Serine proteinases of mast cell and leukocyte granules. A league of their own

Nonlinear effects of environmental salinity on the gill transcriptome versus proteome of Oreochromis niloticus modulate epithelial cell turnover

A data-independent acquisition (DIA) assay library for targeted quantitation of thousands of Oreochromis niloticus gill proteins using a label- and gel-free workflow was generated and used to compare protein and mRNA abundances. This approach generated complimentary rather than redundant data for 1899 unique genes in gills of tilapia acclimated to freshwater and brackish water. Functional enrichment analyses identified mitochondrial energy metabolism, serine protease and immunity-related functions, and cytoskeleton/ extracellular matrix organization as major processes controlled by salinity in O. niloticus gills. Non-linearity in salinity-dependent transcriptome versus proteome regulation was revealed for specific functional groups of genes. The relationship was more linear for other molecular functions/ cellular processes, suggesting that the salinity-dependent regulation of O. niloticus gill function relies on post-transcriptional mechanisms for some functions/ processes more than others. This integrative systems biology approach can be adopted for other tissues and organisms to study cellular dynamics for many changing ecological contexts.

Persistent Severe Fixed Airways Obstruction in a High-Dosing E-cigarette User

Electronic Nicotine Delivery Systems (ENDS), commonly referred to as "e-cigs," were first introduced in the United States in 2007. Since then, their use has grown substantially, with the largest market among adolescents and young adults. ENDS are often perceived by the public as safe alternatives to traditional cigarettes and as aids in smoking cessation. Little is known about inhalational hazards of e-cigs. We describe the case of a 45-year-old man who developed acute respiratory symptoms associated with onset of severe fixed airways obstruction 9 months after he quit traditional cigarettes and began high-dose vaping. Lung biopsy showed respiratory bronchiolitis. Analysis of his heated e-cigarette solution identified a mixture containing vanillin, aldehydes, alcohols and other chemicals, the inhalation effects of which have not been well-studied. This case report adds to the growing literature describing potentially severe lung health effects of vaping and provides a framework for taking a clinical vaping history so that the health consequences of e-cigarettes may be better understood.

Tryptase as a polyfunctional component of mast cells

Mast cells are haematopoietic cells that arise from pluripotent precursors of the bone marrow. They play immunomodulatory roles in both health and disease. When appropriately activated, mast cells undergo degranulation, and preformed granule compounds are rapidly released into the surroundings. In many cases, the effects that mast cells have on various inflammatory settings are closely associated with the enzymatic characteristics of tryptase, the main granule compound of mast cells. Tryptase degranulation is often linked with the development of an immune response, allergy, inflammation, and remodelling of tissue architecture. Tryptase also represents an informative diagnostic marker of certain diseases and a prospective target for pharmacotherapy. In this review, we discuss the current knowledge about mast cell tryptase as one of the mast cell secretome proteases. The main points of the reviewed publications are highlighted with our microscopic images of mast cell tryptases visualized using immunohistochemical staining.

E-Cigarette Use Causes a Unique Innate Immune Response in the Lung, Involving Increased Neutrophilic Activation and Altered Mucin Secretion

RATIONALE

E-cigarettes have become increasingly popular and little is known about their potential adverse health effects.

OBJECTIVES

To determine the effects of e-cigarette use on the airways.

METHODS

Induced sputum samples from cigarette smokers, e-cigarette users, and nonsmokers were analyzed by quantitative proteomics, and the total and individual concentrations of mucins MUC5AC and MUC5B were determined by light scattering/refractometry and labeled mass spectrometry, respectively. Neutrophil extracellular trap (NET) formation rates were also determined for the same groups.

MEASUREMENTS AND MAIN RESULTS

E-cigarette users exhibited significant increases in aldehyde-detoxification and oxidative stress-related proteins associated with cigarette smoke compared with nonsmokers. The levels of innate defense proteins associated with chronic obstructive pulmonary disease, such as elastase and matrix metalloproteinase-9, were significantly elevated in e-cigarette users as well. E-cigarette users' sputum also uniquely exhibited significant increases in neutrophil granulocyte-related and NET-related proteins, such as myeloperoxidase, azurocidin, and protein-arginine deiminase 4, despite no significant elevation in neutrophil cell counts. Peripheral neutrophils from e-cigarette users showed increased susceptibility to phorbol 12-myristate 13-acetate-induced NETosis. Finally, a compositional change in the gel-forming building blocks of airway mucus (i.e., an elevated concentration of mucin MUC5AC) was observed in both cigarette smokers and e-cigarette users.

CONCLUSIONS

Together, our results indicate that e-cigarette use alters the profile of innate defense proteins in airway secretions, inducing similar and unique changes relative to cigarette smoking. These data challenge the concept that e-cigarettes are a healthier alternative to cigarettes.

Down-regulation of heat shock protein HSP90ab1 in radiation-damaged lung cells other than mast cells

Ionizing radiation (IR) leads to fibrosing alveolitis (FA) after a lag period of several weeks to months. In a rat model, FA starts at 8 weeks after IR. Before that, at 5.5 weeks after IR, the transcription factors Sp1 (stimulating protein 1) and AP-1 (activator protein 1) are inactivated. To find genes/proteins that were down-regulated at that time, differentially expressed genes were identified in a subtractive cDNA library and verified by quantitative RT-PCR (reverse transcriptase polymerase chain reaction), western blotting and immunohistochemistry (IH). The mRNA of the molecular chaperone HSP90AB1 (heat shock protein 90 kDa alpha, class B member 1) was down-regulated 5.5 weeks after IR. Later, when FA manifested, HSP90ab1 protein was down-regulated by more than 90% in lung cells with the exception of mast cells. In most mast cells of the normal lung, both HSP90ab1 and HSP70, another major HSP, show a very low level of expression. HSP70 was massively up-regulated in all mast cells three months after irradiation whereas HSP90AB1 was up-regulated only in a portion of mast cells. The strong changes in the expression of central molecular chaperones may contribute to the well-known disturbance of cellular functions in radiation-damaged lung tissue.

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.

Nafamostat mesilate, a potent tryptase inhibitor, modulates periodontitis in rats

Previous reports have demonstrated increased tryptase-like proteolytic activity in the crevicular fluid of patients with periodontal disease. In the present study, we have investigated the effect of tryptase inhibition with nafamostat mesilate (NM, 6-amino-2-naphtlyl p-guanidinobenzoate dimethansulfonate) on the development of experimental periodontitis in rats. Eighty (80) male Wistar rats were randomly separated into four groups: Control group, NM group (daily 0.1 mg/kg body weight of NM, i.p.), Ligature group (ligature placed at lower right first molars), and NM+Ligature group. The amount of alveolar bone loss (ABL) around the mesial root surface of the first mandibulary molar, as well as the myeloperoxidase (MPO) activity, and total proteolytic activity [N-benzoyl-L: -arginine-p-nitroanilide (BApNA) substrate] were determined at 7 and 14 days. NM led to significantly (p < 0.05) decreased ABL in animals subjected to ligature-induced periodontitis. Tryptase inhibition prevented the onset of significant ABL at 7 days of experiment (0.44 ± 0.16 and 0.60 ± 0.22, p > 0.05, NM+Ligature and Control, respectively) and significantly decreased the ABL at 14 days (0.97 ± 0.17 versus 1.82 ± 0.26, p < 0.001, NM+Ligature versus Ligature, respectively). In addition, NM significantly decreased MPO and total proteolytic activity at 14 days (p < 0.05). These data provided evidence that tryptase inhibition with NM attenuates gingival granulocyte infiltration and ABL in an experimental model of periodontitis in rats.

Long-distance delivery of bacterial virulence factors by Pseudomonas aeruginosa outer membrane vesicles

Bacteria use a variety of secreted virulence factors to manipulate host cells, thereby causing significant morbidity and mortality. We report a mechanism for the long-distance delivery of multiple bacterial virulence factors, simultaneously and directly into the host cell cytoplasm, thus obviating the need for direct interaction of the pathogen with the host cell to cause cytotoxicity. We show that outer membrane-derived vesicles (OMV) secreted by the opportunistic human pathogen Pseudomonas aeruginosa deliver multiple virulence factors, including beta-lactamase, alkaline phosphatase, hemolytic phospholipase C, and Cif, directly into the host cytoplasm via fusion of OMV with lipid rafts in the host plasma membrane. These virulence factors enter the cytoplasm of the host cell via N-WASP-mediated actin trafficking, where they rapidly distribute to specific subcellular locations to affect host cell biology. We propose that secreted virulence factors are not released individually as naked proteins into the surrounding milieu where they may randomly contact the surface of the host cell, but instead bacterial derived OMV deliver multiple virulence factors simultaneously and directly into the host cell cytoplasm in a coordinated manner.

Topography and morphometry of intestinal mast cells in children with Hirschsprung's disease

Mast cells (MC) are source of many biological active compounds like cytokines, arachidonic acid derivates, proteoglicanes, prostaglandins, proteases, free oxygen radials, NGF, PAF and many more. The role of MC in pathogenesis of Hirschsprung's disease (HD) is not clear. Substances produced by MC may exert an important effect on embryology, growth, differentiation and regeneration of intestinal nervous system. Additionally, MC products modulate inflammation processes thus influencing on the clinical course of HD. Present study was established to evaluate the morphologic MC examination as a support of making diagnosis in HD. The MC topography and morphometry were evaluated in specimens collected from aganglionic colon of patients with diagnosed HD. The results were compared with corresponding data from normally innervated colon of patients suffering from constipation, and normal colon of children not presenting defecation problems. MC were visualized using indirect immunohistochemical method LSAB with mouse antibody against human tryptase. The MC visualized in submucosa and muscular layer in Hirschsprung's disease were significantly larger in comparison with control group (p<0.05). Also the number of MC/mm2 in mucosa and lamina propria in HD was significantly elevated (p<0.05). However, the MC density in submucosa was also higher but it was not high statistically significant. In muscular layer and in serosa density of MC/mm2 was not statistically significant. In the intestinal wall MC in aganglionic segment in Hirschsprung's disease are significantly activated comparing with normally innervated colon segments taken from the patients from other groups. This may confirm the role of MC both in pathogenesis of HD and in the reparation processes of bowel nervous system.

Discovery of Potent, Selective, Orally Active, Nonpeptide Inhibitors of Human Mast Cell Chymase

A series of beta-carboxamido-phosphon(in)ic acids (2) was identified as a new structural motif for obtaining potent inhibitors of human mast cell chymase. For example, 1-naphthyl derivative 5f had an IC50 value of 29 nM and (E)-styryl derivative 6g had an IC50 value of 3.5 nM. An X-ray structure for 5f.chymase revealed key interactions within the enzyme active site. Compound 5f was selective for inhibiting chymase versus eight serine proteases. Compound 6h was orally bioavailable in rats (F=39%), and orally efficacious in a hamster model of inflammation.

Cathepsin G: the significance in rheumatoid arthritis as a monocyte chemoattractant

Human cathepsin G (EC 3.4.21.20) has been reported to have the in vitro chemotactic activity for human monocytes. In this study, we examined the role of cathepsin G in monocyte involvement in joint inflammation of rheumatoid arthritis (RA) as a monocyte chemoattractant. Eighteen patients with RA and four patients with osteoarthritis (OA) were used in this study. Thiobenzylester substrate, Succ-Phe-Leu-Phe-S-Bzl, was used to measure the activity of cathepsin G in synovial fluids. Monocyte migration induced by cathepsin G and synovial fluids was assessed by a 48-well microchemotaxis chamber technique. Immunohistochemical staining was performed to determine the cellular origin of cathepsin G in RA synovial tissue. A very low activity of cathepsin G was detected in synovial fluids from patients with OA. On the other hand, significantly increased activity of cathepsin G was detected in patients with RA when compared with the value of OA patients. A considerable monocyte chemotactic activity was detected in the synovial fluid of RA patients, and the activity was partially decreased by the treatment with inhibitors for cathepsin G, alpha1-antichymotrypsin and phenylmethylsulfonyl fluoride. The activity of cathepsin G was significantly correlated with the neutrophil counts in synovial fluids and the concentration of interleukin-6. Immunohistochemical studies showed that cathepsin G was strongly expressed by synovial lining cells, and weakly expressed by macrophages and neutrophils in synovial tissues. This study indicates that the monocyte chemotactic activity of cathepsin G may have a role in the pathogenesis of RA synovial inflammation.

Pathological roles of angiotensin II produced by mast cell chymase and the effects of chymase inhibition in animal models

The discovery of a new angiotensin II (Ang II) pathway generated by mast cell chymase has highlighted new biological functions for Ang II that is not related to the classic renin-angiotensin system (RAS). The conversion of Ang I to II occurs not only via the plasma angiotensin converting enzyme (ACE) or tissue ACE but also via chymase produced in the mast cells of humans, monkeys, dogs, and hamsters. The conversion by chymase has been especially found in morbid tissues following the migration of mast cells. The newly discovered functions of chymase are discussed in this review. During the vascular narrowing that occurs after vein grafting or balloon injury in dogs, chymase activity and Ang II concentrations along with intimal proliferation are significantly increased and chymase inhibitors completely suppressed these increase, though ACE inhibitors are ineffective. Similar results have also been confirmed in the dog arteriovenous fistula stenosis model. In both human and animal aneurysmal aortas, chymase activity is significantly increased, and chymase inhibitor has been shown to prevent the development of aneurysms in dogs. Chymase is activated in diseased hearts, and chymase inhibitors reduce both the mortality rates after acute myocardial infarction and the cardiac fibrosis that leads to the development of cardiomyopathy in hamsters. Chymase is also a pro-angiogenic factor, since the injection of chymase strongly facilitates angiogenesis in hamsters. We propose that chymase inhibitors are effective in the prevention of multiple cardiovascular disorders, especially at the local event level without any effect on the systemic blood pressure.

Characterization of a Novel Filarial Serine Protease Inhibitor, Ov-SPI-1, from Onchocerca volvulus, with Potential Multifunctional Roles during Development of the Parasite

A novel filarial serine protease inhibitor (SPI) from the human parasitic nematode Onchocerca volvulus, Ov-SPI-1, was identified through the analysis of a molting third-stage larvae expressed sequence tag dataset. Subsequent analysis of the expressed sequence tag datasets of O. volvulus and other filariae identified four other members of this family. These proteins are related to the low molecular weight SPIs originally isolated from Ascaris suum where they are believed to protect the parasite from host intestinal proteases. The two Ov-spi transcripts are up-regulated in the molting larvae and adult stages of the development of the parasite. Recombinant Ov-SPI-1 is an active inhibitor of serine proteases, specifically elastase, chymotrypsin, and cathepsin G. Immunolocalization of the Ov-SPI proteins demonstrates that the endogenous proteins are localized to the basal layer of the cuticle of third-stage, molting third-stage, and fourth-stage larvae, the body channels and multivesicular bodies of third-stage larvae and the processed material found between the two cuticles during molting. In O. volvulus adult worms the Ov-SPI proteins are localized to the sperm and to eggshells surrounding the developing embryos. RNA interference targeting the Ov-spi genes resulted in the specific knockdown of the transcript levels of both Ov-spi-1 and Ov-spi-2, a loss of native proteins, and a significant reduction in both molting and viability of third-stage larvae. We suggest the Ov-SPI proteins play a vital role in nematode molting by controlling the activity of an endogenous serine protease(s). The localization data in adults also indicate that these inhibitors may be involved in other processes such as embryogenesis and spermatogenesis.

A novel, potent dual inhibitor of the leukocyte proteases cathepsin G and chymase: molecular mechanisms and anti-inflammatory activity in vivo

Certain leukocytes release serine proteases that sustain inflammatory processes and cause disease conditions, such as asthma and chronic obstructive pulmonary disease. We identified beta-ketophosphonate 1 (JNJ-10311795; RWJ-355871) as a novel, potent dual inhibitor of neutrophil cathepsin G (K(i) = 38 nm) and mast cell chymase (K(i) = 2.3 nm). The x-ray crystal structures of 1 complexed with human cathepsin G (1.85 A) and human chymase (1.90 A) reveal the molecular basis of the dual inhibition. Ligand 1 occupies the S(1) and S(2) subsites of cathepsin G and chymase similarly, with the 2-naphthyl in S(1), the 1-naphthyl in S(2), and the phosphonate group in a complex network of hydrogen bonds. Surprisingly, however, the carboxamido-N-(naphthalene-2-carboxyl)piperidine group is found to bind in two distinct conformations. In cathepsin G, this group occupies the hydrophobic S(3)/S(4) subsites, whereas in chymase, it does not; rather, it folds onto the 1-naphthyl group of the inhibitor itself. Compound 1 exhibited noteworthy anti-inflammatory activity in rats for glycogen-induced peritonitis and lipopolysaccharide-induced airway inflammation. In addition to a marked reduction in neutrophil influx, 1 reversed increases in inflammatory mediators interleukin-1alpha, interleukin-1beta, tissue necrosis factor-alpha, and monocyte chemotactic protein-1 in the glycogen model and reversed increases in airway nitric oxide levels in the lipopolysaccharide model. These findings demonstrate that it is possible to inhibit both cathepsin G and chymase with a single molecule and suggest an exciting opportunity in the treatment of asthma and chronic obstructive pulmonary disease.

Therapeutic applications of chymase inhibitors in cardiovascular diseases and fibrosis

Chymase activates not only angiotensin I to angiotensin II but also latent transforming growth factor-beta-binding protein to transforming growth factor-beta. In dog grafted veins, chymase activity and angiotensin II concentration along with vascular proliferation were significantly increased, while they were significantly suppressed by a chymase inhibitor. After balloon injury in dog arteries, chymase activity was significantly increased in the injured artery, and a chymase inhibitor and an angiotensin AT(1) receptor antagonist were effective in preventing the vascular proliferation, but an angiotensin-converting enzyme inhibitor was ineffective. In fibrotic models, the tissue fibrosis was reduced by chymase inhibitors. In adhesion models, the transforming growth factor-beta concentration and adhesion formation were suppressed by chymase inhibitors. Therefore, chymase inhibitors may be useful for preventing cardiovascular diseases and fibrosis via inhibition of angiotensin II formation and transforming growth factor-beta activation.

Role of mast cells and their mediators in failing myocardium under mechanical ventricular support

BACKGROUND

Mast cells have been implicated in tissue remodeling and fibroblast stimulation. We explored the effect of mechanical support by left ventricular assist device (LVAD) in failing myocardium and looked into grade and distribution of interstitial fibrosis, mast cell density, mast cell phenotypes and basic fibroblast growth factor (bFGF) expression pre- and post-LVAD.

METHODS

Myocardial tissue was obtained from 20 patients with end-stage cardiomyopathy at the time of LVAD implantation and LVAD removal and from 7 donor hearts not used for transplantation. Tissue sections were stained for mast cells using tryptase as a marker and the myocardial fibrosis was measured. Double staining for tryptase and chymase was performed for detection of chymase-positive mast cells. Fluorescent microscopy showed the relationship of mast cells to bFGF, and bFGF expression was quantified by Western blot.

RESULTS

There was a significant increase in mast cells in heart failure vs normal myocardium. A secondary increase in mast cells occurred after long-term (>40 days) support compared with matched pre-LVAD samples (mean +/- SEM; 57.4 +/- 8.6 cells/10 fields vs 45.1 +/- 7.6 SEM cells/10 fields, p < 0.01). The secondary increase in mast cells was associated specifically with an increase in chymase-negative mast cells (p < 0.01). These findings are statistically significant with concurrent decreased expression of bFGF and decreased fibrosis in the same patient tissues (p < 0.01).

CONCLUSIONS

We suggest that, under long-term support, there is a change in phenotypic expression in mast cells, which can alter fibroblast functions. The decreased myocardial bFGF levels might be the result of these phenotypically altered mast cells.

A Single Treatment With a Specific Chymase Inhibitor, TY-51184, Prevents Vascular Proliferation in Canine Grafted Veins

In this study, we evaluated whether a specific chymase inhibitor, TY-51184 (2-[4-(5-fluoro-3-methylbenzo[b]thiophen-2-yl)sulfonamido-3-methanesulfonylphenyl]oxazole-4-carboxylicacid), prevents the vascular proliferation in canine grafted veins. In the placebo-and chymase inhibitor-treated groups, the external jugular vein was infiltrated with saline and 10 microM TY-51184, respectively, and then it was grafted to the ipsilateral carotid artery. The non-surgical dogs were used as the control group. By 28 days after grafting, the chymase and ACE activities were significantly increased in the injured arteries. TY-51184 significantly reduced the chymase activity in the grafted veins, while it did not affect the ACE activity. The intimal areas in the placebo- and TY-51184-treated groups were 3.32 +/- 0.16 and 1.96 +/- 0.52 mm(2), respectively, and this difference was significant. The ratios of intimal area to medial area in the placebo- and TY-51184-treated groups were 66.8 +/- 3.5% and 34.9 +/- 9.2%, respectively, and this difference was also significant. There was a significant relationship between vascular proliferation and chymase activity, but not ACE activity. In this study, we demonstrated that a single treatment with a specific chymase inhibitor, TY-51184, could prevent the vascular proliferation in canine grafted veins.

Significance of chymase inhibition for prevention of adhesion formation

To clarify the role of chymase in adhesion formation, we investigated whether a chymase inhibitor could prevent adhesion formation after surgery in hamsters. Hamsters received a lesion produced by uterus scraping. A specific chymase inhibitor, 2-[4-(5-fluoro-3-methylbenzo[b]thiophen-2-yl)sulfonamido-3-methanesulfonylphenyl]oxazole-4-carboxylicacid (TY-51184), or placebo was injected into the abdomen before closing and scores for adhesion formation were assessed at 1, 4, and 12 weeks. A single peritoneal administration of TY-51184 significantly decreased the adhesion scores even at 12 weeks (placebo, 2.80+/-0.20; chymase inhibitor, 1.60+/-0.31). Thus, chymase inhibitors may be a novel strategy to prevent adhesion formation.

Mast cells and oral inflammation

Mast cells are mobile granule-containing secretory cells that are distributed preferentially about the microvascular endothelium in oral mucosa and dental pulp. The enzyme profile of mast cells in oral tissues resembles that of skin, with most mast cells expressing the serine proteases tryptase and chymase. Mast cells in oral tissues contain the pro-inflammatory cytokine tumour necrosis factor-alpha in their granules, and release of this promotes leukocyte infiltration during evolving inflammation in several conditions, including lichen planus, gingivitis, pulpitis, and periapical inflammation, through induction of endothelial-leukocyte adhesion molecules. Mast cell synthesis and release of other mediators exerts potent immunoregulatory effects on other cell types, while several T-lymphocyte-derived cytokines influence mast cell migration and mediator release. Mast cell proteases may contribute to alterations in basement membranes in inflammation in the oral cavity, such as the disruptions that allow cytotoxic lymphocytes to enter the epithelium in oral lichen planus. A close relationship exists among mast cells, neural elements, and laminin, and this explains the preferential distribution of mast cells in tissues. Mast cells are responsive to neuropeptides and, through their interaction with neural elements, form a neural immune network with Langerhans cells in mucosal tissues. This facilitates mast cell degranulation in response to a range of immunological and non-immunological stimuli. Because mast cells play a pivotal role in inflammation, therapies that target mast cell functions could have value in the treatment of chronic inflammatory disorders in the oral cavity.

Conversion of proepithelin to epithelins: roles of SLPI and elastase in host defense and wound repair

Increased leukocyte elastase activity in mice lacking secretory leukocyte protease inhibitor (SLPI) leads to impaired wound healing due to enhanced activity of TGFbeta and perhaps additional mechanisms. Proepithelin (PEPI), an epithelial growth factor, can be converted to epithelins (EPIs) in vivo by unknown mechanisms with unknown consequences. We found that PEPI and EPIs exert opposing activities. EPIs inhibit the growth of epithelial cells but induce them to secrete the neutrophil attractant IL-8, while PEPI blocks neutrophil activation by tumor necrosis factor, preventing release of oxidants and proteases. SLPI and PEPI form complexes, preventing elastase from converting PEPI to EPIs. Supplying PEPI corrects the wound-healing defect in SLPI null mice. Thus, SLPI/elastase act via PEPI/EPIs to operate a switch at the interface between innate immunity and wound healing.

Cardioprotective effects of the serine protease inhibitor aprotinin after regional ischemia and reperfusion on the beating heart

OBJECTIVE

Early coronary reperfusion of the ischemic myocardium is a desired therapeutic goal to preserve myocardium. However, reperfusion itself contributes to an additional myocardial injury (ie, reperfusion injury), which has been attributed to neutrophil infiltration with subsequent release of proteases and oxygen-derived radicals. We studied the effects of the serine protease inhibitor aprotinin (Trasylol) on myocardial ischemia and reperfusion in a rat model.

METHODS

The effects of aprotinin (5000 and 20,000 U/kg) were examined in vivo in a rat model of regional myocardial ischemia (20 minutes) and long-term reperfusion (24 hours). Cardioprotecive effects were determined by means of measurement of creatine kinase and myeloperoxidase activity within the myocardium, as well as histochemical analysis.

RESULTS

Aprotinin (20,000 U/kg) administrated 2 minutes before reperfusion significantly attenuated myocardial injury expressed as creatine kinase washout compared with that seen in vehicle-treated rats (65 +/- 25 vs 585 +/- 98 creatine kinase difference in units per 100 mg, P <.01). Administration of 5000 U/kg of the protease inhibitor resulted in partial inhibition of myocardial reperfusion injury. Moreover, cardiac myeloperoxidase activity in the ischemic myocardium, a marker of neutrophil accumulation, was significantly reduced after aprotinin treatment. Histologic analysis of the reperfused myocardium demonstrated reduced polymorphonuclear leukocyte infiltration and reduced tissue injury. Furthermore, aprotinin treatment resulted in decreased induction of cardiac myocyte apoptosis compared with that seen in vehicle-treated rats.

CONCLUSIONS

Inhibition of serine proteases with aprotinin appears to be an effective means of preserving ischemic myocardium from reperfusion injury, even after 24 hours of reperfusion. Aprotinin might exert cardioprotection through inhibition of polymorphonuclear leukocyte-induced myocardial injury and inhibition of reperfusion-induced apoptosis of cardiac myocytes.

Measurement of free and membrane-bound cathepsin G in human neutrophils using new sensitive fluorogenic substrates

Activated human polymorphonuclear neutrophils at inflammatory sites release the chymotrypsin-like protease cathepsin G, together with elastase and proteinase 3 (myeloblastin), from their azurophil granules. The low activity of cathepsin G on synthetic substrates seriously impairs studies designed to clarify its role in tissue inflammation. We have solved this problem by producing new peptide substrates with intramolecularly quenched fluorescence. These substrates were deduced from the sequence of putative protein targets of cathepsin G, including the reactive loop sequence of serpin inhibitors and the N-terminal domain of the protease-activated receptor of thrombin, PAR-1. Two substrates were selected, Abz-TPFSGQ-EDDnp and Abz-EPFWEDQ-EDDnp, that are cleaved very efficiently by cathepsin G but not by neutrophil elastase or proteinase 3, with specificity constants (k(cat)/K(m)) in the 10(5) M(-1).s(-1) range. They can be used to measure subnanomolar concentrations of free enzyme in vitro and at the surface of neutrophils purified from fresh human blood. Purified neutrophils express 0.02-0.7 pg of cathepsin G/cell (n=15) at their surface. This means that about 10(4) purified cells may be enough to record cathepsin G activity within minutes. This may be most important for investigating the role of cathepsin G as an inflammatory agent, especially in bronchoalveolar lavage fluids from patients with pulmonary inflammatory disorders.

Tissue-specific expression of mast cell granule serine proteinases and their role in inflammation in the lung and gut

Serine proteinases with trypsin-like (tryptase) and chymotrypsin-like (chymase) properties are major constituents of mast cell granules. Several tetrameric tryptases with differing specificities have been characterized in humans, but only a single chymase. In other species there are larger families of chymases with distinct and narrow proteolytic specificities. Expression of chymases and tryptases varies between tissues. Human pulmonary and gastrointestinal mast cells express chymase at lower levels than tryptase, whereas rodent and ruminant gastrointestinal mast cells express uniquely mucosa-specific chymases. Local and systemic release of chymases and tryptases can be quantified by immunoassay, providing highly specific markers of mast cell activation. The expression and constitutive extracellular secretion of the mucosa-specific chymase, mouse mast cell proteinase-1 (mMCP-1), is regulated by transforming growth factor-beta1 (TGF-beta1) in vitro, but it is not clear how the differential expression of chymases and tryptases is regulated in other species. Few native inhibitors have been identified for tryptases but the tetramers dissociate into inactive subunits in the absence of heparin. Chymases are variably inhibited by plasma proteinase inhibitors and by secretory leucocyte protease inhibitor (SLPI) that is expressed in the airways. Tryptases and chymases promote vascular permeability via indirect and possibly direct mechanisms. They contribute to tissue remodelling through selective proteolysis of matrix proteins and through activation of proteinase-activated receptors and of matrix metalloproteinases. Chymase may modulate vascular tissues through its ability to process angiotensin-I to angiotensin-II. Mucosa-specific chymases promote epithelial permeability and are involved in the immune expulsion of intestinal nematodes. Importantly, granule proteinases released extracellularly contribute to the recruitment of inflammatory cells and may thus be involved in innate responses to infection.

Dipeptidyl peptidase I activates neutrophil-derived serine proteases and regulates the development of acute experimental arthritis

Leukocyte recruitment in inflammation is critical for host defense, but excessive accumulation of inflammatory cells can lead to tissue damage. Neutrophil-derived serine proteases (cathepsin G [CG], neutrophil elastase [NE], and proteinase 3 [PR3]) are expressed specifically in mature neutrophils and are thought to play an important role in inflammation. To investigate the role of these proteases in inflammation, we generated a mouse deficient in dipeptidyl peptidase I (DPPI) and established that DPPI is required for the full activation of CG, NE, and PR3. Although DPPI(-/-) mice have normal in vitro neutrophil chemotaxis and in vivo neutrophil accumulation during sterile peritonitis, they are protected against acute arthritis induced by passive transfer of monoclonal antibodies against type II collagen. Specifically, there is no accumulation of neutrophils in the joints of DPPI(-/-) mice. This protective effect correlates with the inactivation of neutrophil-derived serine proteases, since NE(-/-) x CG(-/-) mice are equally resistant to arthritis induction by anti-collagen antibodies. In addition, protease-deficient mice have decreased response to zymosan- and immune complex-mediated inflammation in the subcutaneous air pouch. This defect is accompanied by a decrease in local production of TNF-alpha and IL-1 beta. These results implicate DPPI and polymorphonuclear neutrophil-derived serine proteases in the regulation of cytokine production at sites of inflammation.

Design, synthesis and pharmacological evaluation of 3-benzylazetidine-2-one-based human chymase inhibitors

3-Benzylazetidine-2-one derivatives were designed and evaluated as a novel series of chymase inhibitors. Structure-activity relationship studies of 3-benzylazetidine-2-ones led to compounds 23, which exhibited 3.1 nM inhibition of human chymase and enhancement of stability in human plasma (t(1/2) 6h).

Dipeptidyl peptidase I is essential for activation of mast cell chymases, but not tryptases, in mice

Dipeptidyl peptidase I (DPPI) is the sole activator in vivo of several granule-associated serine proteases of cytotoxic lymphocytes. In vitro, DPPI also activates mast cell chymases and tryptases. To determine whether DPPI is essential for their activation in vivo, we used enzyme histochemical and immunohistochemical approaches and solution-based activity assays to study these enzymes in tissues and bone marrow-derived mast cells (BMMCs) from DPPI +/+ and DPPI -/- mice. We find that DPPI -/- mast cells contain normal amounts of immunoreactive chymases but no chymase activity, indicating that DPPI is essential for chymase activation and suggesting that DPPI -/- mice are functional chymase knockouts. The absence of DPPI and chymase activity does not affect the growth, granularity, or staining characteristics of BMMCs and, despite prior predictions, does not alter IgE-mediated exocytosis of histamine. In contrast, the level of active tryptase (mMCP-6) in DPPI -/- BMMCs is 25% that of DPPI +/- BMMCs. These findings indicate that DPPI is not essential for mMCP-6 activation but does influence the total amount of active mMCP-6 in mast cells and therefore may be an important, but not exclusive mechanism for tryptase activation.

Tryptase-induced airway microvascular leakage in guinea pigs: involvement of tachykinins and leukotrienes

Tryptase, a serine protease synthesized by and stored in mast cells, is implicated as an important mediator in the pathogenesis of airway inflammation. In this study, tryptase was evaluated for its ability to induce microvascular leakage into the airways of guinea pigs. Dose- and time-dependent increases in airway microvascular leakage were produced by intratracheal tryptase (0.3-3 microg). Intratracheal tryptase (3-30 microg) had no effect on airway tone as measured by pulmonary insufflation pressure. Tryptase-induced airway microvascular leakage was partially blocked by the tachykinin NK1 receptor antagonist CP 99994 [(+)-(2S,3S)-3-(2-methoxybenzylamino)-2-phenylpiperidine] and an inhibitor of leukotriene formation SCH 37224 (1-(1,2-dihydro-4-hydroxy-2-oxo-1-phenyl-1,8-naphthyridin-2-yl)pyrrolidinium, hydroxide inner salt). Neither CP 99994 nor SCH 37224 inhibited tryptase proteolytic activity in-vitro. Pretreatment of guinea pigs with histamine H1 receptor antagonists or a tachykinin NK2 receptor antagonist had no affect on the airway microvascular leakage induced by tryptase. It is speculated that tryptase may be important in the pathogenesis of airway inflammation, particularly in disorders that involve increased airway microvascular leakage such as asthma.

Protease activated receptors: theme and variations

The four PAR family members are G protein coupled receptors that are normally activated by proteolytic exposure of an occult tethered ligand. Three of the family members are thrombin receptors. The fourth (PAR2) is not activated by thrombin, but can be activated by other proteases, including trypsin, tryptase and Factor Xa. This review focuses on recent information about the manner in which signaling through these receptors is initiated and terminated, including evidence for inter- as well as intramolecular modes of activation, and continuing efforts to identify additional, biologically-relevant proteases that can activate PAR family members.

Human recombinant pro-dipeptidyl peptidase I (cathepsin C) can be activated by cathepsins L and S but not by autocatalytic processing

Human dipeptidyl peptidase I was expressed in the insect cell/baculovirus system and purified in its active (rhDPPI) and precursor (pro-rhDPPI) forms. RhDPPI was very similar to the purified enzyme (hDPPI) with respect to glycosylation, enzymatic processing, oligomeric structure, CD spectra, and catalytic activity. The precursor, which was a dimer, could be activated approximately 2000-fold with papain. Cathepsin L efficiently activated pro-rhDPPI in vitro at pH 4.5 (k(app) approximately 2 x 10(3) min(-)(1) M(-)(1)), and two cleavage pathways were characterized. The initial cleavage was within the pro region between the residual pro part and the activation peptide. Subsequently, the activation peptide was cleaved from the catalytic region, and the latter was cleaved into the heavy and light chains. Alternatively, the pro region was first separated from the catalytic region. Cathepsin S was a less efficient activating enzyme. Cathepsin B and rhDPPI did not activate pro-rhDPPI, and the proenzyme was incapable of autoactivation. Incubation of both pro-rhDPPI and rhDPPI with cathepsin D resulted in degradation. Cystatin C and stefins A and B inhibited rhDPPI with K(i) values in the nanomolar range (K(i) = 0.5-1.1 nM). The results suggest that cathepsin L could be an important activator of DPPI in vivo and that cathepsin D and possibly the cystatins may contribute to DPPI downregulation.

Synthesis and structure-activity relationships of a new class of 1-oxacephem-based human chymase inhibitors

1-Oxacephem derivatives were synthesized and evaluated as a novel series of chymase inhibitors. Structure-activity relationship studies of 1-oxacephems led to compound 34, which exhibited 6 nM inhibition of human chymase and high selectivity for human chymase compared to other serine enzymes.

Suppressed smooth muscle proliferation and inflammatory cell invasion after arterial injury in elafin-overexpressing mice

Elastases degrade the extracellular matrix, releasing growth factors and chemotactic peptides, inducing glycoproteins such as tenascin, and thereby promoting vascular cell proliferation and migration. Administration of serine elastase inhibitors reduces experimentally induced vascular disease. The ability to mount an intrinsic anti-elastase response may, therefore, protect against intimal/medial thickening after vascular injury. To investigate this, we showed that wire-induced endothelial denudation of the carotid artery is associated with transient elevation in elastase activity and confirmed that this is abolished in transgenic mice overexpressing the serine elastase inhibitor, elafin, targeted to the cardiovascular system. Ten days after injury, nontransgenic littermates show vessel enlargement, intimal thickening, increased medial area and cellularity, and 2-fold increase in tenascin. Injured vessels in transgenic mice become enlarged but are otherwise similar to sham-operated controls. Injury-induced vessel wall thickening, which is observed only in nontransgenic mice, is related to foci of neutrophils and macrophages, in addition to smooth muscle cells that fail to stain for alpha-actin and are likely dedifferentiated. Our study therefore suggests that a major determinant of the vascular response to injury is the early transient induction of serine elastase activity, which leads to cellular proliferation and inflammatory cell migration.

Utilization of the 1,2,5-thiadiazolidin-3-one 1,1 dioxide scaffold in the design of potent inhibitors of serine proteases: SAR studies using carboxylates

A series of carboxylate derivatives based on the 1,2,5-thiadiazolidin-3-one 1,1 dioxide and isothiazolidin-3-one 1,1 dioxide scaffolds has been synthesized and the inhibitory profile of these compounds toward human leukocyte elastase (HLE), cathepsin G (Cat G) and proteinase 3 (PR 3) was then determined. Most of the compounds were found to be potent, time-dependent inhibitors of elastase, with some of the compounds exhibiting k(inact)/K1 values as high as 4,928,300 M(-1) s(-1). The inhibitory potency of carboxylate derivatives based on the 1,2,5-thiadiazolidin-3-one 1,1 dioxide platform was found to be influenced by both the pKa and the inherent structure of the leaving group. Proper selection of the primary specificity group (R(I)) was found to lead to selective inhibition of HLE over Cat G, however, those compounds that inhibited HLE also inhibited PR 3, albeit less efficiently. The predictable mode of binding of these compounds suggests that, among closely-related serine proteases, highly selective inhibitors of a particular serine protease can be fashioned by exploiting subtle differences in their S' subsites. This study has also demonstrated that the degradative action of elastase on elastin can be abrogated in the presence of inhibitor 17.

Human chymase inhibitors based on the 1,2,5-thiadiazolidin-3-one 1,1 dioxide scaffold

A series of compounds that utilize the 1,2,5-thiadiazolidin-3-one 1,1 dioxide scaffold was synthesized and shown to be highly effective inhibitors of recombinant human skin chymase.

The Intracellular Serpin Proteinase Inhibitor 6 Is Expressed in Monocytes and Granulocytes and Is a Potent Inhibitor of the Azurophilic Granule Protease, Cathepsin G

The monocyte and granulocyte azurophilic granule proteinases elastase, proteinase 3, and cathepsin G are implicated in acute and chronic diseases thought to result from an imbalance between the secreted proteinase(s) and circulating serpins such as 1-proteinase inhibitor and 1-antichymotrypsin. We show here that the intracellular serpin, proteinase inhibitor 6 (PI-6), is present in monocytes, granulocytes, and myelomonocytic cell lines. In extracts from these cells, PI-6 bound an endogenous membrane-associated serine proteinase to form an sodium dodecyl sulfate (SDS)-stable complex. Using antibodies to urokinase, elastase, proteinase 3, or cathepsin G, we demonstrated that the complex contains cathepsin G. Native cathepsin G and recombinant PI-6 formed an SDS-stable complex in vitro similar in size to that observed in the extracts. Further kinetic analysis demonstrated that cathepsin G and PI-6 rapidly form a tight 1:1 complex (ka = 6.8 ± 0.2 × 106mol/L−1s−1 at 17°C;Ki = 9.2 ± 0.04 × 10−10 mol/L). We propose that PI-6 complements 1-proteinase inhibitor and 1-antichymotrypsin (which control extracellular proteolysis) by neutralizing cathepsin G that leaks into the cytoplasm of monocytes or granulocytes during biosynthesis or phagocytosis. Control of intracellular cathepsin G may be particularly important, because it has recently been shown to activate the proapoptotic proteinase, caspase-7.

Regulation of pro-apoptotic leucocyte granule serine proteinases by intracellular serpins

Caspase activation and apoptosis can be initiated by the introduction of serine proteinases into the cytoplasm of a cell. Cytotoxic lymphocytes have evolved at least one serine proteinase with specific pro-apoptotic activity (granzyme B), as well as the mechanisms to deliver it into a target cell, and recent evidence suggests that other leucocyte granule proteinases may also have the capacity to kill if released into the interior of cells. For example, the monocyte/granulocyte proteinase cathepsin G can activate caspases in vitro, and will induce apoptosis if its entry into cells is mediated by a bacterial pore-forming protein. The potent pro-apoptotic activity of granzyme B and cathepsin G suggests that cells producing these (or other) proteinases would be at risk from self-induced death if the systems involved in packaging, degranulation or targeting fail and allow proteinases to enter the host cell cytoplasm. The purpose of the present review is to describe recent work on a group of intracellular serine proteinase inhibitors (serpins) which may function in leucocytes to prevent autolysis induced by the granule serine proteinases.

Elastase in hyperpnea-induced guinea pig airway constriction

Aerosolized elastase has been shown to produce airway constriction in guinea pigs. In this study, we examined whether endogenous elastase plays a role in isocapnic hyperpnea-induced airway constriction using an elastase inhibitor, eglin-c. The study was divided into three experiments. In the first experiment, we used an elastase inhibitor, eglin-c, to suppress hyperpnea-induced bronchoconstriction. Twenty-two young male Hartley guinea pigs were divided into three groups: control (n=8), eglin-c(1) (a lower dose of eglin-c, n=7), and eglin-c(2) (a higher dose of eglin-c, n=7). In the second experiment, we tested whether eglin-c affects pulmonary function following 15 min of normal air ventilation in two groups of animals: control (n=8) and eglin-c (n=8). In the third experiment, animals were divided into two groups: control (n=7) and compound 48/80 (a mast cell degranulating agent, n=7). Airway function was examined in the anesthetized-paralyzed animal. In the first and third experiments, 15 min of isocapnic hyperpnea caused marked decreases in dynamic respiratory compliance, forced expiratory flow at 0.1 s and maximal expiratory flow at 50% total lung capacity, demonstrating hyperpnea-induced airway constriction. This bronchoconstriction was significantly attenuated by eglin-c and by pretreatment with compound 48/80. In the second experiment, eglin-c did not significantly affect bronchial function following normal air ventilation. These data suggest that elastase released from mast cells directly or indirectly induces hyperpnea-induced bronchoconstriction.

Fibroproliferation and mast cells in the acute respiratory distress syndrome

BACKGROUND

Mast cells (MCs), which are a major source of cytokines and growth factors, have been implicated in various fibrotic disorders. To clarify the contribution of MCs to fibrogenesis, lung tissue from patients with the acute respiratory distress syndrome (ARDS) was examined during exudative through to fibroproliferative stages.

METHODS

Lung tissue was obtained from 17 patients with ARDS who had pathological features of the early exudative stage (n = 6) or the later reparative stages (n = 11), from four patients with idiopathic pulmonary fibrosis, and from three patients with normal lung tissue. Immunohistochemical localisation of tryptase (found in all human MCs), chymase (found in a subset of human MCs), alpha-smooth muscle actin (identifies myofibroblasts), and procollagen type I was performed.

RESULTS

Normal lung tissue exhibited myofibroblast and procollagen type I immunolocalisation scores each of < 5 and MC scores of 1. Increased scores were defined as myofibroblast and procollagen type I scores of > 10 and MC scores of > or = 2. Eighty percent of lung tissue samples from the early exudative stage of ARDS exhibited increased numbers of myofibroblasts, 50% had increased numbers of procollagen type I producing cells, while only 17% had increased numbers of MCs compared with control samples. All samples from the later reparative stages of ARDS had increased numbers of myofibroblasts and procollagen type I producing cells. Increased numbers of MCs were seen in 55% of samples from the reparative stages. There was no significant shift in MC phenotype in the ARDS samples.

CONCLUSIONS

Increased numbers of myofibroblasts and procollagen type I producing cells were frequently found early in the course of ARDS. MC hyperplasia was unusual during this stage, but was often a feature of the later reparative stages. MCs do not appear to initiate fibroproliferation in ARDS.

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.

Studies on 2-benzyloxy-4H-3,1-benzoxazin-4-ones as serine protease inhibitors

The class of 3,1-benzoxazin-4-ones includes potent inhibitors of various serine proteases. Structural investigation on three 2-benzyloxy-4H-3,1-benzoxazin-4-ones (1-3) are described with respect to their reactivity to alkaline hydrolysis. The 13C NMR data of 2-benzyloxy-5-methyl-4H-3,1-benzoxazin-4-one 3 are discussed. This peri substituted compound was subjected to a crystal structure analysis. The heterocyclic skeleton together with the carbonyl oxygen and the methyl carbon is planar, and only small angle distortions occurred. The inhibition of neutrophil serine proteases by 1-3 is reported. The different reactivity of the 5-methyl derivative 3 towards serine proteases is mainly influenced by specific interactions within the active sites. Thus, 3 was found to rapidly acylate human leukocyte proteinase 3 and exhibited a Ki value of 1.8 nM.

Cloning and characterization of the cDNA for human airway trypsin-like protease

Previously we isolated a trypsin-like enzyme designated human airway trypsin-like protease from the sputum of patients with chronic airway diseases. This paper describes the cDNA cloning, characterization of the primary protein structure deduced from the cDNA, and gene expression of this enzyme in various human tissues. We obtained an entire 1517-base pair sequence of cDNA with an open reading frame encoding a polypeptide with 418-amino acid residues. The polypeptide consisted of a 232-residue catalytic region and a 186-residue noncatalytic region with a hydrophobic putative transmembrane domain near the NH2 terminus. The polypeptide was suggested to be a type II integral membrane protein in which the COOH-terminal catalytic region is extracellular. Therefore, this protein is thought to be synthesized as a membrane-bound precursor and to mature to a soluble and active protease by limited proteolysis. It showed 29-38% identity in the sequence of the catalytic region with human hepsin, enteropeptidase, acrosin, and mast cell tryptase. The noncatalytic region had little similarity to other known proteins. In Northern blot analysis a transcript of 1.9 kilobases was detectable most prominently in the trachea among 17 human tissues examined.

Activities of proteases in parietal thrombus of aortic aneurysm

Deterioration of the aortic wall resulting in formation of aneurysm may be evoked by increased activity of elastases, collagenases and lysosomal proteases. These enzymes come from macrophages and neutrophil granulocytes which are elements of the inflammatory reaction accompanying aneurysm. These cells may also come from parietal thrombus in the aneurysm lumen. The aim of this work was to determine activity of elastase, cathepsin G, collagenase-like Pz-peptidase and cathepsins A, B, C, D and E in the parietal thrombus of aortic aneurysm. The thrombus was obtained from the lumen of the aortic aneurysm of six patients during operation. Protease activities were determined using specific substrates at optimum pH. Retracted blood clot was a comparative material. The thrombus of aortic aneurysm showed two-five fold higher activity of elastases, collagenase-like Pz-peptidase and cathepsins A, D and G in comparison to the blood clot (P < 0.001). However, activity of cathepsins B, C and E in the thrombus was only slightly higher (P < 0.05). Prolonged effect of proteases coming from parietal thrombus on the aneurysm wall could evoke marked degradation of fibrillar proteins resulting in increase of aneurysm.