3 (PR 3) was investigated. The compounds were found to be time-dependent inhibitors of HNE and were devoid of any inhibitory activity toward PR 3. The results suggest that highly selective inhibitors of serine proteases whose primary substrate specificity and active sites are similar can be identified by exploiting differences in their S' subsites. The best inhibitor (compound 16) had a k(inact)/K(I) value of 4580 M(-1)s(-1).

Glycosylation of proteinase 3 (PR3) is not required for its reactivity with antineutrophil cytoplasmic antibodies (ANCA) in Wegener's granulomatosis

OBJECTIVE

The glycosylation status of autoantigens appears to be crucial for the pathogenesis of some autoimmune diseases, since carbohydrates play a crucial role in the distinction of self from non-self. Proteinase 3 (PR3), the main target antigen for anti-neutrophil cytoplasmic antibodies (ANCA) in patients with Wegener's granulomatosis (WG), contains two Asn-linked glycosylation sites. The present study explores the influence of the glycosylation status of PR3 on the PR3 recognition by ANCA in a well characterized population of patients with WG.

METHODS

Forty-four patients with WG (459 serum samples) who participated in a multicenter randomized trial, were tested by capture ELISA for ANCA against PR3 and deglycosylated recombinant variants of PR3.

RESULTS

The patients were followed for a median of 27 months, and the median number of serum samples per patient was 10. At baseline, the correlation between the levels of ANCA against PR3 and against all the deglycosylated recombinant variants of PR3 were greater than 0.94 (?<0.001 for all the comparisons). Longitudinal analyses comparing the levels of ANCA against PR3 versus all the deglycosylated recombinant variants of PR3, using linear mixed models, showed no significant statistical differences (rho >or=0.90 in all cases).

CONCLUSION

The glycosylation status of PR3 has no impact on its recognition by ANCA in WG.

Modulation of tissue factor and tissue factor pathway inhibitor-1 by neutrophil proteases

During systemic inflammation, neutrophil activation is accompanied by endothelial cell damage and hypercoagulability. Activated neutrophils release serine proteases that participate in tissue injury. We sought to investigate the effects of neutrophil proteases on proinflammatory and procoagulant changes in endothelial cells. The effects of elastase (HNE), cathepsin G (CG), and proteinase 3 (PR3) on expression of tissue factor (TF) and tissue factor pathway inhibitor-1 (TFPI) were examined in human umbilical vein endothelial cells. Flow cytometry demonstrated that these proteases proteolytically degraded endothelial cell-bound TFPI. TFPI mRNA expression was reduced by HNE and CG. PR3, but not HNE or CG, increased surface expression of TF and TF mRNA. Yet, increased TF expression did not enhance TF activity suggesting induction of encrypted TF. Using antibodies and siRNA to inhibit and silence PAR-1 and PAR-2, we observed that PR3 upregulation of TF is at least in part mediated by PAR-1. Although CG and HNE cleaved PAR-1, antibody reactivity to the PAR-1 hirudin-like sequence demonstrated inactivating cleavage, accounting for the selective ability of PR3 to induce PAR-1-mediated procoagulant effects. This was supported by induction of p42/44 MAPK by PR3. In conclusion, PR3 degradation of TFPI increases the procoagulant activity of endothelial cells. Release of PR3 after neutrophil activation may represent an important step in neutrophil-mediated vascular injury.

Neutrophil elastase cleaves laminin-332 (laminin-5) generating peptides that are chemotactic for neutrophils

Proteolytic processing of laminin-332 by matrix metalloproteinase (MMP)-2 and MMP-14 has been shown to yield fragments that are promigratory for epithelial cells. During acute and chronic inflammation, proteases are elaborated by neutrophils and macrophages that can degrade basement membranes. We investigated the susceptibility of laminin-332 to degradation by the following neutrophil and macrophage proteases: neutrophil elastase (NE), cathepsin G, proteinase-3, and MMPs-2, -8, -9, and -12. Protease-specific differences were seen in the capacity to cleave the individual chains of laminin-332. NE and MMP-12 showed the greatest activity toward the gamma2 chain, generating a fragment similar in size to the gamma2x fragment generated by MMP-2. The digestion pattern of laminin-332 by degranulated neutrophils was nearly identical to that generated with NE alone. Digestion by supernatants of degranulated neutrophils was blocked by an inhibitor of NE, and NE-deficient neutrophils were essentially unable to digest laminin-332, suggesting that NE is the major neutrophil-derived protease that degrades laminin-332. In vivo, laminin gamma2 fragments were found in the bronchoalveolar lavage fluid of wild-type mice treated with lipopolysaccharide, whereas that obtained from NE-deficient mice showed a different cleavage pattern. In addition, NE cleaved a synthetic peptide derived from the region of human laminin gamma2 containing the MMP-2 cleavage site, suggesting that NE may generate laminin-332 fragments that are also promigratory. Both laminin-332 fragments generated by NE digestion and NE-digested laminin gamma2 peptide were found to be chemotactic for neutrophils. Collectively, these data suggest that degradation of laminin-332 by NE generates fragments with important biological activities.

Design of selective substrates of proteinase 3 using combinatorial chemistry methods

In this study, chemical synthesis of the selective chromogenic/fluorogenic substrates for proteinase 3 is described. The substrates' sequence was obtained using combinatorial chemistry methods. Deconvolution of the tripeptide library against proteinase 3 with general formula ABZ-X3-X2-X1-ANB-NH2 yielded the active sequence. Selected peptide was further modified on its C terminus to investigate the impact of chromophore moiety modification on enzyme-substrate interaction. To determine specificity, activity of selected substrates was characterized against proteinase 3 and neutrophil elastase. Finally, the peptide ABZ-Tyr-Tyr-Abu-ANB-NH2 displayed the highest value of specificity constant (k(cat)/K(M)=189 x 10(3) M(-1) s(-1)) for proteinase 3. To the best of our knowledge, this is the first short peptide that undergoes selective proteolysis by proteinase 3 and displays no significant hydrolysis in the presence of human neutrophil elastase and cathepsin G.

T cells in the pathogenesis of ANCA-associated vasculitis: current knowledge

AAV are a group of systemic immune-mediated diseases with a strong and highly specific association with ANCA. In recent years, there has been increasing evidence that ANCA might play a direct pathogenic role in triggering AAV. Nevertheless, effectors of cell-mediated immunity prevail in the inflammation sites in patients with AAV. Numerous studies found increased markers of T-cell activation in AAV. Moreover, this activation persisted even in remission and despite treatment. Finally, successful therapeutic attempts using T cell-directed treatment were also reported. There has therefore been substantial evidence that T cells are involved in the pathogenesis of AAV, even though the exact mechanisms are yet to be elucidated. In this review, recent findings on the contribution of T cells to the pathogenic processes in AAV will be briefly summarized. Special emphasis will be placed on the Th1/Th2 concept, the role of T-regulatory cells, and the role of effector memory T cells in the pathogenesis of AAV.

A case of proteinase 3-antineutrophil cytoplasmic antibody-positive Sjögren's syndrome complicated with interstitial nephritis

A 65-year-old woman who had fever was admitted. Laboratory data showed renal tubular dysfunction, elevated C-reactive protein, soluble interleukin-2 receptor (sIL-2R), and IgG. Her blood showed proteinase 3-antineutrophil cytoplasmic antibody (PR3-ANCA) as well as antinuclear antibody and anti-Ro/SS-A antibody. Salivary gland and renal biopsy showed inflammatory infiltration of lymphocytes. A diagnosis of Sjögren's syndrome (SS) and interstitial nephritis was made. beta(2)-microglobulin, sIL-2R, IgG, and PR3-ANCA were decreased in response to medium-dose oral prednisolone. Antineutrophil cytoplasmic antibody could be a new marker for extraglandular features of SS. It would be beneficial for SS patients who have positive ANCA to investigate extraglandular lesions such as interstitial nephritis.

Proteinase 3, the Wegener autoantigen, is externalized during neutrophil apoptosis: evidence for a functional association with phospholipid scramblase 1 and interference with macrophage phagocytosis

Proteinase 3 (PR3), a serine proteinase contained in neutrophil azurophilic granules, is considered a risk factor for vasculitides and rheumatoid arthritis when expressed on the outer leaflet of neutrophil plasma membrane and is the preferred target of antineutrophil cytoplasm autoantibodies (ANCA) in Wegener granulomatosis. ANCA binding to PR3 expressed at the surface of neutrophils activates them. Evidence is provided that neutrophil apoptosis induced significantly more membrane PR3 expression without degranulation (but no enhanced membrane CD35, CD66b, CD63, myeloperoxidase, or elastase expression). This observation was confirmed on cytoplasts, a model of granule-free neutrophils. We hypothesized that PR3 could interact with proteins involved in membrane flip-flop (eg, phospholipid scramblase 1 [PLSCR1]). PR3-PLSCR1 interaction in neutrophils was demonstrated by confocal microscopy and coimmunoprecipitation. In the RBL-2H3 rat mast-cell line stably transfected with PR3 or its inactive mutant (PR3S203A), PR3 externalization depended on PLSCR1, as shown by less PR3 externalization in the presence of rPLSCR1 siRNA, but independently of its serine-proteinase activity. Finally, apoptosis-externalized PR3 decreased the human macrophage-phagocytosis rate of apoptotic PR3 transfectants. Therefore, in addition to ANCA binding in vasculitis, the proinflammatory role of membrane PR3 expression may involve interference with macrophage clearance of apoptotic neutrophils.

Apoptosis of human neutrophils induced by protein phosphatase 1/2A inhibition is caspase-independent and serine protease-dependent

Protein phosphatase (PP) activity is associated with the regulation of apoptosis in neutrophils. However, the underlying regulatory mechanism(s) in apoptosis remain unclear. The type of cell death induced by okadaic acid (OA), the inhibitor of PP1 and PP2A, is characterized by apoptotic morphological changes of the cells and annexin V-positive staining without DNA fragmentation. The apoptotic effects of OA and calyculin A on neutrophils were observed at concentrations ranging from 50 to 200 nM, or 10 to 50 nM, respectively. Cyclosporine A (a PP2B specific inhibitor), however, did not exhibit any pro-apoptotic effects. OA and calyculin A, but not cyclosporine A, exhibited significant effects on protein levels and on the electrophoretic mobility of Mcl-1. zVAD-fmk, a pancaspase inhibitor, failed to inhibit the effect of OA on the caspase-3 activity, procaspase-3 processing, and the apoptotic rate of neutrophils. However, 4-(2-aminoethyl) benzenesulfonylfluoride (AEBSF), a general serine protease inhibitor, significantly abrogated the OA-induced mobility shift in procaspase-3, caspase-3 activation, and the apoptotic morphological changes in neutrophils. Moreover, OA enhanced the serine protease activity of the neutrophils. The addition of the proteinase-3 protein increased the rate of neutrophil apoptosis, which was also blocked by AEBSF but not by zVAD-fmk. These results suggest that OA induces procaspase-3 processing but that OA-induced apoptosis is caspase-independent and serine protease-dependent.

Annexin 1 cleavage in activated neutrophils: a pivotal role for proteinase 3

Annexin 1 is an anti-inflammatory protein that plays a key role in innate immunity by modulating the activation of several types of cells, including neutrophils. Here we have developed a cleavage assay using tagged annexin 1 and observed marked activity in the membrane fraction of activated neutrophils. A combination of inhibitors, transfected cells, and proteomic analyses allowed us to identify proteinase 3 as the main enzyme responsible for this cleavage in the N terminus region of the protein, at least in the context of neutrophil activation. Because annexin 1 is an important endogenous anti-inflammatory mediator, blocking its cleavage by proteinase 3 would augment its homeostatic pro-resolving actions and could represent an opportunity for innovative anti-inflammatory drug discovery.