Structure of the azurocidin, proteinase 3, and neutrophil elastase genes. Implications for inflammation and vasculitis

Mechanisms of neutrophil extracellular trap in chronic inflammation of endothelium in atherosclerosis

Cardiovascular diseases are a primary cause of morbidity and mortality around the world. In addition, atherosclerosis (AS)-caused cardiovascular disease is the primary cause of death in human diseases, and almost two billion people suffer from carotid AS worldwide. AS is caused by chronic inflammation of the arterial vessel and is initiated by dysfunction of vascular endothelial cells. Neutrophils protect against pathogen invasion because they function as a component of the innate immune system. However, the contribution of neutrophils to cardiovascular disease has not yet been clarified. Neutrophil extracellular traps (NETs) represent an immune defense mechanism that is different from direct pathogen phagocytosis. NETs are extracellular web-like structures activated by neutrophils, and they play important roles in promoting endothelial inflammation via direct or indirect pathways. NETs consist of DNA, histones, myeloperoxidase, matrix metalloproteinases, proteinase 3, etc. Most of the components of NETs have no direct toxic effect on endothelial cells, such as DNA, but they can damage endothelial cells indirectly. In addition, NETs play a critical role in the process of AS; therefore, it is important to clarify the mechanisms of NETs in AS because NETs are a new potential therapeutic target AS. This review summarizes the possible mechanisms of NETs in AS.

Bioinformatic analysis identifies potential key genes of epilepsy

Background

Epilepsy is one of the most common brain disorders worldwide. It is usually hard to be identified properly, and a third of patients are drug-resistant. Genes related to the progression and prognosis of epilepsy are particularly needed to be identified.

Methods

In our study, we downloaded the Gene Expression Omnibus (GEO) microarray expression profiling dataset GSE143272. Differentially expressed genes (DEGs) with a fold change (FC) >1.2 and a P-value <0.05 were identified by GEO2R and grouped in male, female and overlapping DEGs. Functional enrichment analysis and Protein-Protein Interaction (PPI) network analysis were performed.

Results

In total, 183 DEGs overlapped (77 ups and 106 downs), 302 DEGs (185 ups and 117 downs) in the male dataset, and 750 DEGs (464 ups and 286 downs) in the female dataset were obtained from the GSE143272 dataset. These DEGs were markedly enriched under various Gene Ontology (GO) terms and Kyoto Encyclopedia of Genes and Genomes (KEGG) terms. 16 following hub genes were identified based on PPI network analysis: ADCY7, C3AR1, DEGS1, CXCL1 in male-specific DEGs, TOLLIP, ORM1, ELANE, QPCT in female-specific DEGs and FCAR, CD3G, CLEC12A, MOSPD2, CD3D, ALDH3B1, GPR97, PLAUR in overlapping DEGs.

Conclusion

This discovery-driven study may be useful to provide a novel insight into the diagnosis and treatment of epilepsy. However, more experiments are needed in the future to study the functional roles of these genes in epilepsy.

Heparin-binding protein and procalcitonin in the diagnosis of pathogens causing community-acquired pneumonia in adult patients: a retrospective study

The performance of inflammatory markers in community-acquired pneumonia (CAP) caused by different pathogens has not been fully studied. We sought to find the differences in the concentrations of procalcitonin (PCT) and heparin-binding protein (HBP) between patients with CAP caused by different pathogens. We enrolled 162 patients with CAP, divided into three groups on the basis of bacterial (n = 108), fungal (n = 21) and viral (n = 33) infection. Complete leukocyte counts and the concentration of HBP and PCT were measured, and the differences were compared with nonparametric tests. The receiver operating characteristic (ROC) curve was used to evaluate the significant differences in the sensitivity and specificity of the indicators. The leukocyte and neutrophils counts and the concentrations of HBP and PCT in the viral group were significantly lower than those in the other two groups (p < 0.001). The area under the ROC curve (AUC) of the concentration of HBP and PCT as well as leukocyte and neutrophils counts were 0.927, 0.892, 0.832 and 0.806 for distinguishing bacterial from viral infection, respectively. The best cut-off value was 20.05 ng/mL for HBP, with a sensitivity of 0.861 and specificity of 0.939. The best cut-off value was 0.195 ng/mL for PCT, with a sensitivity of 0.991 and specificity of 0.636. The best cut-off value was 5.195 × 10⁹/L and 4.000 × 10⁹/L for leukocyte and neutrophils counts, with sensitivity of 0.694 and 0.880 and specificity of 0.667 and 0.636, respectively. The AUC of HBP, PCT and leukocyte and neutrophil counts for distinguishing fungal from viral infection were 0.851, 0.883, 0.835 and 0.830, respectively. The best cut-off values were 29.950 ng/mL, 0.560 ng/mL, 5.265 × 10⁹/L and 3.850 × 10⁹/L, with sensitivity of 0.667, 0.714, 0.905 and 0.952 and specificity of 0.970, 0.879 0.667 and 0.606, respectively. There were no significant differences in the three indicators between the bacterial and fungal infection groups. The concentration of CRP showed no significant differences among the three groups. Consequently, the stronger immune response characterized by higher inflammation markers including HBP and PCT can help distinguish bacterial and fungal CAP from viral CAP.

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.

The diagnostic role and clinical association of serum proteinase 3 anti-neutrophil cytoplasmic antibodies in Chinese patients with inflammatory bowel disease

Background and aim: Accurate differentiation of patients with ulcerative colitis (UC) or Crohn's disease (CD) is important for appropriate therapy and prognosis. This study was designed to explore the utility of proteinase 3 anti-neutrophil cytoplasmic antibodies (PR3-ANCA) in the diagnosis of Chinese patients with inflammatory bowel disease (IBD).Methods: Blood samples were collected from 216 Chinese patients, including 175 IBD and 41 colorectal polyps (disease control). Clinical characteristics were extracted from electronic medical records.Results: Serum PR3-ANCA were increased in UC patients compared to those with CD or colorectal polyps (p < .0001). PR3-ANCA was negative in colorectal polyps and there was no significant difference between CD and colorectal polyps (p > .05). Using the cut-off value of 20 chemiluminescent units (CU) provided by manufacturer, the positive rate of PR3-ANCA was higher in UC than CD (41.7% vs. 1.1%; p < .0001). Receiver operating characteristic (ROC) analysis demonstrated an area under the curve (AUC) of 0.89 (95% CI: 0.84-0.95; p < .0001) for differentiating UC from CD and suggested an optimized cutoff of 7.3 CU which improved sensitivity from 41.7% to 57.1%, while maintaining a specificity of 98.9%. PR3-ANCA in severe UC patients were higher than those with moderate UC (p < .05), no difference was found between those in remission or with mild or moderate activity (p > .05).Conclusions: Serum PR3-ANCA is a potentially useful clinical biomarker in Chinese patients with IBD. A modified cut-off value of 7.3 CU improves the performance for distinguishing UC from CD.

A DNA-Methylated Sight on Autoimmune Inflammation Network across RA, pSS, and SLE

Methylation variabilities of inflammatory cytokines play important roles in the development of systemic lupus erythematosus (SLE), rheumatoid arthritis (RA), and primary Sjögren's syndrome (pSS). With heightened focus on personalized and precise medicine, it is necessary to compare and contrast the difference and similarity of cytokine methylation status between the 3 most classic autoimmune diseases (AIDs). In this study, we integrated 5 Cytokine-Chips from genome-wide DNA methylation datasets of the 3 kind of AIDs, delta-beta value was calculated for intergroup difference, and comprehensive bioinformatics analyses of cytokine genes with aberrant methylations were performed. 125 shared differential methylation variabilities (DMVs) were identified. There were 102 shared DMVs with similar methylation status; 3 hypomethylated differential methylation regions (DMRs) across the AIDs were found, and all 3 DMRs were hypomethylated. DMRs (AZU1, LTBR, and RTEL1) were likely to serve as activator in the inflammatory process. Particularly, AZU1 and LTBR with hypomethylated TSS and first exon located in the promoter regions were able to trigger inflammation signaling cascades and play critical roles in autoimmune tautology. Moreover, functional epigenetic module (FEM) algorithm showed that different inflammatory networks are involved in different AIDs; 5 hotspots were identified as biologically plausible pathways in inducing or perpetuating of inflammation which are epigenetically deregulated in AIDs. We concluded methylation variabilities among the same cytokines can greatly impact the perpetuation of inflammatory process or signal pathway of AIDs. Differentiating the cytokine methylation status will serve as valuable resource for researchers alike to gain better understanding of the epigenetic mechanisms of the three AIDs. Even more importantly, better understanding of cytokine methylation variability existing between the three classic AIDs will aid in identification of potential epigenetic biomarkers and therapeutic targets. This trial is registered with ChiCTR-INR-16010290, a clinical trial for the treatment of rheumatoid arthritis with Warming yang and Smoothening Meridians.

Gingival Tissue and Crevicular Fluid Co-operation in Adult Periodontitis

Activated matrix metalloproteinase-3 (MMP-3) can contribute to periodontal ligament destruction in adult periodontitis. Since MMP-3 has been reported to activate proMMP-8 and -9, it was speculated that gingival tissue fibroblast-derived MMP-3 might, in periodontitis, be responsible for activation of gingival crevicular fluid (GCF) neutrophil-derived proMMP-8 and -9. Immunohistochemistry disclosed MMP-3 in gingival fibroblasts in periodontitis. Cultured gingival fibroblasts released only pro-MMP-3 when stimulated with tumor necrosis factor-α. However, Western blot revealed partially activated MMP-3, MMP-8, and MMP-9 in periodontitis GCF. Active MMP-8 (p < 0.05) and MMP-9 (p < 0.05) correlated with the presence of active MMP-3. It seems that resident gingival fibroblasts produce pro-MMP-3 in GCF, where it becomes activated, probably by cathepsin G or elastase released by neutrophils. Active MMP-3 then activates neutrophil-derived pro-MMP-8 and -9. Different tissue compartments/cells exert co-operative actions in mutual local MMP activation cascades.

Utility of immunologic testing in suspected rheumatologic disease

The use of diagnostic testing in the clinical practice of medicine has been a shifting landscape from the time that the first blood test was utilized. This is no different in the field of immunology and in particular rheumatology. As the field of immunology is relatively young, the clinical tests are not well established and therefore guidelines for use are still under debate. In this review, we seek to look at some of the key autoantibodies, as well as other tests that are available to diagnose suspected rheumatologic disease, and examine how to best use these tests in the clinic. In particular, we will focus on the anti-nuclear antibodies, anti-neutrophil cytoplasmic antibodies, complement, cryoglobulins, rheumatoid factor, and anti-citrullinated protein antibodies.

Role of Proteases in Inflammatory Lung Diseases

Proteases are enzymes that have the capacity to hydrolyze peptide bonds and degrade other proteins. Proteases can promote inflammation by regulating expression and activity of different pro-inflammatory cytokines, chemokines and other immune components in the lung compartment. They are categorized in three major subcategories: serine proteases, metalloproteases and cysteine proteases especially in case of lung diseases. Neutrophil-derived serine proteases (NSPs), metalloproteases and some mast cell-derived proteases are mainly focused here. Their modes of actions are different in different diseases for e.g. NE induces the release of IL-8 from lung epithelial cells through a MyD88/IRAK/TRAF-6-dependent pathway and also through EGFR MAPK pathway. NSPs contribute to immune regulation during inflammation through the cleavage and activation of specific cellular receptors. MMPs can also influence the progression of various inflammatory processes and there are many non-matrix substrates for MMPs, such as chemokines, growth factors and receptors. During lung inflammation interplay between NE and MMP is an important significant phenomenon. They have been evaluated as therapeutic targets in several inflammatory lung diseases. Here we review the role of proteases in various lung inflammatory diseases with emphasis on their mode of action and contribution to immune regulation during inflammation.

NSP4, an elastase-related protease in human neutrophils with arginine specificity

Neutrophil serine proteases (NSPs) in cytoplasmic granules of neutrophils are regarded as important antimicrobial defense weapons after engulfment and exposure of pathogens to the content of primary granules. Despite intensive studies on neutrophils during the last three decades, only three active serine proteases, neutrophil elastase (NE), cathepsin G (CG), and proteinase 3 (PR3) have been identified in these short-lived cells. Here, we report on the identification of a fourth serine protease (NSP4) with 39% identity to NE and PR3, but arginine specificity, yet sharing features like propeptide processing by dipeptidyl peptidase I, storage, and release as an active enzyme with the three active proteases. We established monoclonal antibodies against NSP4, excluded cross-reactivity to human granzymes, NE, CG, PR3, and azurocidin, and screened for NSP4 protein expression in various human tissues and blood leukocyte populations. Only granulocyte precursors and neutrophil populations from peripheral blood were positive. The content of NSP4 in neutrophil lysates, however, was about 20-fold lower compared with CG. Upon neutrophil activation, NSP4 was released into the supernatant. Profiling its specificity with peptide libraries from Escherichia coli revealed a preference for arginine in P1; it cleaved Tyr-Arg-Phe-Arg-AMC and Ala-Pro-Nva-thiobenzyl esters. NSP4 was inhibited by α(1)-proteinase inhibitor (α(1)-antitrypsin), C1 inhibitor, and most efficiently by antithrombin-heparin, but not by elafin, secretory leukocyte protease inhibitor, α(1)-antichymotrypsin, and monocyte-neutrophil elastase inhibitor. Functional specialization and preferred natural substrates of NSP4 remain to be determined to understand the biological interplay of all four NSPs during neutrophil responses.

Cleavage of the CD11b extracellular domain by the leukocyte serprocidins is critical for neutrophil detachment during chemotaxis

The β(2)-integrin CD11b/CD18 mediates the firm adhesion of neutrophils (PMNs) to epithelial monolayers, a key step in PMN transepithelial migration. To complete the transmigration process, adherent PMNs must detach from epithelial monolayer surfaces to move forward. The mechanism that governs the detachment of adherent PMNs, however, is not clear. Here, we present evidence that cleavage of the CD11b extracellular domain containing the ligand-binding I-domain by 3 structural and functional related serine proteases (elastase, proteinase-3 and cathepsin G) serves as a novel mechanism for PMN detachment after the initial cell adhesion. Kinetic studies showed that the cleavage of CD11b is positively correlated with PMN detachment and subsequent transmigration. Moreover, the results demonstrated that elastase, proteinase-3 and cathepsin G all cleaved the purified, functionally active form of CD11b in a pattern similar to the CD11b shedding that occurs during PMN transmigration. Their cleavage sites on purified CD11b were located at (761)Thr-Ala(762) (elastase/proteinase-3) and (760)Phe-Thr(761) (cathepsin G), respectively. CD11b cleavage and PMN detachment and chemotaxis, were impaired in elastase/cathepsin G-deficient Beige mice; this defect could be restored by the addition of extracellular elastase. By illustrating CD11b shedding by elastase, proteinase-3 and cathepsin G as a novel mechanism for PMN detachment, our study provides novel therapeutic targets for controlling inflammation.

In vivo efficacy of sivelestat in combination with pazufloxacin against Legionella pneumonia

It is important to regulate excessive inflammation when patients with severe infectious disease are treated. Sivelestat sodium hydrate (sivelestat), a neutrophil elastase inhibitor, is used in the treatment of lung injury but its effect on bacterial pneumonia is unknown. The authors examined the efficacy of sivelestat in combination with a fluoroquinolone in a Legionella pneumophila pneumonia mouse model. The combination therapy did not show a significant survival improvement compared to the treatment with fluoroquinolone alone, but reduced bacteria number and inflammatory cells in the early phase. The combination therapy can contribute to treatment of L. pneumophila pneumonia with protecting lungs.

Clinical and pathophysiological significance of anti-neutrophil cytoplasmic autoantibodies in vasculitis syndromes

Necrotizing vasculitis of small blood vessels is a rare condition, but when it affects important organs it can lead to life-threatening organ damage and death. Thus, recognizing these conditions at an early stage before they spread to become systemic is a constant challenge to clinical medicine. The objectives of this review are: to give advice on clinical indications for ANCA diagnostics and laboratory procedures for highly specifically detecting the most important ANCA; to provide some data on the autoantigens involved in ANCA reactivity in small vessel vasculitides; and to discuss at the occurrence of ANCA in different vasculitic populations and at different stages of disease. One important task for the near future will be to standardize the assays used for ANCA detection/quantification and to harmonize the results given to clinicians by ensuring that international reference reagents are used by laboratories and the diagnostic industry. Finally, the author has attempted to summarize the role that ANCA are currently believed to play in the immuno-inflammatory events that take place in tissues and that affect small vessels in idiopathic vasculitis. The review concludes that the presence of ANCA is likely to become an important criterion for diagnosing idiopathic small vessel vasculitis.

A case of cocaine-induced panhypopituitarism with human neutrophil elastase-specific anti-neutrophil cytoplasmic antibodies

OBJECTIVE

To describe a patient with cocaine-induced panhypopituitarism associated with human neutrophil elastase-anti-neutrophil cytoplasmic antibodies (HNE-ANCA).

CASE

A 41-year-old man presented with extreme fatigue, cold intolerance and anorexia with 20 kg weight loss in the last 6 months. His medical history was unremarkable. He snorted cocaine twice a week during the last 6 years. On examination, we saw a pale and skinny man, with a normal blood pressure. Because of the severity of symptoms central hypothyroidism was suspected and very low values of TSH, free thyroxine and free triiodothyronine were measured. His FSH, LH, ACTH, cortisol, prolactin and testosterone levels were also low. Magnetic resonance imaging and computed tomography scan showed a normal-sized pituitary gland entirely embedded in a dense, oedematous, contrast-enhancing mass, and a total destruction of the nasal septum with the absence of conchae and severely impaired sinus walls. A transnasal biopsy showed an acute necrotising, non-specific and non-granulomatous inflammation. Although cocaine-induced panhypopituitarism was suspected, Wegener's granulomatosis could not be excluded. Serology on ANCA showed a strongly positive C-ANCA titre (320 U/l) with specificity for HNE. A cocaine-induced HNE-ANCA-associated panhypopituitarism was diagnosed. Our patient was advised to quit using cocaine immediately and was initially treated with glucocorticoids and testosterone, followed by thyroxine. This led to a dramatic clinical response with an increase of appetite, weight gain and regained energy. After 2 years, the patient is well and his ANCA titre is no longer positive.

CONCLUSION

We describe the first documented case of cocaine-induced panhypopituitarism associated with HNE-specific ANCA.

Chemotactically active proteins of neutrophils

Polymorphonuclear leukocytes (neutrophils) are the first cells that arrive at sites of infection or injury. There, besides their microorganism-targeted effector functions, activated neutrophils secrete numerous chemoattractants that recruit other leukocyte subtypes into the inflamed tissue. First, neutrophil activation leads to the upregulation of the gene expression of several classical chemokines of the CXC and CC families. Second, neutrophil granules contain preformed intracellular storage pools of chemotactically active proteins that are rapidly released upon neutrophil degranulation. The third pathway of generation of chemotactically active proteins by activated neutrophils--shedding and concomitant proteolytic processing of a membrane protein--has recently been demonstrated in our laboratory. In this review, we summarize the essential features of chemoattractant production by neutrophils and their contribution to orchestrating the recruitment of leukocyte subtypes during inflammatory response.

Targeting neutrophil elastase in cystic fibrosis

BACKGROUND

Cystic fibrosis (CF) is a lethal hereditary disease characterised by neutrophil-dominated lung inflammation. These abundant neutrophils produce neutrophil elastase (NE), a destructive serine protease that has direct actions on extracellular matrix proteins and has a role in the host response to inflammation and infection.

OBJECTIVE

This review examines the prospect of developing novel therapies for CF by targeting NE. The authors explore the functions of NE and of naturally-occurring and synthetic NE inhibitors.

METHODS

A literature search was conducted exploring the functions of NE and inhibitors of NE; naturally occurring and synthetic.

CONCLUSIONS

Targeting NE in CF offers therapeutic potential, but optimal inhibitors that can be delivered safely and effectively to the lung are still under development.

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.

Differences between human proteinase 3 and neutrophil elastase and their murine homologues are relevant for murine model experiments

Direct comparisons of human (h) and murine (m) neutrophil elastase (NE) and proteinase 3 (PR3) are important for the understanding and interpretation of inflammatory and PR3-related autoimmune processes investigated in wild-type-, mNE- and mPR3/mNE knockout mice. To this end, we purified recombinant mPR3 and mNE expressed in HMC1 and 293 cells and compared their biophysical properties, proteolytic activities and susceptibility to inhibitors with those of their human homologues, hPR3 and hNE. Significant species differences in physico-chemical properties, substrate specificities and enzyme kinetics towards synthetic peptide substrates, oxidized insulin B chain, and fibrinogen were detected. MeOSuc-AAPV-pNA and Suc-AAPV-pNA were hydrolyzed more efficiently by mPR3 than hPR3, but enzymatic activities of mNE and hNE were very similar. Fibrinogen was cleaved much more efficiently by mPR3 than by hPR3. All four proteases were inhibited by alpha(1)-antitrypsin and elafin. Eglin C inihibited mNE, hNE, mPR3, but not hPR3. SLPI inhibited both NEs, but neither PR3. The custom-designed hNE inhibitor, Val(15)-aprotinin, is a poor inhibitor for mNE. In conclusion, appropriate interpretation of experiments in murine models requires individual species-specific assessment of neutrophil protease function and inhibition.

Antineutrophil cytoplasmic antibodies reacting with human neutrophil elastase as a diagnostic marker for cocaine-induced midline destructive lesions but not autoimmune vasculitis

OBJECTIVE

Human neutrophil elastase (HNE) and proteinase 3 (PR3) are structurally and functionally related. PR3 is the prominent target antigen for antineutrophil cytoplasmic antibodies (ANCAs) in Wegener's granulomatosis (WG). Reported frequencies of HNE ANCAs in WG and other autoimmune diseases range from 0% to 20%. We previously detected HNE ANCAs in patients with cocaine-induced midline destructive lesions (CIMDL). We tested the hypothesis that discrepancies in the reported frequencies of HNE ANCAs in patients with vasculitis may be related to differences in detection methods, and that HNE ANCA may be a marker for CIMDL.

METHODS

HNE ANCA reactivity in 25 patients with CIMDL was characterized and compared with that in a control cohort of 604 consecutive patients (64 with WG, 14 with microscopic polyangiitis [MPA], and 526 others) and 45 healthy volunteers. HNE ANCAs were measured by indirect immunofluorescence using a previously undescribed expression system for recombinant HNE and by direct and capture enzyme-linked immunosorbent assays using purified native HNE as target antigen.

RESULTS

Among patients with CIMDL, HNE ANCAs were detectable by 1 assay in 84%, by 2 assays in 68%, and by all 3 assays in 36%. Fifty-seven percent of HNE ANCA-positive CIMDL sera were also PR3 ANCA-positive by at least 1 assay. In contrast, only 8 (1.3%) of 604 control sera reacted with HNE in at least 1 assay, 3 (0.5%) reacted in 2 assays, and only 1 serum sample (0.16%) reacted in all 3 assays. Sera obtained from patients with WG or MPA were universally HNE ANCA-negative, as were sera obtained from healthy controls.

CONCLUSION

Optimal sensitivity for HNE ANCA requires multimodality testing. HNE ANCAs are frequent in CIMDL but not in other autoimmune diseases, including classic ANCA-associated vasculitis. HNE ANCAs may discriminate between CIMDL and WG, whereas a positive test result for PR3 ANCA may not.

Apoptosis-induced proteinase 3 membrane expression is independent from degranulation

Proteinase 3 (PR3) and human neutrophil elastase (HNE) are serine proteinases stored in the azurophilic granules of neutrophils. In contrast to HNE, PR3 is the target of antineutrophil cytoplasm antibodies (ANCA) in Wegener's granulomatosis. The mechanisms leading to the membrane expression of PR3 and HNE are still unclear and appear to be critical to understand the pathophysiological role of ANCA. Stably transfected rat basophilic cell lines (RBL) with PR3 or HNE were used to analyze the PR3 and HNE secretion mechanisms and differentiate between them. RBL cells were lacking endogenous PR3 and HNE. They were stably transfected with HNE or PR3 or an inactive mutant of PR3 (PR3S203A). Using the calcium ionophore A23187 as a secretagogue, higher serine proteinase activity was secreted in the supernatant of RBL/HNE than in RBL/PR3. It is interesting that PR3 and PR3/S203A were also expressed at the plasma membrane, thus demonstrating that serine protease activity was not required for plasma membrane expression. In contrast, no expression of plasma membrane HNE could be detected in RBL/HNE. Apoptosis induced by etoposide was evaluated by DNA fragmentation, the presence of cytoplasmic histone-associated DNA fragments, and annexin V labeling. No membrane HNE was detected in RBL/HNE. In contrast, in RBL/PR3 and in RBL/PR3S203A, the membrane expression of PR3 and PR3S203A increased with etoposide concentrations and appeared closely related to annexin V labeling. Our data suggest that membrane PR3 originates from two distinct pools, the granular pool mobilized following degranulation or a plasma membrane pool mobilized upon apoptosis.

Neutrophil elastase up-regulates human beta-defensin-2 expression in human bronchial epithelial cells

Human beta-defensin-2 (HBD-2) gene expression is induced by tumour necrosis factor-alpha, interleukin-1beta and lipopolysaccharide. The objective of this study was to investigate the effect of neutrophil elastase (NE), a major pro-inflammatory protease, on HBD-2 expression. HBD-2 gene expression was assessed by reverse transcription polymerase chain reaction in the human bronchial epithelial cell line 16HBE14o- and primary normal human bronchial epithelial (NHBE) cells. Optimal HBD-2 expression was induced with 100 nM NE. Using a HBD-2-luciferase reporter construct, luciferase activity increased significantly in 16HBE14o- cells following incubation with NE. An increase in HBD-2 protein expression was observed in primary NHBE cells after incubation with NE as assessed by laser scanning cytometry. In conclusion, NE up-regulates HBD-2 expression in bronchial epithelial cells.

Cellular and molecular abnormalities in severe congenital neutropenia predisposing to leukemia

Severe congenital neutropenia (SCN) is a rare hematological disease characterized by a selective decrease in the level of circulating neutrophils in peripheral blood, maturation arrest at the promyelocyte stage of differentiation in the bone marrow, recurrent severe infections, and evolution to acute myelogenous leukemia (AML). Cellular and molecular studies of 12 SCN patients, including 5 patients that evolved to develop AML, revealed impaired proliferative characteristics and accelerated apoptosis of bone marrow progenitor cells in SCN compared with 11 healthy controls as demonstrated by flow cytometry analysis. Sequencing analysis revealed heterozygous deletion or substitution mutations in the neutrophil elastase (NE) gene in 9 of 12 patients but not in healthy controls. Expression of various NE mutants, but not normal NE, resulted in accelerated apoptosis of human promyelocytic HL-60 progenitor cells, similar to impaired survival observed in patients' cells. Bone marrow-derived primitive CD34(+) and CD33(+)/CD34(-) progenitor cells from SCN patients evolving to AML, all with mutations in the granulocyte colony-stimulating factor receptor (G-CSFR) gene, demonstrated normal cell survival, whereas more differentiated CD15(+)/CD33(-)/CD34(-) cells negative for mutant G-CSFR gene, continue to exhibit accelerated apoptosis. These data demonstrate that impaired survival of bone marrow myeloid progenitor cells, probably driven by expression of mutant NE, is the cellular mechanism responsible for neutropenia in SCN. Furthermore, our results suggest that acquired G-CSFR mutations may initiate signaling events that override the pro-apoptotic effect of mutant NE in primitive progenitor cells, resulting in an expansion of the abnormal AML clone.

Differential gene expression underlying the functional distinctions of primary human CD34+ hematopoietic stem and progenitor cells from peripheral blood and bone marrow

The restorative capacity of human CD34(+) hematopoietic cells is clinically used in the autologous and allogeneic transplant setting to support cytotoxic therapy. We examined gene expression patterns of highly enriched bone marrow CD34(+) (BM-CD34(+)) or G-CSF-mobilized peripheral blood CD34(+) (PB-CD34(+)) cells by cDNA array technology, quantitative real-time RT-PCR, and flow cytometry, to identify molecular causes underlying the functional differences between circulating and sedentary hematopoietic stem and progenitor cells. The greater cell cycle and DNA synthesis activity of BM-CD34(+) compared to PB-CD34(+) cells was reflected by the 2- to 5-fold higher expression of 9 genes involved in cell cycle, 11 genes regulating DNA synthesis, and the cell cycle-initiating transcription factor E2F-1. The 2- to 3-fold greater expression of 5 pro-apoptotic genes in PB-CD34(+) cells indicated a higher apoptotic activity, which could functionally be corroborated by apoptosis assays. Thrombin receptor (PAR1), known to play a role in trafficking of malignant cells, was 3.6-fold higher expressed in circulating CD34(+) cells than in BM-CD34(+) cells. Guidance via thrombin receptor might molecularly mediate stem cell migration. In summary, our study provides gene expression profiles of primary human CD34(+) hematopoietic cells of blood and marrow. Our data molecularly confirm and explain the finding that CD34(+) cells residing in the bone marrow are cycling more rapidly, whereas circulating CD34(+) cells consist of a higher number of quiescent stem and progenitor cells. Moreover, our data give novel molecular insights into stem cell migration and differentiation.

Effects of carboxy-terminal modifications of proteinase 3 (PR3) on the recognition by PR3-ANCA

BACKGROUND

Autoantibodies directed against neutrophil proteinase 3 (PR3-ANCA) from patients with Wegener's granulomatosis and microscopic polyangiitis recognize conformational epitopes of PR3. During maturation of neutrophils, PR3 undergoes amino-terminal and carboxy-terminal processing. In contrast to amino-terminal processing, the effects of carboxy-terminal processing on recognition of PR3 by PR3-ANCA remain unknown. Carboxy-terminally modified or tagged recombinant PR3 (rPR3) molecules may be useful for the refinement of diagnostic assays and for the study of biological processes.

METHODS

This study was designed to determine whether 293 cells can be used to express specifically designed carboxy-terminal variants of rPR3, and to evaluate the effects of different carboxy-terminal modifications on the recognition by PR3-ANCA in the capture ELISA.

RESULTS

The rPR3-variants secreted into the media supernatants of transfected 293 cells escaped proteolytic processing. Furthermore, in contrast to the effects of amino-terminal pro-peptide deletion on PR3-ANCA binding, carboxy-terminal modifications (deletion and additions) did not significantly affect recognition by PR3-ANCA.

CONCLUSIONS

This expression system is ideally suited for the expression of custom-designed carboxy-terminal rPR3 variants, and major conformational effects of carboxy-terminal modifications seem unlikely.

Neutrophil transendothelial migration and alteration in vascular permeability: focus on neutrophil-derived azurocidin

Infiltration and accumulation of polymorphonuclear leukocytes within the tissues is a hallmark of the acute inflammatory response. A prominent feature of acute inflammation is enhanced vascular permeability resulting in edema formation. Such changes in vascular permeability have been known to be dependent upon polymorphonuclear leukocyte interactions with the vascular endothelium. Careful investigation has shown clearly that permeability changes can occur without polymorphonuclear leukocyte transendothelial migration, and that polymorphonuclear leukocyte migration can occur without permeability alteration. The underlying mechanisms of polymorphonuclear leukocyte-stimulated changes in endothelial barrier function have remained elusive. Endothelial activation and polymorphonuclear leukocyte adhesion to the endothelium are both required for polymorphonuclear leukocyte-induced changes in vascular permeability. Polymorphonuclear leukocyte-derived azurocidin plays a major role in this polymorphonuclear leukocyte-evoked alteration in endothelial permeability. Azurocidin is released after activation of polymorphonuclear leukocytes, such as after ligation of the major adhesive integrin CD11b/CD18. Understanding how polymorphonuclear leukocytes alter vascular permeability may provide targets for new drugs for appropriate therapeutic intervention in acute and chronic inflammatory diseases. This review focuses on the role of polymorphonuclear leukocyte-derived azurocidin in alteration of vascular permeability.

Structural analysis of N-glycans from human neutrophil azurocidin

N-glycans of human neutrophil azurocidin, enzymatic inactive homolog of serine proteinase playing important and multifunctional roles in antimicrobial defense, endotoxin binding, monocyte, and T-cell activation, were isolated by hydrazinolysis and fluorescence labeled. An ion-exchange chromatography on GlycoSep C column separated neutral, mono-, and disialylated glycans. The glycans from each group were separated subsequently on GlycoSep N and GlycoSep H columns. Sequential exoglycosidase treatment and HPLC mapping allowed determining 21 different glycan structures, majority of them being neutral (79.8%), the rest-mono- (13.1%) and disialylated (1.2%).

Gene expression profiling identifies significant differences between the molecular phenotypes of bone marrow-derived and circulating human CD34+ hematopoietic stem cells

CD34+ hematopoietic stem cells are used clinically to support cytotoxic therapy, and recent studies raised hope that they could even serve as a cellular source for nonhematopoietic tissue engineering. Here, we examined in 18 volunteers the gene expressions of 1185 genes in highly enriched bone marrow CD34+ (BM-CD34+) or granulocyte-colony-stimulating factor-mobilized peripheral blood CD34+ (PB-CD34+) cells by means of cDNA array technology to identify molecular causes underlying the functional differences between circulating and sedentary hematopoietic stem and progenitor cells. In total, 65 genes were significantly differentially expressed. Greater cell cycle and DNA synthesis activity of BM-CD34+ than PB-CD34+ cells were reflected by the 2- to 5-fold higher expression of 9 genes involved in cell cycle progression, 11 genes regulating DNA synthesis, and cell cycle-initiating transcription factor E2F-1. Conversely, 9 other transcription factors, including the differentiation blocking GATA2 and N-myc, were expressed 2 to 3 times higher in PB-CD34+ cells than in BM-CD34+ cells. Expression of 5 apoptosis driving genes was also 2 to 3 times greater in PB-CD34+ cells, reflecting a higher apoptotic activity. In summary, our study provides a gene expression profile of primary human CD34+ hematopoietic cells of the blood and marrow. Our data molecularly confirm and explain the finding that CD34+ cells residing in the bone marrow cycle more rapidly, whereas circulating CD34+ cells consist of a higher number of quiescent stem and progenitor cells. Moreover, our data provide novel molecular insight into stem cell physiology.

Mutations in the neutrophil elastase gene in cyclic and congenital neutropenia

Severe neutropenia disorders are characterized by extremely low levels of peripheral blood neutrophils, a maturation block of bone marrow progenitor cells and recurring severe bacterial and fungal infections. Recent reports indicated that severe neutropenia is a consequence of an impaired survival and abnormal cell cycle progression of myeloid progenitor cells in both cyclic and severe congenital neutropenia. Mutations in the neutrophil elastase gene were identified in all patients with cyclic neutropenia and most of the patients with severe congenital neutropenia. We hypothesize that expression of mutant neutrophil elastase protein results in deregulation of intracellular activity and premature cell death of myeloid-committed progenitor cells in these disorders, resulting in the lack of peripheral blood neutrophils. The potential molecular mechanisms of mutant-protein-mediated neutropenia is discussed.

Antineutrophil cytoplasmic antibodies reacting with the pro form of proteinase 3 and disease activity in patients with Wegener's granulomatosis and microscopic polyangiitis

OBJECTIVE

Antineutrophil cytoplasmic antibodies (ANCA) directed against proteinase 3 (PR3) are diagnostic markers for the small vessel vasculitides Wegener's granulomatosis (WG) and microscopic polyangiitis (MPA). Correlation of disease activity with PR3 ANCA levels, as determined by standard methods, is not apparent in every patient. PR3 ANCA react with yet to be identified conformational epitopes. We have identified PR3 ANCA subsets that react differentially with mature recombinant PR3 (rPR3; lacking the N-terminal activation dipeptide) and the pro form of this enzyme (pro-rPR3). The present study was performed to determine the association of these PR3 ANCA subsets with disease activity.

METHODS

Sera from 61 PR3 ANCA-positive patients with WG or MPA were assayed by capture enzyme-linked immunosorbent assay using pro-rPR3 and rPR3 as target antigens, and were correlated with disease activity as determined by the Birmingham Vasculitis Activity Score (BVAS).

RESULTS

Median levels of PR3 ANCA reacting with pro-rPR3 were higher during active (n = 32) than during inactive (n = 29) disease (P = 0.016). Reactivity with mature rPR3 was not significantly different (P = 0.71). Serial followup in individual patients also indicated better correlation of PR3 ANCA reactivity with pro-rPR3 than with mature rPR3.

CONCLUSION

PR3 ANCA subsets reactive with epitopes accessible on pro-PR3 correlate better with disease activity than do subsets reactive with epitopes accessible only on mature PR3. This observation may explain why ANCA levels determined with current standard methods are suboptimal for monitoring disease activity. It raises new questions about the primary target of the PR3 ANCA immune response in patients with small vessel vasculitis.

Internalization of proteinase 3 is concomitant with endothelial cell apoptosis and internalization of myeloperoxidase with generation of intracellular oxidants

The important issue addressed by the studies presented here is the mechanism of neutrophil-mediated damage to endothelial and epithelial cells during inflammation. Binding of neutrophil-released granule proteins to endothelial cells may be involved in vascular damage in patients with inflammatory vascular diseases. We have determined whether granule proteins proteinase 3(PR3) and/or myeloperoxidase (MPO) are internalized into endothelial cells, as examined by UV light, confocal, and electron microscopy. Coincident induction of apoptosis and/or the generation of intracellular oxidants were monitored. The results indicate that human endothelial cells (human umbilical vein endothelial cells, human umbilical arterial endothelial cells, human lung microvascular endothelial cells) internalize both PR3 and MPO, which are detected on the cell surface, in the cytoplasm, and possibly nuclear. Epithelial cells (small airway epithelial cells) internalized MPO but not PR3, implying that the mechanism of PR3 internalization may be cell-type specific and different from that of MPO. Internalization of PR3, but not MPO, correlated with activation of apoptosis. Internalization of MPO correlated with an increase in intracellular oxidant radicals. The requirement for the proteolytic activity of PR3 for the induction of apoptosis was examined by generating PR3-truncated fragments that did not contain the components of the catalytic triad. An apoptotic function was localized to the C-terminal portion of PR3. These studies reveal novel mechanisms by which the neutrophil granule proteins PR3 and MPO contribute to tissue injury at sites of inflammation.

The soluble endothelial protein C receptor binds to activated neutrophils: involvement of proteinase-3 and CD11b/CD18

The protein C pathway is a primary regulator of blood coagulation and a critical component of the host response to inflammatory stimuli. The most recent member of this pathway is the endothelial protein C receptor (EPCR), a type I transmembrane protein with homology to CD1d/MHC class I proteins. EPCR accelerates formation of activated protein C, a potent anticoagulant and antiinflammatory agent. The current study demonstrates that soluble EPCR binds to PMA-activated neutrophils. Using affinity chromatography, binding studies with purified components, and/or blockade with specific Abs, it was found that soluble EPCR binds to proteinase-3 (PR3), a neutrophil granule proteinase. Furthermore, soluble EPCR binding to neutrophils was partially dependent on Mac-1 (CD11b/CD18), a beta(2) integrin involved in neutrophil signaling, and cell-cell adhesion events. PR3 is involved in multiple diverse processes, including hemopoietic proliferation, antibacterial activity, and autoimmune-mediated vasculitis. The observation that soluble EPCR binds to activated neutrophils via PR3 and a beta(2) integrin suggests that there may be a link between the protein C anticoagulant pathway and neutrophil functions.

What you should know about PR3-ANCA. Conformational requirements of proteinase 3 (PR3) for enzymatic activity and recognition by PR3-ANCA

The neutrophil azurophil granule constituent proteinase 3 (PR3) is the principal antigen for anti-neutrophil cytoplasmic antibodies (ANCA) in Wegener's granulomatosis. The conformation of the mature PR3 enzyme results from intracellular post-translational processing. The nascent molecule undergoes proteolytic cleavage of the amino-terminal signal peptide and activation dipeptide and of a carboxy-terminal peptide extension. The conformation of PR3 is stabilized by four disulfide bonds and, to a lesser extent, by asparagine-linked glycosylation. Most anti-neutrophil cytoplasmic antibodies directed against proteinase 3 (PR3-ANCA) recognize conformational epitopes. The expression of recombinant PR3 has provided a better understanding of the significance of the various intracellular processing steps for enzymatic activity and recognition by PR3-ANCA.

Granulocyte-macrophage colony-stimulating factor (GM-CSF) but not granulocyte colony-stimulating factor (G-CSF) induces plasma membrane expression of proteinase 3 (PR3) on neutrophils in vitro

The theoretical risk of triggering vasculitis resulting from administration of G-CSF and GM-CSF to patients with anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitides (AAV), such as Wegener's granulomatosis (WG), who develop agranulocytosis due to cytotoxic therapy, is unknown. Since there is strong evidence that activation of polymorphonuclear neutrophils (PMN) induced by binding of ANCA to PR3 or myeloperoxidase (MPO) expressed on their plasma membrane is involved in the pathogenesis of systemic vasculitides (SV), we studied the surface expression of PR3 and MPO on PMN from healthy donors in response to G-CSF and GM-CSF in vitro by flow cytometric analysis. Increasing doses of G-CSF did not alter PR3 expression on either untreated or tumour necrosis factor-alpha (TNF-alpha)-primed donor PMN significantly. In contrast, GM-CSF significantly increased PR3 membrane expression on both intact PMN and neutrophils primed with TNF-alpha. MPO expression was not significantly altered by either G-CSF or GM-CSF. In summary, these data demonstrate that GM-CSF, but not G-CSF, induces plasma membrane expression of PR3 on PMN in vitro. Since in AAV accessibility of the antigen (PR3 or MPO) to the antibody (ANCA) on the plasma membrane of PMN is thought to be essential for neutrophil activation by ANCA, the results of the present study suggest that administration of GM-CSF to patients with WG with neutropenia implies a definite theoretical risk of deterioration of vasculitis via this mechanism.

Changes in Chromatin Organization at the Neutrophil Elastase Locus Associated With Myeloid Cell Differentiation

Neutrophil elastase, proteinase-3, and azurocidin are primary components of neutrophil azurophilic granules and are encoded by closely linked genes (gene symbols ELA2, PRTN3, and AZU1, respectively) in a region of approximately 50 kb. These genes are coordinately expressed in a granulocyte-specific fashion, but the mechanisms defining this pattern of expression are unknown. To understand the role of chromatin organization in governing the expression of ELA2, PRTN3, and AZU1, we mapped this region of chromosome 19 and identified the adipsin (complement factor D) gene in proximity to the 3′ end of ELA2. We then examined the changes in chromatin structure at the locus which accompany myeloid cell differentiation and identified 17 DNase I hypersensitive sites (DHS 1 to 17) in U-937 cells, an early myelomonocytic cell line expressing high levels of neutrophil elastase. Chemically induced differentiation and concomitant downregulation of AZU1, PRTN3, and ELA2 transcription in U-937 cells is not accompanied by changes in the DHS-pattern. Mature neutrophils, however, do not carry any of these hypersensitive sites, indicating a large degree of chromatin remodeling at this locus accompanying terminal granulocytic differentiation. Sixteen of the 17 DHS identified in U-937 cells are also present in the HL-60 myelomonocytic cell line. Hematopoietic cell lines representing the early erythroid and lymphocyte lineages, and a nonhematopoietic cell line display a subset of the hypersensitive sites. The altered chromatin structure specific to cells that actively transcribe the AZU1-PRTN3-ELA2 genes suggests that chromatin reorganization is an important mechanism regulating the myeloid-specific transcription of this gene cluster.

Changes in Chromatin Organization at the Neutrophil Elastase Locus Associated With Myeloid Cell Differentiation

Neutrophil elastase, proteinase-3, and azurocidin are primary components of neutrophil azurophilic granules and are encoded by closely linked genes (gene symbols ELA2, PRTN3, and AZU1, respectively) in a region of approximately 50 kb. These genes are coordinately expressed in a granulocyte-specific fashion, but the mechanisms defining this pattern of expression are unknown. To understand the role of chromatin organization in governing the expression of ELA2, PRTN3, and AZU1, we mapped this region of chromosome 19 and identified the adipsin (complement factor D) gene in proximity to the 3′ end of ELA2. We then examined the changes in chromatin structure at the locus which accompany myeloid cell differentiation and identified 17 DNase I hypersensitive sites (DHS 1 to 17) in U-937 cells, an early myelomonocytic cell line expressing high levels of neutrophil elastase. Chemically induced differentiation and concomitant downregulation of AZU1, PRTN3, and ELA2 transcription in U-937 cells is not accompanied by changes in the DHS-pattern. Mature neutrophils, however, do not carry any of these hypersensitive sites, indicating a large degree of chromatin remodeling at this locus accompanying terminal granulocytic differentiation. Sixteen of the 17 DHS identified in U-937 cells are also present in the HL-60 myelomonocytic cell line. Hematopoietic cell lines representing the early erythroid and lymphocyte lineages, and a nonhematopoietic cell line display a subset of the hypersensitive sites. The altered chromatin structure specific to cells that actively transcribe the AZU1-PRTN3-ELA2 genes suggests that chromatin reorganization is an important mechanism regulating the myeloid-specific transcription of this gene cluster.

Proteinase 3, a potent secretagogue in airways, is present in cystic fibrosis sputum

We evaluated the roles of proteinase 3 (PR3) and human neutrophil elastase (HNE), two neutrophil serine proteinases in the mechanisms leading to airway inflammation and hypersecretion in cystic fibrosis (CF). Using specific enzyme-linked immunosorbent assay (ELISA), we found higher levels of PR3 than HNE in sputum from CF patients. Using two inhibitors, ICI (Imperial Chemical Industries) 200,355 (which inhibits both HNE and PR3) and secretory leukoproteinase inhibitor (SLPI) (which inhibits only HNE), we showed that PR3 was enzymatically active in sputum, and its activity, as assessed by SLPI-resistant serine proteinase activity, correlated highly with its antigenic concentration measured by ELISA. Interestingly, sputum pellet-associated serine proteinase activity was mostly due to HNE. PR3 purified from neutrophil azurophil granules triggered airway gland secretion, as measured by the release of radiolabeled molecules from cultured bovine tracheal serous cells pulse-labeled with Na235SO4. This secretory activity was inhibited by ICI 200,355. PR3 concentration in CF sputum was highly correlated with taurine concentration, a reliable marker of airway inflammation and respiratory scores (e.g., FEV1%), whereas no significant correlation was observed with HNE. We verified that Pseudomonas aeruginosa proteinases did not interfere with the assessment of PR3 and HNE. Indeed, the PR3/HNE ratio was greatest in patients chronically infected by P. aeruginosa. We suggest that PR3 may play a role in the hypersecretory process that is characteristic of CF.

Interaction of purified human proteinase 3 (PR3) with reconstituted lipid bilayers

Proteinase 3 (PR3), the major target autoantigen in Wegener's granulomatosis is a serine proteinase that is normally stored intracellularly in the primary granules of quiescent neutrophils and monocytes. Upon cell activation, a significant portion of this antigen is detected on the cell surface membrane. The nature of the association of PR3 with the membrane and its functional significance are unknown. We investigated the interaction of purified human PR3 with mixtures of zwitterionic (dimyristoyl-L-alpha-phosphatidylcholine, DMPC) and anionic (dimyristoyl-L-alpha-phosphatidylglycerol, DMPG) phospholipids in reconstituted lipid bilayers using differential scanning calorimetry and lipid photolabeling, and measured the affinity of this interaction using spectrophotometry. Two other primary granule constituents, human neutrophil elastase (HNE) and myeloperoxidase (MPO) were investigated for comparison. In calorimetric assays, using lipid vesicles of mixed DMPC/DMPG, increasing PR3 concentrations (protein/lipid molar ratio from 0 to 1 : 110) induced a significant decrease of the main chain transition enthalpy and a shift in chain melting temperatures which is indicative of partial insertion of PR3 into the hydrophobic region of the lipid membranes. This was confirmed by hydrophobic photolabeling using liposomes containing trace amounts of the photoactivable [125I]-labeled phosphatidylcholine analog TID-PC/16. The molar affinity of PR3, HNE, and MPO to lipid vesicles of different DMPC/DMPG ratios was then determined by spectrophotometry. At a DMPC/DMPG ratio of 1 : 1, molar affinities of PR3, Kd = 4.5 +/- 0.3 microm; HNE, 14.5 +/- 1.2 microm; and MPO, 50 +/- 5 microm (n = 3) were estimated. The lipid-associated PR3 exhibited two-fold lower Vmax and Km values, and its enzyme activity was slightly more inhibited (Ki) by the natural alpha1-proteinase inhibitor (alpha1-PI) or an autoantibody to PR3.

On the Role of the Proform-Conformation for Processing and Intracellular Sorting of Human Cathepsin G

The serine protease cathepsin G is synthesized during the promyelomonocytic stage of neutrophil and monocyte differentiation. After processing, including removal of an amino-terminal propeptide from the catalytically inactive proform, the active protease acquires a mature conformation and is stored in azurophil granules. To investigate the importance of the proform-conformation for targeting to granules, a cDNA encoding a double-mutant form of human preprocathepsin G lacking functional catalytic site and amino-terminal prodipeptide (CatG/Gly201/▵Gly19Glu20) was constructed, because we were not able to stably express a mutant lacking only the propeptide. Transfection of the cDNA to the rat basophilic leukemia RBL-1 and the murine myeloblast-like 32D cl3 cell lines resulted in stable, protein-expressing clones. In contrast to wild-type proenzyme, CatG/Gly201/▵Gly19Glu20 adopted a mature conformation cotranslationally, as judged by the early acquisition of affinity to the serine protease inhibitor aprotinin, appearing before the carboxyl-terminal processing and also in the presence of the Golgi-disrupting agent brefeldin A. The presence of a mature amino-terminus was confirmed by amino-terminal radiosequencing. As with wild-type proenzyme, CatG/Gly201/▵Gly19Glu20 was proteolytically processed carboxyl-terminally and glycosylated with asparagine-linked carbohydrates that were converted into complex forms. Furthermore, it was targeted to granules, as determined by subcellular fractionation. Our results show that the initial proform-conformation is not critical for intracellular sorting of human cathepsin G. Moreover, we demonstrate that double-mutant cathepsin G can achieve a mature conformation before carboxyl-terminal processing of the proform.

© 1998 by The American Society of Hematology.

On the Role of the Proform-Conformation for Processing and Intracellular Sorting of Human Cathepsin G

The serine protease cathepsin G is synthesized during the promyelomonocytic stage of neutrophil and monocyte differentiation. After processing, including removal of an amino-terminal propeptide from the catalytically inactive proform, the active protease acquires a mature conformation and is stored in azurophil granules. To investigate the importance of the proform-conformation for targeting to granules, a cDNA encoding a double-mutant form of human preprocathepsin G lacking functional catalytic site and amino-terminal prodipeptide (CatG/Gly201/▵Gly19Glu20) was constructed, because we were not able to stably express a mutant lacking only the propeptide. Transfection of the cDNA to the rat basophilic leukemia RBL-1 and the murine myeloblast-like 32D cl3 cell lines resulted in stable, protein-expressing clones. In contrast to wild-type proenzyme, CatG/Gly201/▵Gly19Glu20 adopted a mature conformation cotranslationally, as judged by the early acquisition of affinity to the serine protease inhibitor aprotinin, appearing before the carboxyl-terminal processing and also in the presence of the Golgi-disrupting agent brefeldin A. The presence of a mature amino-terminus was confirmed by amino-terminal radiosequencing. As with wild-type proenzyme, CatG/Gly201/▵Gly19Glu20 was proteolytically processed carboxyl-terminally and glycosylated with asparagine-linked carbohydrates that were converted into complex forms. Furthermore, it was targeted to granules, as determined by subcellular fractionation. Our results show that the initial proform-conformation is not critical for intracellular sorting of human cathepsin G. Moreover, we demonstrate that double-mutant cathepsin G can achieve a mature conformation before carboxyl-terminal processing of the proform.

© 1998 by The American Society of Hematology.

Inhibition of human leukocyte proteinase 3 by a novel recombinant serine proteinase inhibitor (LEX032)

The interaction of a bioengineered serpin (LEX032) with human leukocyte proteinase 3 (PR 3) has been investigated. LEX032 was found to be a time-dependent inhibitor of PR 3, forming a highly-stable enzyme-inhibitor complex (Ki 12 nM).

Human dipeptidyl-peptidase I. Gene characterization, localization, and expression

Dipeptidyl-peptidase I, a lysosomal cysteine proteinase, is important in intracellular degradation of proteins and appears to be a central coordinator for activation of many serine proteinases in immune/inflammatory cells. Little is known about the molecular genetics of the enzyme. In the present investigation the gene for dipeptidyl-peptidase I was cloned and characterized. The gene spans approximately 3.5 kilobases and consists of two exons and one intron. The genomic organization is distinct from the complex structures of the other members of the papain-type cysteine proteinase family. By fluorescence in situ hybridization, the gene was mapped to chromosomal region 11q14.1-q14.3. Analysis of the sequenced 5'-flanking region revealed no classical TATA or CCAAT box in the GC-rich region upstream of cap site. A number of possible regulatory elements that could account for tissue-specific expression were identified. Northern analyses demonstrated that the dipeptidyl-peptidase I message is expressed at high levels in lung, kidney, and placenta, at moderate to low levels in many organs, and at barely detectable levels in the brain, suggesting tissue-specific regulation. Among immune/inflammatory cells, the message is expressed at high levels in polymorphonuclear leukocytes and alveolar macrophages and their precursor cells. Treatment of lymphocytes with interleukin-2 resulted in a significant increase in dipeptidyl-peptidase I mRNA levels, suggesting that this gene is subjected to transcriptional regulation. The results provide initial insights into the molecular basis for the regulation of human dipeptidyl-peptidase I.

Rupture of a hepatic artery aneurysm caused by Wegener's granulomatosis

Among vasculitis syndromes Wegener's granulomatosis (WG) is characterized by involvement of the upper and lower airways and kidneys. The associated vasculitis involves small and medium sized arteries and veins. Aneurysm formation and a segmental pattern of involvement of larger arteries is not typically seen in WG--a presentation more in keeping with polyarteritis nodosa. We report on a patient hospitalized with classical manifestations of WG who died suddenly of hypovolemic shock caused by intraperitoneal hemorrhage resulting from rupture of a hepatic artery aneurysm. The aneurysm was caused by involvement of the hepatic artery in the disease process. To our knowledge aneurysmatic dilatation of the hepatic artery due to WG has not been previously described. This case illustrates an unusual disease course in WG and the overlap which exists in classical vasculitis syndromes.

Human leukocyte elastase is an endogenous ligand for the integrin CR3 (CD11b/CD18, Mac-1, alpha M beta 2) and modulates polymorphonuclear leukocyte adhesion

Integrin CR3 (CD11b/CD18, Mac-1, alpha M beta 2) mediates the transient adhesion of polymorphonuclear leukocytes (PMN) to surfaces coated with fibrinogen, C3bi, ICAM-1, and other ligands. Recent studies (Cai, T.-Q., and S.D. Wright 1995. J. Biol. Chem. 270:14358) suggest that adhesion may be favored by stimulus-dependent changes in the kinetics of ligand binding by CR3. Cell detachment, on the other hand, must occur by a different mechanism because binding kinetics cannot affect cell adhesion after binding of ligand has occurred. We have sought a mechanism that would reverse binding of ligand to CR3 and report here that lysates of PMN contain an endogenous ligand that binds CR3 and competes the binding of C3bi. Purification and sequence analysis identified the structurally homologous azurophilic granule proteins, elastase, protease 3, and azurocidin as candidates. Studies with purified elastase and azurocidin showed that each bound specifically to purified, immobilized CR3. Elastase may play a role in modulating integrin-mediated cell adhesion because it is expressed at the cell surface, and the expression level is inversely proportional to cell adhesivity. Furthermore, a monoclonal antibody against elastase prevented detachment of PMN from fibrinogen-coated surfaces and blocked chemotaxis, confirming a role for this protein in regulating integrin-mediated adhesion. These studies suggest a model for release of integrin-mediated cell adhesion in which endogenous ligands such as elastase may release adhesion by "'eluting" substrate-bound ligand. A role for the proteolytic activity of elastase appears likely but is not demonstrated in this study.