Human neutrophil collagenase cleaves alpha 1-antitrypsin

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

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

The Role of Neutrophils and Neutrophil Elastase in Pneumococcal Pneumonia

Streptococcus pneumoniae, also known as pneumococcus, is a Gram-positive diplococcus and a major human pathogen. This bacterium is a leading cause of bacterial pneumonia, otitis media, meningitis, and septicemia, and is a major cause of morbidity and mortality worldwide. To date, studies on S. pneumoniae have mainly focused on the role of its virulence factors including toxins, cell surface proteins, and capsules. However, accumulating evidence indicates that in addition to these studies, knowledge of host factors and host-pathogen interactions is essential for understanding the pathogenesis of pneumococcal diseases. Recent studies have demonstrated that neutrophil accumulation, which is generally considered to play a critical role in host defense during bacterial infections, can significantly contribute to lung injury and immune subversion, leading to pneumococcal invasion of the bloodstream. Here, we review bacterial and host factors, focusing on the role of neutrophils and their elastase, which contribute to the progression of pneumococcal pneumonia.

Proteolytic cleavage of HLA class II by human neutrophil elastase in pneumococcal pneumonia

Bacterial and viral respiratory infections can initiate acute lung injury and acute respiratory distress syndrome. Neutrophils and their granule enzymes, including neutrophil elastase, are key mediators of the pathophysiology of acute respiratory failure. Although intracellular neutrophil elastase functions as a host defensive factor against pathogens, its leakage into airway spaces induces degradation of host connective tissue components. This leakage disrupts host innate immune responses via proteolytic cleavage of Toll-like receptors and cytokines. Here, we investigated whether neutrophils possess proteases that cleave adaptive immune molecules. We found that expression of the human leukocyte antigen (HLA) class II molecule HLA-DP β1 was decreased in THP-1-derived macrophages treated with supernatants from dead neutrophils. This decreased HLA-DP β1 expression was counteracted by treatment with neutrophil elastase inhibitor, suggesting proteolytic cleavage of HLA-DP β1 by neutrophil elastase. SDS-PAGE showed that neutrophil elastase cleaved recombinant HLA-DP α1, -DP β1, -DQ α1, -DQ β1, -DR α, and -DR β1. Neutrophil elastase also cleaved HLA-DP β1 on extracellular vesicles isolated from macrophages without triggering morphological changes. Thus, leakage of neutrophil elastase may disrupt innate immune responses, antigen presentation, and T cell activation. Additionally, inhibition of neutrophil elastase is a potential therapeutic option for treating bacterial and viral pneumonia.

Neutrophil elastase and endogenous inhibitors in Behçet's disease saliva

Behçet's disease (BD) is a vasculitis of unknown aetiology typified by chronic recurrent oral ulcers and systemic inflammatory manifestations. Neutrophils, and specifically their protease neutrophil elastase (NE), have been implicated in its pathology. Although NE is an effective anti-microbial, excessive NE can damage host tissue. Recurrent oral ulceration is a primary BD symptom, therefore we hypothesized that excessive neutrophil infiltration evidenced by increased NE and a reduction in specific endogenous inhibitors, secretory leucocyte protease inhibitor (SLPI) and alpha1-anti-trypsin (α1AT) contributes to BD mucosal instability. NE, SLPI and α1AT were quantified in saliva from BD patients with active oral ulcers (BDa) and quiet without ulcers (BDq), recurrent aphthous stomatitis (RASa; RASq) and healthy controls (HC). Although BDq saliva had marginally higher median NE levels (1112 ng/ml) compared to both RASq (1043 ng/ml) and HC (999 ng/ml), SLPI was significantly reduced in BDq (P < 0·01). Despite decreased SLPI protein, mRNA expression was significantly increased in BDq buccal epithelial swabs compared to RASq and HC (P < 0·05, P < 0·001). NE remained enzymatically active, although α1AT levels were at least eight times higher than SLPI in all groups, suggesting that α1AT does not have a primary role in counteracting NE in saliva. Furthermore, NE levels in BDa patients medicated with both azathioprine (AZA) and colchicine (COLC) were significantly lower than those on COLC (P = 0·0008) or neither (P = 0·02), indicating that combining AZA + COLC may help to regulate excessive NE during ulceration. This study showed that enzymatically active NE coupled with reduced SLPI in BD saliva may contribute to recurrent oral ulcerations.

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.

The Role of Serine Proteases and Antiproteases in the Cystic Fibrosis Lung

Cystic fibrosis (CF) lung disease is an inherited condition with an incidence rate of approximately 1 in 2500 new born babies. CF is characterized as chronic infection of the lung which leads to inflammation of the airway. Sputum from CF patients contains elevated levels of neutrophils and subsequently elevated levels of neutrophil serine proteases. In a healthy individual these proteases aid in the phagocytic process by degrading microbial peptides and are kept in homeostatic balance by cognate antiproteases. Due to the heavy neutrophil burden associated with CF the high concentration of neutrophil derived proteases overwhelms cognate antiproteases. The general effects of this protease/antiprotease imbalance are impaired mucus clearance, increased and self-perpetuating inflammation, and impaired immune responses and tissue. To restore this balance antiproteases have been suggested as potential therapeutics or therapeutic targets. As such a number of both endogenous and synthetic antiproteases have been trialed with mixed success as therapeutics for CF lung disease.

Systemic anti-microbial agents used in periodontal therapy

Periodontitis is an infectious disease with marked inflammatory response, leading to destruction of underlying tissues. The aim of periodontal therapy is to eradicate the pathogens associated with the disease and attain periodontal health. This is achieved by non-surgical and surgical therapy; however, mechanical debridement and topical application of antiseptics may not be helpful in all cases. In such cases, adjunctive systemic antibiotic therapy remains the treatment of choice. It can reach micro-organisms at the base of the deep periodontal pockets and furcation areas via serum, and also affect organisms residing within gingival epithelium and connective tissue. Before advising any anti-microbial agent, it is necessary to have knowledge of that agent. The aim of this review article is to provide basic details of each systemic anti-microbial agent used in periodontal therapy. The points discussed are its mode of action, susceptible periodontal pathogens, dosage, its use in treatment of periodontal disease, and mechanism of bacterial resistance to each anti-microbial agent. It might be of some help while prescribing these drugs.

Surveying proteolytic processes in human cancer microenvironments by microdialysis and activity-based mass spectrometry

PURPOSE

We present a strategy to survey proteolytic processes that occur in human cancer microenvironments.

EXPERIMENTAL DESIGN

In situ microdialysis during oral cancer surgery was combined with mass spectrometry-based proteomics to analyze interstitial fluid surrounding tumors and anatomically matched normal sites. Protease activity-based (18)O-profiling was utilized to reveal peptides that were processed by co-collected proteases ex vivo.

RESULTS

We demonstrated for the first time the use of microdialysis in humans to collect interstitial fluid from cancer microenvironments. Proteomic profiling identified proteases and inhibitors in the microdialysis samples. A subset of peptides displayed characteristic (18)O-isotope patterns that indicated processing by endogenous proteases.

CONCLUSIONS AND CLINICAL RELEVANCE

The presented approach provides unprecedented views of in vivo targets of proteases without disrupting the cancer or surrounding tissue. The methodology can be broadly adapted to other physiological conditions in which proteolytic mediators are involved (e.g. arthritic joints, inflamed muscle, other types of cancer) and where a comparison of normal and pathological tissue is sought.

Neutrophil elastase, proteinase 3, and cathepsin G as therapeutic targets in human diseases

Polymorphonuclear neutrophils are the first cells recruited to inflammatory sites and form the earliest line of defense against invading microorganisms. Neutrophil elastase, proteinase 3, and cathepsin G are three hematopoietic serine proteases stored in large quantities in neutrophil cytoplasmic azurophilic granules. They act in combination with reactive oxygen species to help degrade engulfed microorganisms inside phagolysosomes. These proteases are also externalized in an active form during neutrophil activation at inflammatory sites, thus contributing to the regulation of inflammatory and immune responses. As multifunctional proteases, they also play a regulatory role in noninfectious inflammatory diseases. Mutations in the ELA2/ELANE gene, encoding neutrophil elastase, are the cause of human congenital neutropenia. Neutrophil membrane-bound proteinase 3 serves as an autoantigen in Wegener granulomatosis, a systemic autoimmune vasculitis. All three proteases are affected by mutations of the gene (CTSC) encoding dipeptidyl peptidase I, a protease required for activation of their proform before storage in cytoplasmic granules. Mutations of CTSC cause Papillon-Lefèvre syndrome. Because of their roles in host defense and disease, elastase, proteinase 3, and cathepsin G are of interest as potential therapeutic targets. In this review, we describe the physicochemical functions of these proteases, toward a goal of better delineating their role in human diseases and identifying new therapeutic strategies based on the modulation of their bioavailability and activity. We also describe how nonhuman primate experimental models could assist with testing the efficacy of proposed therapeutic strategies.

Tetracycline compounds with non-antimicrobial organ protective properties: possible mechanisms of action

Tetracyclines were developed as a result of the screening of soil samples for antibiotics. The first^t of these compounds, chlortetracycline, was introduced in 1947. Tetracyclines were found to be highly effective against various pathogens including rickettsiae, as well as both gram-positive and gram-negative bacteria, thus becoming the first class of broad-spectrum antibiotics. Many other interesting properties, unrelated to their antibiotic activity, have been identified for tetracyclines which have led to widely divergent experimental and clinical uses. For example, tetracyclines are also an effective anti-malarial drug. Minocycline, which can readily cross cell membranes, is known to be a potent anti-apoptotic agent. Another tetracycline, doxycycline is known to exert anti-protease activities. Doxycycline can inhibit matrix metalloproteinases which contribute to tissue destruction activities in diseases such as periodontitis. A large body of literature has provided additional evidence for the “beneficial” actions of tetracyclines, including their ability to act as reactive oxygen species scavengers and anti-inflammatory agents. This review provides a summary of tetracycline's multiple mechanisms of action as a means to understand their beneficial effects.

Functional study of elafin cleaved by Pseudomonas aeruginosa metalloproteinases

Elafin is a 6-kDa innate immune protein present at several epithelial surfaces including the pulmonary epithelium. It is a canonical protease inhibitor of two neutrophil serine proteases [neutrophil elastase (NE) and proteinase 3] with the capacity to covalently bind extracellular matrix proteins by transglutamination. In addition to these properties, elafin also possesses antimicrobial and immunomodulatory activities. The aim of the present study was to investigate the effect of Pseudomonas aeruginosa proteases on elafin function. We found that P. aeruginosa PAO1-conditioned medium and two purified Pseudomonas metalloproteases, pseudolysin (elastase) and aeruginolysin (alkaline protease), are able to cleave recombinant elafin. Pseudolysin was shown to inactivate the anti-NE activity of elafin by cleaving its protease-binding loop. Interestingly, antibacterial properties of elafin against PAO1 were found to be unaffected after pseudolysin treatment. In contrast to pseudolysin, aeruginolysin failed to inactivate the inhibitory properties of elafin against NE. Aeruginolysin cleaves elafin at the amino-terminal Lys6-Gly7 peptide bond, resulting in a decreased ability to covalently bind purified fibronectin following transglutaminase activity. In conclusion, this study provides evidence that elafin is susceptible to proteolytic cleavage at alternative sites by P. aeruginosa metalloproteinases, which can affect different biological functions of elafin.

Tetracyclines: a pleitropic family of compounds with promising therapeutic properties. Review of the literature

There must be something unique about a class of drugs (discovered and developed in the mid-1940s) where there are more than 130 ongoing clinical trials currently listed. Tetracyclines were developed as a result of the screening of soil samples for antibiotic organisms. The first of these compounds chlortetracycline was introduced in 1948. Soon after their development tetracyclines were found to be highly effective against various pathogens including rickettsiae, Gram-positive, and Gram-negative bacteria, thus, becoming a class of broad-spectrum antibiotics. The mechanism of action of tetracyclines is thought to be related to the inhibition of protein synthesis by binding to the 30S bacterial ribosome. Tetracyclines are also an effective anti-malarial drug. Over time, many other "protective" actions have been described for tetracyclines. Minocycline, which can readily cross cell membranes, is known to be a potent anti-apoptotic agent. Its mechanism of action appears to relate to specific effects exerted on apoptosis signaling pathways. Another tetracycline, doxycycline is known to exert antiprotease activities. Doxycycline can inhibit matrix metalloproteinases, which contribute to tissue destruction activities in diseases such as gingivitis. A large body of literature has provided additional evidence for the "beneficial" actions of tetracyclines, including their ability to act as oxygen radical scavengers and anti-inflammatory agents. This increasing volume of published work and ongoing clinical trials supports the notion that a more systematic examination of their possible therapeutic uses is warranted. This review provides a summary of tetracycline's multiple mechanisms of action and while using the effects on the heart as an example, this review also notes their potential to benefit patients suffering from various pathologies such as cancer, Rosacea, and Parkinson's disease.

Matrix metalloproteinase-8 deficiency promotes granulocytic allergen-induced airway inflammation

Matrix metalloproteinases (MMPs) are involved in inflammatory reaction, including asthma-related airway inflammation. MMP-8, mainly produced by neutrophils, has recently been reported to be increased in the bronchoalveolar lavage fluid (BALF) from asthmatic patients. To evaluate the role of MMP-8 in asthma, we measured MMP-8 expression in lung tissue in an OVA-sensitized mouse model of asthma and addressed the effect of MMP-8 deletion on allergen-induced bronchial inflammation. MMP-8 production was increased in lungs from C57BL/6 mice exposed to allergens. After allergen exposure, MMP-8(-/-) mice developed an airway inflammation characterized by an increased neutrophilic inflammation in BALF and an increased neutrophilic and eosinophilic infiltration in the airway walls. MMP-8 deficiency was associated with increased levels of IL-4 and anti-OVA IgE and IgG1 in BALF and serum, respectively. Although allergen exposure induced an enhancement of LPS-induced CXC chemokine, KC, and MIP-2 levels in BALF and lung parenchyma, no difference was observed between the two genotypes. Inflammatory cell apoptosis was reduced in the lungs from MMP-8(-/-) mice. For the first time, our study evidences an important role of MMP-8 in the control of neutrophilic and eosinophilic infiltration during allergen-induced lung inflammation, and demonstrates that the anti-inflammatory effect of MMP-8 is partly due to a regulation of inflammatory cell apoptosis.

Human mesenchymal stem cell derived osteoblasts degrade organic bone matrix in vitro by matrix metalloproteinases

Some recent studies have suggested that cells of mesenchymal origin might participate in the organic bone matrix dissolution. In the present study, collagen synthesis and degradation by human mesenchymal stem cell (MSC) derived cells were studied at early stage of osteoblast differentiation using a special two-stage in vitro culture model. In this model, cells were cultured on bovine bone slices, which were first resorbed by osteoclasts. Synthesis of type I collagen was markedly enhanced when mesenchymal cells were cultured on bone matrix. After thorough osteoclast removal, MSC derived cells were capable of degrading the organic bone matrix, and caused a release of type I collagen degradation product (ICTP) into the culture medium. This was inhibited by matrix metalloproteinase (MMP) inhibitor, while cysteine proteinase inhibitor or estrogen had no inhibitory effect. Western blot analysis or gelatin zymography confirmed the presence of MMP-2, -8, -13 and -14, but not MMP-1 or -9, in the differentiated cells. 17beta-Estradiol was found to increase the expression of MMP-2 and -14 by these cells. Finally, scanning electron microscopy showed that the differentiating human MSCs were capable of degrading organic bone matrix remnants from the bottom of the resorption lacunae. These data support the hypothesis that collagen cleavage by the same cells that are subsequently responsible for bone formation is MMP mediated process and is an important step coupling bone formation into bone resorption.

Divergent effects of alpha1-antitrypsin on neutrophil activation, in vitro

alpha1-Antitrypsin (AAT) is a major circulating serine proteinase inhibitor in humans. The anti-proteinase activity of AAT is inhibited by chemical modification. These include inter- or intramolecular polymerisation, oxidation, complex formation with target proteinases (e.g., neutrophil elastase), and/or cleavage by multi-specific proteinases. In vivo, several modified forms of AAT have been identified which stimulate biological activity in vitro unrelated to inhibition of serine proteinases. In this study we have examined the effects of native and polymerised AAT and C-36 peptide, a proteolytic cleavage product of AAT, on human neutrophil activation, in vitro. We show that the C-36 peptide displays striking concentration-dependent pro-inflammatory effects on human neutrophils, including induction of neutrophil chemotaxis, adhesion, degranulation, and superoxide generation. In contrast to C-36 peptide, native and polymerised AAT at similar and higher concentrations showed no effects on neutrophil activation. These results suggest that cleavage of AAT may not only abolish its proteinase inhibitor activity, but can also generate a powerful pro-inflammatory activator for human neutrophils.

Tumor-associated trypsinogen-2 (trypsinogen-2) activates procollagenases (MMP-1, -8, -13) and stromelysin-1 (MMP-3) and degrades type I collagen

A critical step in cancer growth and metastasis is the dissolution of the extracellular matrix surrounding the malignant tumor, which leads to tumor cell invasion and dissemination. Type I collagen degradation involves the initial action of collagenolytic matrix metalloproteinases (MMP-1, -8, and -13) activated by MMP-3 (stromelysin-1). The role of interactive matrix serine proteinases (MSPs), including tumor-associated trypsinogens, has been unclear in collagenolysis. Now, we provide evidence that the major isoenzyme of human tumor-associated trypsinogens, trypsin-2, can directly activate three collagenolytic proMMPs as well as proMMP-3. These proMMP activations are inhibited by tumor-associated trypsin inhibitor (TATI). Furthermore, we demonstrate that trypsin-2 efficiently degrades native soluble type I collagen, which can be inhibited by TATI. However, cell culture studies showed that trypsin-2 transfection into the HSC-3 cell line did not result in MMP-1, -3, -8, and -13 activation but affected MMP-3 and -8 production at the protein level. These findings indicate that human trypsin-2 can be regarded as a potent tumor-associated matrix serine protease capable of being the initial activator of the collagenolytic MMP activation network as well as directly attacking type I collagen.

Inhibition of collagenase and metalloproteinases by aloins and aloe gel

The effects of Aloe barbadensis gel and aloe gel constituents on the activity of microbial and human metalloproteinases have been investigated. Clostridium histolyticum collagenase (ChC) results dose-dependently inhibited by aloe gel and the activity-guided fractionation led to an active fraction enriched in phenolics and aloins. Aloins have been shown to be able to bind and to inhibit ChC reversibly and non-competitively. Aloe gel and aloins are also effective inhibitors of stimulated granulocyte matrix metalloproteinases (MMPs). The remarkable structural resemblances between aloins and the pharmacophore structure of inhibitory tetracyclines, suggest that the inhibitory effects of aloins are via an interaction between the carbonyl group at C(9) and an adjacent hydroxyl group of anthrone (C(1) or C(8)) at the secondary binding site of enzyme, destabilizing the structure of granulocyte MMPs.

Airway obstruction correlates with collagenase-2 (MMP-8) expression and activation in bronchial asthma

Matrix metalloproteinases (MMPs) contribute to extracellular matrix and basement membrane degradation in asthma. The present study analyzed molecular forms and degree of activation and expression of MMP-8 in bronchoalveolar lavage fluid (BALF), BALF cells, and bronchial tissue specimens from 14 steroid-naive asthma patients, 13 uncontrolled severe asthma patients, 13 controlled asthma patients, and 14 healthy subjects by Western immunoblotting, immunohistochemistry, and in situ hybridization. Immunohistochemistry and in situ hybridization revealed a prominent MMP-8 immunoreactivity in submucosal inflammatory, glandular, and shed, but not in intact bronchial epithelial cells of asthma patients. In BALF cytospins, both MMP-8 protein and mRNA expression were observed in epithelial cells, macrophages, and polymorphonuclear leukocytes (PMNs). MMP-8 was present in BALFs asthma patients in complex, pro- and active PMN-type, and pro- and active non-PMN-type forms. BALF MMP-8 was significantly converted to active form only in BALFs from steroid-naive and uncontrolled severe asthma patients, but not in BALFs from well-controlled asthma patients or healthy controls. A significant inverse correlation between BALF MMP-8 levels and FEV1 (r = -0.283, p = 0.04), and BALF activated MMP-8 forms and FEV1 (r = -0.427, p = 0.001) was detected. Overall, these data suggest that MMP-8 and its activation has an important role in the airway destruction, healing, remodeling, and treatment response in asthma.

Inflammation. 2: Its role in the healing of chronic wounds

Why do some wounds fail to heal in the expected time? Part two of this article on inflammation discusses the possible causes, which include recurrence of trauma, bacterial and other contamination and perhaps, above all, the ageing process.

Expression and regulation of collagenase-2 (MMP-8) in head and neck squamous cell carcinomas

MMP-8 (collagenase-2) is the most effective collagenase to initiate type I collagen degradation. Since initiation of lysis of the surrounding collagen matrix is an essential prerequisite for carcinoma cells to spread, this study investigated the expression of MMP-8 in squamous cell carcinoma (SCC) of the head and neck in vivo and in vitro. Most of the recently established head and neck carcinoma cell lines (22/25), corresponding tumour (5/7) and dermal (2/2) fibroblasts, commercial tongue carcinoma (HSC-3 and SCC-25), and transformed keratinocyte cell lines of the tongue (IHGK) and skin (HaCaT) expressed MMP-8 mRNA analysed by the PCR method. Western blotting revealed a latent 50 kD band in concentrated culture media of carcinoma cells and corresponding tumour and dermal fibroblasts. The expression of immunoreactive MMP-8 protein was reduced 30% by transforming growth factor beta-1 (TGF-beta1) at 1 ng/ml concentration and 60% at 10 ng/ml concentration, but up-regulated 2- and 2.5-fold after 10 nM and 100 nM phorbol 12-myristate 13 acetate (PMA), respectively. Immunohistological staining localized MMP-8 protein in a few malignant invading tumour cell islands, certain fibroblasts, polymorphonuclear neutrophils (PMNs), and plasma cells. In situ hybridization revealed a faint sporadic signal in carcinoma cells of all eight tissue sections analysed. It is concluded that tissue from head and neck carcinomas can express MMP-8 both in vivo and in vitro. Since the amount of MMP-8 in carcinoma and stromal cells is rather low, MMP-8 may have a potential role, with other collagenases, in the proteolysis of connective tissue associated with the spreading of invasive carcinoma.

C-terminal fragment of alpha1-antitrypsin activates human monocytes to a pro-inflammatory state through interactions with the CD36 scavenger receptor and LDL receptor

Monocyte scavenger receptor, CD36 has been implicated in the pathogenesis of atherosclerosis as a major oxidised LDL receptor mediating lipid accumulation and foam cell formation. Previously, we found that treatment of monocyte cultures with the carboxyl terminal fragment of alpha1-antitrypsin (C-36) increases lipid binding and uptake, induces LDL receptor mRNA and CD36 receptor protein expression, and also significantly increases production of pro-inflammatory molecules. To assess the role of the CD36 receptor in proatherogenic monocyte activation by the C-36 fragment, we tested whether specific anti-CD36 receptor antibodies would block the effects of C-36 on monocyte activation. We find that pre-incubation of cells with anti-LDL and anti-CD36 receptor antibodies (10 microg/ml) blocks binding of 125I-C-36 by about 50%. Similarly, cells pre-incubated with oxidised LDL or native LDL at concentrations from 2.5 to 10 microg/ml showed a loss of 125I-C-36 binding (up to 49 and 57%) and uptake (up to 47 and 59.8%), respectively. In parallel experiments, monocytes were first incubated for 1 or 6 h with anti-CD36 antibodies (10 microg/ml) prior to adding C-36 peptide. Anti-CD36 antibodies suppressed C-36-induced production of gelatinase B, monocyte chemoattractant protein-1, interleukin-6 and cellular oxygen consumption to control levels, whereas levels of TNFalpha were unaffected. In contrast, saturation of LDL receptors with excess of anti-LDL (20 microg/ml) significantly inhibited C-36 induced TNFalpha levels. Results indicate that the C-36 peptide binds to both LDL and CD36 scavenger receptors which involves selective upregulation of pro-inflammatory molecules and activation of the respiratory burst in human monocytes. This also supports important roles for CD36 and LDL receptors in atherogenesis and suggests that blockade of CD36 receptor can be protective in pro-inflammatory activation of human monocytes.

Evaluation of collagenase activity, matrix metalloproteinase-8, and matrix metalloproteinase-13 in horses with chronic obstructive pulmonary disease

OBJECTIVES

To determine collagenase activity and evaluate matrix metalloproteinase (MMP)-8 and MMP-13 in horses with chronic obstructive pulmonary disease (COPD).

ANIMALS

12 horses with COPD and 12 healthy control horses.

PROCEDURE

Collagenase activity was determined by use of an assay for degradation of type-I collagen. Western immunoblot analysis was used to identify interstitial collagenases MMP-8 and MMP-13 in tracheal epithelial lining fluid (TELF). Immunocytochemistry and in situ hybridization were used to determine cellular expression of these 2 collagenases in cells in bronchoalveolar lavage fluid (BALF).

RESULTS

Collagenase activity was approximately 7 times higher in samples obtained from horses with COPD, compared with control horses. During stabling, horses with COPD had significantly higher collagenase activity than after being maintained on summer pasture, when activity was similar to that of control horses. Immunoreactivity of MMP-8 and MMP-13 was significantly increased in TELF of horses with COPD, compared with healthy horses. In TELF, a positive correlation was detected between immunoreactivity of MMP-8 and MMP-13 and the amount of degradation of type-I collagen. Macrophages and epithelial cells were the major cellular sources of MMP-8 and MMP-13.

CONCLUSIONS AND CLINICAL RELEVANCE

Increased collagenase activity in TELF indicates active ongoing disease and, thus, may reflect lung tissue changes in horses with COPD. Measurements of collagenase activity and MMP immunoreactivity may provide additional diagnostic tools to identify the active phase of chronic lung disease.

In vivo collagenase-2 (MMP-8) expression by human bronchial epithelial cells and monocytes/macrophages in bronchiectasis

The purpose of this study was to determine whether other cellular sources than neutrophils can express matrix metalloproteinase (MMP)-8 protein and mRNA in bronchiectatic (BE) lung. The molecular forms of MMP-8 in the BE bronchoalveolar lavage fluid (BALF) and healthy control BALF were analysed by western immunoblotting. MMP-8 expression was demonstrated by immunohistochemistry and in situ hybridization in BE lung tissue and by immunohistochemistry in control lung tissue. In the BE BALF, different MMP-8 species were detected: 70-80 kD MMP-8 apparently of polymorphonuclear leukocyte (PMN) origin and also 40-60 kD MMP-8 from non-PMN cellular sources, such as bronchial epithelial cells, glandular cells or monocytes/macrophages. Both of these MMP-8 species were elevated and converted to a significant extent to activated forms in BE BALF compared with healthy control BALF. The levels of high molecular weight (>80 kD) MMP-8 complexes, evidently representing MMP-8 trapped by endogenous MMP inhibitors and/or MMP-8 dimers, were significantly elevated in BE BALF compared with healthy control BALF. In BE lung tissue, the MMP-8 protein and mRNA expression was found in bronchial ciliated epithelial cells, glandular cells, neutrophils, and monocytes/macrophages infiltrating the bronchial epithelial area. Minimal MMP-8 expression was observed in neutrophils, monocytes/macrophages, and epithelial cells in control lung tissues. In this study, new potential cellular sources have been demonstrated for MMP-8 in the inflamed lung. MMP-8 from multiple cellular sources, including inflamed lung epithelium, was activated to a significant extent in the BE BALF, indicating a major role for MMP-8 in the destruction of lung and bronchial tissues.

Effects of Noninhibitory α-1-Antitrypsin on Primary Human Monocyte Activation in Vitro

A major function of alpha-1-antitrypsin (AAT) is the inhibition of overexpressed serine proteinases during inflammation. However, it is also known that the biological activity of AAT is affected by chemical modifications, including oxidation of the reactive-site methionine, polymerization, and cleavage by unspecific proteases, all of which will result in AAT inactivation and/or degradation. All inactive forms of AAT can be detected in tissues and fluids recovered from inflammatory sites. To test for a possible link between the inflammation-generated, noninhibitory, cleaved form of AAT and cellular processes associated with inflammation, we studied the effects of this form at varying concentrations on human monocytes in culture. We found that cleaved AAT at concentrations ranging between 1 and 10 microM in monocyte cultures over 24 h induces elevation in monocyte chemoattractant protein-1 (MCP-1) and pro-inflammatory cytokines such as TNFalpha and IL-6 and also increases production of interstitial collagenase (MMP-1) and gelatinase B (MMP-9), members of two different classes of matrix metalloproteinase. Moreover, monocytes stimulated with higher doses of cleaved AAT show an increase in cellular oxygen consumption by about 30%, while native AAT under the same experimental conditions inhibits oxygen consumption by about 50%. These results indicate that the cleaved form of AAT may play a role in monocyte recruitment and pro-inflammatory activation during inflammatory processes, and also suggest that changes in structure occurring upon AAT cleavage could alter its functional properties with potential pathological consequences.

Activation of primary human monocytes by the oxidized form of alpha1-antitrypsin

The oxidation of methionine residues in many proteins, including the serine proteinase inhibitor alpha1-antitrypsin (AAT), can result in functional inactivation. In this study we investigated the pro-inflammatory properties of oxidized AAT (oxAAT), specifically its ability to activate human monocytes in culture. Monocytes stimulated with oxAAT at concentrations up to 0.2 mg/ml for 24 h showed significant elevation in monocyte chemoattractant protein-1, cytokine interleukin-6, and tumor necrosis factor-alpha expression and increased NADPH oxidase activity. Monocytes activated with oxAAT showed surprising effects on lipid metabolism. Expression of low density lipoprotein (LDL) receptors increased by up to 76% compared with controls but was not accompanied by any changes in (125)I-labeled LDL binding and, paradoxically, decreased LDL uptake, degradation, and intracellular cholesterol synthesis. oxAAT also down-regulated the scavenger receptor CD36, which takes up and is up-regulated by oxidized LDL and is down-regulated by cholesterol efflux. As a by-product of oxidative events accompanying inflammation, oxAAT has multiple effects on cytokine expression, generation of reactive oxygen species, and on intracellular lipid metabolism. The up-regulation of monocyte-derived reactive oxygen by oxAAT could potentially result in self-amplification of AAT oxidation and, thereby, the other effects deriving from it. This implies that there are as yet unidentified regulatory processes that control this cycle.

The expression of MMP-8 in human odontoblasts and dental pulp cells is down-regulated by TGF-beta1

Recent findings show that matrix metalloproteinase-8 (MMP-8) is expressed, in addition to neutrophils, by human chondrocytes, cultured fibroblasts, and endothelial cells. We investigated the expression of MMP-8 in other human mesenchyme-derived cells, odontoblasts, and pulp tissue. Odontoblasts and pulp tissue were collected from extracted human teeth for MMP-8 mRNA analysis with reverse-transcription/polymerase chain-reaction (RT-PCR) and Southern blot. The expression, localization, and secretion of MMP-8 protein were studied with Western blot, immunohistochemistry, and immunofluorometric assay. The effect of TGF-beta1 (10 ng/mL) on the expression, secretion, and concentration of secreted MMP-8 was studied by odontoblast and pulp tissue culture methods (Tjäderhane et al., 1998a). RT-PCR demonstrated MMP-8 mRNA expression in native and cultured odontoblasts and pulp tissue and cultured pulp fibroblasts, with a 522-bp transcript comparable with that of bone marrow cells. The specificity of PCR was confirmed with Southern blot. Western blot with MMP-8-specific antibody detected 65- and 50-kDa proteins in native samples, representing latent and active forms of mesenchymal-type MMP-8, and in the conditioned odontoblast culture media, 50-kDa protein was observed. TGF-beta down-regulated the MMP-8 mRNA and concentration of secreted protein in both cultures. Immunohistochemical staining detected MMP-8 in odontoblasts. These findings indicate that mesenchyme-derived cells of the dentin-pulp complex express, synthesize, and activate MMP-8, which may, in concert with odontoblast-derived gelatinases, participate in organization of dentin organic matrix prior to mineralization.

Atherogenic properties of human monocytes induced by the carboxyl terminal proteolytic fragment of alpha-1-antitrypsin

Atherosclerotic plaques contain a significant number of macrophage foam cells and are associated with an inflammatory state. Inflammation induces the secretion from monocytes and other cells of cytokines, reactive oxygen species, proteinases and proteinase inhibitors among many other molecular species. AAT is prominent among the serine proteinase inhibitors and is an important regulator of leukocyte elastase and proteinase-3. It has been shown that the stable AAT-proteinase complex can upregulate AAT biosynthesis, and we have shown that the shorter, carboxyl terminal peptide (C-36) resulting from proteinase cleavage of AAT polymerizes, and in its fibrillar form alters cellular metabolism. To test for a possible link between the inflammation-generated C-36 peptide and cellular processes associated with atherogenesis, we have studied the effects of the fibrillar form of this peptide at varying concentrations on human monocytes in culture. We have found that fibrillar C-36 at concentrations of greater than or equal to 5 micromol/l in monocyte cultures for 24 h significantly increases LDL binding and uptake, upregulates LDL receptors, induces cytokine production and glutathione reductase activity, and upregulates AAT synthesis. The expression of CD36 protein, LDL Scavenger receptor, is also upregulated by fibrillar C-36 and native LDL in the presence of C-36-activated monocytes is more oxidized than with unactivated control monocytes. The majority of monocytes cultured for 24 h in the presence of C-36 fibrils were transformed morphologically into macrophages. These data establish a direct molecular link, mediated by C-36 peptide of AAT, between inflammation and the oxidation and accumulation of lipid in monocyte-derived macrophages. This may be important for an understanding of the events conducive to atherogenesis.

Human monocyte activation by cleaved form of alpha-1-antitrypsin involvement of the phagocytic pathway

Production of alpha-1-antitrypsin (AAT) by human monocytes is an important factor in controlling tissue damage by proteases in the microenvironment of inflammation. Increases, of four- to eightfold, in numbers of macrophages and levels of AAT and its cleavage fragments have been found in various inflammatory loci. We have found that the C-terminal peptide (C-36) of AAT, produced by specific proteinase cleavage when added in its fibrillar form at concentrations >/=5 microM to monocytes in culture for 24 h, significantly increases low density lipoprotein (LDL) binding and uptake, up-regulates levels of LDL receptors and also induces proinflammatory cytokine (interleukin-1, interleukin-6 and tumour necrosis factor alpha) production and glutathione reductase activity. Because it is known that various cells selectively internalize surface receptors and their ligands through receptor-mediated endocytosis via clathrin-coated pits, we tested whether antibodies raised against the clathrin heavy chain would block the effects of the fibrillar form of C-36 on human monocytes in culture. Addition of excess anti-(clathrin HC) with 10 microM fibrillar C-36 diminished the stimulatory effects of the latter on LDL binding, uptake and LDL receptor levels. In contrast, however, in the presence of anti-(clathrin HC), the potentially cytotoxic effects of fibrils, such as induction of cytokines, free radicals and cytosolic activity of cathepsin D, were much greater than those observed when cells were treated with fibrils alone. These results suggest that endocytosis is the pathway by which C-36 fibrils upregulate LDL receptors, and may be the natural mechanism for fibril clearance. We infer that human monocytes clear C-36 fibrils by a clathrin-dependent pathway, presumably endocytotic, and that loss of this pathway amplifies the cytotoxic effects of the fibrils by increasing their availability to other specific or nonspecific sites through which they exert their cytotoxic effects.

The proteolytic environment of chronic wounds

A consistent feature of chronic leg and pressure ulcers is chronic inflammation associated with an elevated infiltration of neutrophils. Neutrophils and their proteases have been implicated in mediating the tissue damage associated with a variety of chronic inflammatory diseases. This review discusses our current understanding of the proteolytic enzymes found in chronic wounds and attempts to relate this information to the abundant presence of neutrophils. In addition, the implications that the proteolytic environment may have for current and future treatment strategies of chronic nonhealing wounds are discussed.

Effects of fibrillar C-terminal fragment of cleaved alpha1-antitrypsin on cholesterol homeostasis in HepG2 cells

Amyloid fibrils of diverse origin are known to disturb vital cellular functions and induce cell death. In this study, the effects of amyloid fibrils from the C-terminal fragment (C-36) of cleaved alpha1-antitrypsin (AAT) on low-density lipoprotein (LDL) metabolism were investigated in HepG2 cells. Treatment of the cells with C-36 fibrils (10 micromol/L) enhanced 125I-LDL binding and uptake 10 to 15 times, and highly up-regulated levels of LDL receptor mRNA, as compared with control cells. Competition experiments using excess of unlabeled LDL and blockage experiments with a monoclonal LDL receptor antibody diminished or completely abolished the stimulatory effects of fibrils on LDL binding and LDL receptor mRNA levels, suggesting that fibrils act via the LDL receptor pathway. However, C-36 fibrils had no significant effect on [2-14C]acetate incorporation into cholesterol biosynthesis and cholesterol ester formation, but inhibited 125I-LDL degradation by 20% and reduced bile acid biosynthesis up to 48% in a dose-dependent manner. Preincubation of the cells with fibrils before the addition of LDL totally abolished the LDL inhibitory effect on unesterified cholesterol synthesis, further confirming the LDL receptors to be the target for C-36 fibrils. Moreover, the expression of sterol regulatory element binding protein-1 (SREBP-1) was found to increase twofold and more after 24 hours of incubation of the cells with several concentrations of C-36 fibrils. Our study suggests that the cytotoxicity of C-36 fibrils on HepG2 cells is associated with perturbed intracellular cholesterol homeostasis, induced through fibril-stimulated expression of the LDL receptors via the sterol-responsive element.

Tetracyclines inhibit connective tissue breakdown by multiple non-antimicrobial mechanisms

A seminal experiment involving a germ-free rat model of connective tissue breakdown (followed soon thereafter by a series of in vitro studies) identified an unexpected non-antimicrobial property of tetracyclines (TCs). This ability of TCs to inhibit matrix metalloproteinases (MMPs) such as collagenase was found to reflect multiple direct and indirect mechanisms of action, and to be therapeutically useful in a variety of dental (e.g., adult periodontitis) and medical (e.g., arthritis, osteoporosis, cancer) diseases. The site on the TC molecule responsible for its MMP-inhibitory activity was identified which led to the development of a series of chemically modified non-antimicrobial analogs, called CMTs, which also have therapeutic potential but do not appear to induce antibiotic side-effects. Longitudinal double-blind studies on humans with adult periodontitis have demonstrated that a sub-antimicrobial dose of doxycycline (previously reported to suppress collagenase activity in the periodontal pocket) is safe and effective and has recently been approved by the FDA as an adjunct to scaling and root planing.

Matrix metalloproteinase-8 is expressed in rheumatoid synovial fibroblasts and endothelial cells. Regulation by tumor necrosis factor-alpha and doxycycline

Neutrophil collagenase (matrix metalloproteinase-8 or MMP-8) is regarded as being synthesized exclusively by polymorphonuclear neutrophils (PMN). However, in vivo MMP-8 expression was observed in mononuclear fibroblast-like cells in the rheumatoid synovial membrane. In addition, we detected MMP-8 mRNA expression in cultured rheumatoid synovial fibroblasts and human endothelial cells. Up-regulation of MMP-8 was observed after treatment of the cells with either tumor necrosis factor-alpha (10 ng/ml) or phorbol 12-myristate 13-acetate (10 nM). Western analysis showed a similar regulation at the protein level. The size of secreted MMP-8 was 50 kDa, which is about 30 kDa smaller than MMP-8 from PMN. Conditioned media from rheumatoid synovial fibroblasts contained both type I and II collagen degrading activity. However, degradation of type II collagen, but not that of type I collagen, was completely inhibited by 50 microM doxycycline, suggesting specific MMP-8 activity. In addition, doxycycline down-regulated MMP-8 induction, at both the mRNA and protein levels. Thus MMP-8 exerts markedly wider expression in human cells than had been thought previously, implying that PMN are not the only source of cartilage degrading activity at arthritic sites. The inhibition of both MMP-8 activity and synthesis by doxycycline provides an incentive for further studies on the clinical effects of doxycycline in the treatment of rheumatoid arthritis.

Human neutrophil collagenase MMP-8 in peri-implant sulcus fluid and its inhibition by clodronate

The exact molecular mechanisms of the loosening of a dental implant are not well-known. The characteristics of implant sulci are similar to those of periodontal sulci regarding gingival crevicular fluid (GCF) and peri-implant sulcular fluid (PISF). Proteolytic enzymes, matrix metalloproteinases (MMPs), participate in peri-implant tissue remodeling. Clodronate is a well-tolerated bisphosphonate-group drug currently used in bone-resorption-related diseases in humans. The mechanisms of bisphosphonate action are not clarified. Collagenase activity in diseased PISF was significantly higher than in the clinically healthy group. Immunoblotting disclosed that diseased PISF contained increased immunoreactives MMP-8 compared with the healthy PISF. The residual latent collagenase activity in the diseased PISF was activated by gold thioglucose and inhibited completely by 100 microM of doxycycline closely resembling pure neutrophil collagenase (MMP-8). The presence of MMP-8 in diseased but not in clinically healthy PISF may prove to be a useful biochemical indicator to monitor peri-implant health and disease. Pure human neutrophil collagenase (MMP-8) and the MMP-8 present in PISF and in the GCF of both loosening implants and periodontitis-affected teeth were efficiently inhibited in vitro by clodronate (50% inhibition [IC50] was achieved by 150 microM of clodronate), an osteoactive, antiresorptive bisphosphonate. Furthermore, the new finding suggests an extended and hitherto-undescribed potential for clodronate in preventing the loosening of both implants and teeth, based on a dual beneficial effect: prevention of both bone resorption/osteolysis and of soft tissue/dental ligament destruction. Potential new therapeutic indications based on the collagenase-inhibiting effect of clodronate provide potential new therapeutic indications for a variety of diseased involving connective tissue breakdown, such as periodontal disease, arthritides, and tumor invasion.

Inhibition of human serine proteases by SPAAT, the C-terminal 44-residue peptide from alpha1-antitrypsin

SPAAT has previously been shown to be a competitive inhibitor of the model serine protease, chymotrypsin. We now present evidence that SPAAT is likewise a competitive inhibitor of human neutrophil elastase and cathepsin G with Ki's of 15-20 and 40 microM, respectively. The mechanism of this inhibition was investigated by comparing the relative effectiveness of the 23-residue N-terminal fragment of SPAAT (N-SPAAT) to inhibit chymotrypsin and human neutrophil elastase. N-SPAAT, which does not contain the primary chymotrypsin cleavage site, was approximately 10-fold less effective as an inhibitor of chymotrypsin than SPAAT (Ki of 65 microM versus 7.5 microM). In contrast, this fragment, which contains the primary human neutrophil elastase cleavage site, was found to competitively inhibit human neutrophil elastase with a Ki of 24 microM which was comparable to that of SPAAT (Ki = 15-20 microM). Thus it appears that SPAAT is a reversible inhibitor of these enzymes rather than an irreversible, stoichiometric one like its parent protein, AAT. Such fragmentation of AAT, however, might provide a mechanism whereby a cascade of decreasingly potent, but increasingly specific SPAAT-related inhibitory peptides could be generated. These results further substantiate the view that SPAAT may play a role in vivo in the protection of extracellular proteins from inappropriate attack by proteases which are elevated during various pathophysiological conditions.

alpha 1-Proteinase inhibitor in gingival crevicular fluid of humans with adult periodontitis: serpinolytic inhibition by doxycycline

The serum protein, alpha 1-proteinase inhibitor (alpha 1-PI), defends the host against serine proteinases, e.g. PMN elastase. Using a rabbit anti-serum against human alpha 1-PI, this protein in GCF was quantified from a standard curve constructed from dot-blot analysis and characterized by Western blot. GCF was collected on filter paper strips from healthy (H), gingivitis (G) and adult periodontitis (AP) patients, then extracted with Tris/NaCl/CaCl2 buffer, pH 7.6. alpha 1-PI concentration increased with G and was highest in AP subjects. H sites only showed intact alpha 1-PI (52 kDa); no degradation fragments (48 kDa) were detected. In G and AP subjects, alpha 1-PI degradation fragments were seen in 17% and 71% of GCF samples, respectively. Both collagenase and alpha 1-PI-degrading activities in GCF increased with severity of inflammation (GCF flow). Moreover, the alpha 1-PI degrading (or serpinolytic) activity was characterized as a matrix metalloproteinase, probably collagenase, based on its in vitro response to a panel of different proteinase inhibitors including doxycycline. We propose: (1) that collagenase promotes periodontal breakdown not only by degrading collagen, but also by depleting alpha 1-PI regulation of elastase and other serine-proteinases, thereby favoring a broader attack on extracellular matrix (ECM) constituents, and (2) based on a recent longitudinal double-blind study using the techniques described above for alpha 1-PI analysis, that low-dose doxycycline administration to humans with adult periodontitis can inhibit this broad cascade of ECM degradation.

Acute phase proteins and transformed cells

Acute phase proteins (APP) are plasma proteins whose concentration and glycosylation alters in response to tissue injury, inflammation, or tumor growth. Significant interspecies and sex differences in APP response exist. APP are produced mainly by hepatocytes, and their synthesis and glycosylation are controlled by a network consisting of cytokines, their soluble receptors, and glucocorticoids. The major cytokines involved in these processes belong to a group of interleukin-6-type cytokines that act through the hematopoietin receptor complex on hepatocytes and JAK-STAT signal transduction pathway. Transformed cells (hepatoma) display significant differences in synthesis of APP, cytokine responsiveness, expression of cytokine-receptor subunits and signal-transduction machinery. The most striking variability relates to the glycosylation alterations induced by cytokines. However, transformed cells (hepatoma) form a basic model for studying and understanding mechanisms controlling the synthesis and glycosylation of APP. Furthermore, APP may be secreted by transformed (tumor) cells of various origins and may display a growth factor-like function in certain cancer types.

Stromal expression of MMP-9 and urokinase receptor is inversely associated with liver metastasis and with infiltrating growth in human colorectal cancer: a novel approach from immune/inflammatory aspect

MMP-9 (gelatinase B) and urokinase-type plasminogen activator receptor (u-PAR), which are involved in cancer cell invasion and metastasis, are reported to be predominantly expressed by immune/inflammatory cells in human colorectal cancers. To investigate their significance in cancer progression, we morphometrically analyzed the tissue expression of MMP-9 and u-PAR among different stages of colorectal cancer. The numbers of MMP-9- and u-PAR-positive cells along the invasive margin were significantly smaller in cases with liver metastasis than in cases without liver metastasis, and were also smaller in cases with an infiltrating margin than in cases with an expanding margin. Both variables were larger in colon cancer cases with conspicuous lymphocytic infiltration. These results indicated that the degree of tissue expression of MMP-9 and u-PAR by host cells is inversely associated with liver metastasis and an infiltrating growth pattern in human colorectal cancers. Essentially the same results were obtained for the number of macrophages distributed along the invasive margin. We also found that the expression pattern of MMP-9 was similar to that of MMP-8 (polymorphonuclear leukocyte collagenase). These data are consistent with clinicopathologic studies of host cells. Therefore, our data suggest a dual role of MMP-9 and u-PAR expression in colon cancer tissue; i.e., not only are these proteinases cancer-promoting factors, but also they are related to the host defensive mechanism when they are expressed by host cells.

Matrix metalloproteinases-1, -3 and -8 and myeloperoxidase in saliva of patients with human immunodeficiency virus infection

OBJECTIVE

Human immunodeficiency virus (HIV)-seropositive patients have frequently severe gingival inflammation and/or attachment loss. In addition many infectious diseases affect their periodontium with varying clinical manifestations. Matrix metalloproteinases seem to play a key role in physiological periodontal remodelling and pathological tissue destruction. The aim of the present study was to characterize the presence, molecular forms, cellular sources, activities, and relative amounts of fibroblast-type (matrix metalloproteinase [MMP]-1) and neutrophil (MMP-8) collagenases, as well as their potential activator stromelysin-I (MMP-3) and myeloperoxidase in saliva of HIV-seropositive patients at different phases of HIV-infection. HIV-seronegative, healthy, age-matched patients served as controls.

PATIENTS AND METHODS

Saliva samples were characterized by Western blotting using antibodies specific for MMP-1, MMP-3 and MMP-8. Interstitial collagenase activities were measured using quantitative sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis/laser densitometry assay. Myeloperoxidase was analysed using quantitative dot blotting.

RESULTS

Clinical and microbiological evaluation of HIV-seropositive patients' periodontium showed the presence of putative periodontopathogens ie Actinobacillus actinomycetemcomitans (Aa), Porphyromonas gingivalis (Pg), Prevotella intermedia (Pi), Peptostreptococcus micros (Psm) and Campylobacter rectus (Cr) in their periodontal pockets. The amount of Candida increased with the severity of HIV-infection. Clinical and microbiological findings of HIV-seropositive patients suggested that they have a tendency to develop periodontal disease. Interstitial collagenase activities were found to be increased in saliva of different phases of HIV-infected patients compared to the controls. Independent of the phase of HIV-infection saliva samples contained pro- and active forms of MMP-1, -3 and -8 using Western blotting. Saliva samples from healthy controls were found to contain hardly any immunoreactivities for MMP-1 or MMP-8, but considerable amounts of MMP-3 were detected. Quantitative dot blotting demonstrated increased amounts of myeloperoxidase in HIV-patients' saliva relative to controls.

CONCLUSION

The present results showed increased amounts of MMP-1, -3, -8 and myeloperoxidase in HIV-patients' saliva. MMP-1 and -8 may have been activated by MMP-3 and/or oxidants generated by myeloperoxidase. The increased amounts of MMPs and myeloperoxidase may reflect and directly participate in HIV-infection associated periodontitis.

Membrane components of Treponema denticola trigger proteinase release from human polymorphonuclear leukocytes

Tissue destruction during periodontitis is believed to be primarily brought about by leukocyte proteinases. We postulate that oral spirochetes cause discharge of polymorphonuclear leukocyte (PMN) lysosomal enzymes. Effects of Treponema denticola 53-kDa outer membrane protein, lipopolysaccharide (LPS), and peptidoglycan on degranulation of matrix metalloproteinases (MMP)-8 (collagenase) and -9 (gelatinase), cathepsin G, and elastase by human peripheral blood PMNs were studied by specific enzyme assays and Western blot analysis. T. denticola 53-kDa kDa outer membrane protein was found to be a particularly efficient inducer of MMP-8 release. The induction was comparable with that of phorbol myristate acetate, a known inducer of PMN specific granule discharge. All of the treponemal substances, most notably the 53-kDa protein and LPS, induced release of MMP-9, a component of C-type granules. Both collagenase and gelatinase released from PMNs were mostly in active forms. Release of cathepsin G and elastase was also observed with the 53-kDa protein treatment. The other T. denticola substances did not induce release of these serine proteinases. Lactate dehydrogenase was not released from PMNs by the treatments, indicating that the degranulation was specific and not caused by toxic effects of the substances. This was confirmed by transmission electron microscopy of PMNs treated with the 53-kDa protein that showed rapid vacuole formation and cell shape changes but no disintegration of the cells. Thus, T. denticola may participate in the PMN-dependent extracellular matrix degradation during the course of periodontal inflammation by triggering the secretion and activation of matrix metalloproteinases.

Matrix metalloproteinases, gelatinase and collagenase, in chronic leg ulcers

Although extracellular proteolysis is a prerequisite for normal wound healing, uncontrolled proteolytic tissue destruction appears to be a pathogenic factor in non-healing wounds. The aim of our study was to compare the activities of the serine proteinases of polymorphonuclear origin, elastase and cathepsin G, and the metalloproteinases, gelatinase and collagenase, in chronic leg ulcer exudate (10 patients) and acute wound fluid (6 patients). Serine proteinase activities were low in leg ulcer exudates but very high in some but not all acute wound fluids. Total collagenase activity, measured as activity against type I collagen monitored by SDS-PAGE and densitometry, was higher in chronic leg ulcer exudate than in acute wound fluid and its degree of autoactivation was relatively high. Doxycycline inhibition studies suggested that the collagenase activity in chronic leg ulcer exudate was MMP-1 ("fibroblast-type") and not MMP-8 ("neutrophil-type"). Zymographic analysis of the gelatinolytic enzymes in acute wound fluid showed a progressive increase from the day of operation to postoperative day 5, but the degree of activity was lower than in chronic leg ulcer exudate and the low molecular mass activation products were faint. The leg ulcer gelatinase profiles were characterized by high expression of 92/82- and 72/62-kDa duplex bands and by the presence of low molecular mass activation products. Leg ulcer collagenase seems to be derived from mononuclear rather than polymorphonuclear cells, which are known to be involved in acute wound healing. In conclusion, the present study shows that gelatinase and collagenase, but not elastase and cathepsin G are found in chronic leg ulcer exudate.

The "cyclic" regimen of low-dose doxycycline for adult periodontitis: a preliminary study

Specially-formulated low-dose doxycycline (LDD) regimens have been found to reduce collagenase activity in the gingival tissues and crevicular fluid (GCF) of adult periodontitis subjects in short-term studies. In the current, double-blind, placebo-controlled study, adult periodontitis patients were administered for 6 months a "cyclical" regimen of either LDD or placebo capsules; and various clinical parameters of periodontal disease severity, and both collagenase activity and degradation of the serum protein, alpha 1-PI, in the GCF were measured at different time periods. No significant differences between the LDD- and placebo-treated groups were observed for plaque index and gingival index. However, attachment levels, probing depth, and GCF collagenase activity and alpha 1-PI degradation were all beneficially and significantly (P < 0.05) affected by the drug regimen. We propose: 1) that LDD inhibits tissue destruction in the absence of either antimicrobial or significant anti-inflammatory efficacy; and 2) that long-term LDD could be a useful adjunct to instrumentation therapy in the management of the adult periodontitis patient.

Cathepsin G in gingival tissue and crevicular fluid in adult periodontitis

The presence, localization and activities of cathepsin G in gingival tissue specimens and crevicular fluid (GCF) from 9 adult periodontitis patients and 6 controls with clinically healthy periodontium were studied by use of avidinbiotin-peroxidase complex method, Western and dot blotting, and spectrophotometric activity assay. In contrast to healthy gingival tissue specimens, gingival tissue specimens collected from adult periodontitis patients contained inflammatory cells in lamina propria, beneath the oral sulcular epithelium, 10-50% of which were cathepsin G positive polymorphonuclear neutrophilic leukocytes (PMNs) and monocyte/macrophage-like cells. Cathepsin G activities were increased in adult periodontitis GCF when compared to periodontally healthy controls' GCF (p < 0.05). In adult periodontitis GCF, Western blotting disclosed free cathepsin G but also clear complexes of cathepsin G with its predominant endogenous inhibitor alpha 1-antichymotrypsin (alpha 1-ACT). The present results demonstrate that part of the cathepsin G, despite the presence of increased concentrations of alpha 1-ACT, was in an uncomplexed, free and functionally active form. Our results suggest that GCF cathepsin G reflects the disease process in adjacent inflamed gingiva and also increased host response to microbiota and/or dental plaque in the periodontitis lesions. Cathepsin G may contribute to periodontal tissue destruction directly and indirectly, via proteolytic activation of latent neutrophil procollagenase (promatrix metalloproteinase-8 [proMMP-8]).

Determination of metalloproteinases, plasminogen-activators and their inhibitors in the synovial fluids of patients with rheumatoid arthritis during chemical synoviorthesis

The concentrations of matrix metalloproteinase-1 (MMP-1), matrix metalloproteinase-8 (MMP-8), matrix metalloproteinase-9 (MMP-9), lactoferrin and urokinase plasminogen activator (uPA), tissue-type plasminogen activator (tPA) and the inhibitors, tissue inhibitor of metalloproteinase-1 (TIMP-1), plasminogen activator inhibitor-1 (PAI-1), plasminogen activator inhibitor (PAI-2), and alpha2-macroglobulin in the synovial fluids of patients with rheumatoid arthritis was determined before and during chemical synoviorthesis with a sodium salt of the fatty acids from cod-liver oil (Varicocid). Synovial fluids were obtained before treatment from 37 patients with rheumatoid arthritis and, in most cases, at 8 and 24 h after injection of the agent. Well-established ELISAs were used to determine the amounts of all proteins. All patients with rheumatoid arthritis revealed very high levels of metalloproteinases (about 1-15 mu g/ml) in their synovial fluids. During the inflammation inducing treatment the granulocyte enzymes increased. In contrast to this, the level of MMP-1 decreased. All granulocyte-derived enzymes were strongly correlated with each other, whereas their dependence on the granulocyte count was only weak. uPA and PAI-2 showed good correlations with the granulocytes-derived enzymes, but were also only weakly correlating with the cell counts. t-PA was not detected by the ELISA used. The proteases, MMP-8, MMP-9 and uPA were increased 8 h after the treatment, whereas the specific inhibitors TIMP-1, PAI-1 and PAI-2 showed significant changes only 24 h after the injection. Matrix metalloproteinases are important factors in the pathogenesis of rheumatoid arthritis. The inflammatory activity in the joint could be better correlated to the granulocyte enzymes than to the granulocyte counts. The levels of uPA and PAI-2 are also parallel to the granulocyte enzyme levels and might underly the same regulatory mechanism.

Alpha 1-antitrypsin is degraded and non-functional in chronic wounds but intact and functional in acute wounds: the inhibitor protects fibronectin from degradation by chronic wound fluid enzymes

Fluid obtained from chronic and acute wounds were examined for the presence of fibronectin, alpha 1-antitrypsin, and proteinases capable of degrading both proteins. Immunoblot analysis of fluids from ten chronic wounds revealed that fibronectin and alpha 1-antitrypsin were degraded in nine of ten samples. In contrast, both fibronectin and alpha 1-antitrypsin were intact in acute wound fluids. The degradation of the inhibitor and fibronectin occurred in the same wound fluids, and these two events correlated perfectly. Chronic or acute wound fluid proteins were coupled to benzamidine Sepharose 6B beads and incubated with fibronectin or alpha 1-antitrypsin. Chronic wound fluid proteins degraded fibronectin in the presence of ethylenediaminetetraacetate, leupeptin, cystatin, and pepstatin but not in the presence of phenylmethylsulfonyl fluoride. Acute wound fluids and normal human serum did not contain enzymes capable of degrading fibronectin. These data suggest that serine proteinases are responsible for fibronectin degradation in chronic wound fluids. Chronic wound fluids that contained degraded alpha 1-antitrypsin also contain proteinases capable of degrading alpha 1-antitrypsin from human serum. Acute wound fluids and normal human serum did not contain enzymes capable of degrading alpha 1-antitrypsin. The inhibitor from acute wound fluids bound to one of its targets, trypsin. In contrast, the fragment(s) of alpha 1-antitrypsin from chronic wound fluids did not bind trypsin. Chronic wounds associated with degraded fibronectin and the inhibitor contained ten- to forty-fold more elastase activity than acute wounds. The degradation of fibronectin by chronic wound fluid enzymes was inhibited by alpha 1-antitrypsin in a dose-dependent manner. Collectively, these results demonstrate that there are enzymes in chronic wounds that perturb the function of alpha 1-antitrypsin and allow fibronectin degradation by uninhibited serine proteinases.

Characterization of interstitial collagenases in jaw cyst wall

Neutral salt extracts of 14 specimens of jaw cysts were prepared. Histopathological analysis showed that the specimens consisted of 6 radicular cysts, 6 dentigerous cysts, 1 residual cyst, and 1 odontogenic keratocyst. One periapical granuloma, 1 dental follicle and a sample of clinically healthy oral mucosa were similarly processed and used as controls. Measurement of collagenase activity by monitoring the formation of specific degradation products of type I and II collagen in solution by SDS-PAGE demonstrated that all the cyst extracts contained collagenase, some of which was endogenously activated. Cyst wall collagenase preferably degraded type I over type II collagen, which suggests that the degradation was due to MMP-1 (matrix metalloproteinase-1) rather than the MMP-8 type. This was further supported by the doxycycline-inhibition profile of cyst collagenase, which was similar to that of MMP-1. Part of the cyst wall collagenase was in latent proenzyme form and probably derived, at least in part, from the newly synthesized intracellular collagenase pool. Latent cyst collagenase was efficiently activated with phenylmercuric chloride and to a lesser extent by gold (I) thioglucose and NaOCl. Western-blotting, using specific antibodies against collagenase from human polymorphonuclear neutrophilic leukocytes (MMP-8) and from fibroblasts (MMP-1), revealed a typical 55/45 kDa doublet; also MMP-8 in the latent 80 kDa form and fragmented to 65 kDa active species were found. These results suggest the presence of MMP-1 and, to a lesser extent, MMP-8 type collagenase in the cyst wall.(ABSTRACT TRUNCATED AT 250 WORDS)

Human neutrophil collagenase (MMP-8), identified in bronchiectasis BAL fluid, correlates with severity of disease

Collagenases in bronchoalveolar lavage fluid (BALF) of patients with bronchiectasis and healthy subjects were characterized using specific functional and immunologic assays. The BAL fluid contained interstitial collagenase and collagenolytic proteinases of bacterial origin. Collagenase activities, obtained after organomercurial activation, correlated with the severity of bronchiectasis. In severe cases, collagenase activities were 3.5 x 10(-7) IU/L/48 h or 4.8 x 10(-6) IU/g/48 h (p < 0.01), in moderate ones 1.74 x 10(-7) IU/L/48 h or 3.35 x 10(-6) IU/g/48 h (p < 0.05), and in mild cases 0.32 x 10(-7) IU/L/48 h or 0.7 x 10(-6) IU/g/48 h (p < 0.05). The corresponding activities in healthy control subjects were 0.08 x 10(-7) IU/L/48 h or 0.13 x 10(-6) IU/g/48 h. The cellular origin of interstitial collagenase was assessed with doxycycline inhibition test utilizing the differential sensitivity of fibroblast-type collagenase/MMP-1 (IC50 = 280 microM) and neutrophil-type collagenase/MMP-8 (IC50 = 26 microM) to the anticollagenolytic, nonantimicrobial doxycycline action. Interstitial collagenase, contained in BALF, was totally inhibited by 100 microM of doxycycline. It can therefore be concluded that most of mammalian collagenase presented in inflamed fluid of bronchiectasis originated from neutrophils. The molecular forms of neutrophil-type collagenase/MMP-8 were confirmed and analyzed by Western-blot, which showed evidence of the proteolytic conversion of the latent 85-kD MMP-8 proenzyme species into active 65-kD molecular weight species. These findings strongly suggest involvement of proteolytic activation pathway of proMMP-8, especially in severe and moderate forms of bronchiectasis. Furthermore, collagenolytic proteases of bacterial origins may also participate in tissue destruction of the lung.

Limited proteolysis of alpha 1-proteinase inhibitor (alpha 1-PI) in acute leukemia: studies on the resulting fragments and implication for the structure of the inactivated inhibitor

In patients with acute myeloid leukemia, a 41 kDa glycoprotein appears in the urine during remission induction chemotherapy. We have recently reported on the isolation and preliminary characterization of this protein and the generation of specific monoclonal antibodies which showed that it is a proteolytically modified form of alpha 1-proteinase inhibitor (Dengler et al., 1992, Biol. Chem. Hoppe-Seyler 373, 581-588). In the paper presented here, results from further characterization experiments as well as from studies on the effects of proteolysis on the conformation and the resulting functional properties of the truncated inhibitor are reported. N-terminal amino acid sequence analysis showed that proteolysis has occurred in the N-terminal part as well as in the reactive site loop of alpha 1-PI. The resulting core protein of 41 kDa is composed of approximately 324 amino acid residues with the C-terminus located close to Lys343 of alpha 1-PI.A 4 kDa peptide remaining bound to this fragment throughout the entire purification procedure could be separated by SDS treatment. N- and C-terminal sequence analysis of this peptide after isolation by gel filtration showed that it is comprised of residues Ile359 up to Lys394, thus representing the peptide located C-terminal to the reactive site loop of alpha 1-PI. Transverse urea gradient gel electrophoresis indicates that the proteolyzed inhibitor is in the thermodynamically stable, relaxed (R)-conformation known for proteinase-complexed and cleaved serpins. The truncated inhibitor exhibits no chemotactic activity towards neutrophils when tested in a standard assay.

Effects of interleukin-6 (IL-6) and transforming growth factor-beta (TGF-beta) on neutrophil elastase release

The proinflammatory cytokine interleukin-6 (IL-6) and its potential opponent, transforming growth factor-beta (TGF-beta 1), have been discussed as being involved in the regulation of inflammatory processes following trauma and infections. The aim of this study was to investigate the effect of these cytokines on the regulation of neutrophil degranulation. The posttraumatic time courses of the plasma concentrations of IL-6, and the elastase-alpha 1-proteinase-inhibitor complex as marker of degranulation in patients undergoing severe trauma were found to be highly correlated, whereas TGF-beta 1 levels were determined to be not significantly altered. The close temporal correlation of IL-6 and elastase levels could be confirmed by investigation of exudates derived from the surgical area. To prove these in vivo findings, the effect of IL-6 and TGF-beta 1 on the degranulation of isolated neutrophils of healthy donors was investigated in vitro. Pathological high IL-6 concentrations were found to be capable of inducing a significant release of lysosomal elastase in a concentration-dependent manner, whereas the degranulation was unaffected by TGF-beta 1. In conclusion, these data suggest an involvement of IL-6 in the regulation of neutrophil degranulation under pathological conditions. However, TGF-beta 1 seems to have no direct regulatory effects besides its described chemotactic function on neutrophils.

Doxycycline inhibits neutrophil (PMN)-type matrix metalloproteinases in human adult periodontitis gingiva

We previously reported that low-dose doxycycline (DOXY) therapy reduces host-derived collagenase activity in gingival tissue of adult periodontitis (AP) patients. However, it was not clear whether this in vivo effect was direct or indirect. In the present study, inflamed human gingival tissue, obtained from AP patients during periodontal surgery, was extracted and the extracts partially purified by (NH4)2SO4 precipitation. The extracts were then analyzed for collagenase activity using SDS-PAGE/fluorography/laser densitometry, and for gelatinase activity using type I gelatin zymography as well as a new quantitative assay using biotinylated type I gelatin as substrate. DOXY was added to the incubation mixture at a final concentration of 0-1000 microM. The concentration of DOXY required to inhibit 50% of the gingival tissue collagenase (IC50) was found to be 16-18 microM in the presence or absence of 1.2 mM APMA (an optimal organomercurial activator of latent procollagenases); this IC50 for DOXY was similar to that exhibited for collagenase or matrix metalloproteinase (MMP)-8 from polymorphonuclear leukocytes (PMNs) and from gingival crevicular fluid (GCF) of AP patients. Of interest, Porphyromonas gingivalis collagenase was also inhibited by similar DOXY levels (IC50 = 15 microM), however the collagenase activity observed in the gingival tissue extracts was found to be of mammalian not bacterial origin based on the production of the specific alpha A (3/4) and alpha B (1/4) collagen degradation fragments. In contrast, the inhibition of collagenase purified from culture media of human gingival fibroblasts (MMP-1) required much greater DOXY levels (IC50 = 280 microM). The predominant molecular forms of gelatinolytic activity presented in the AP patients gingival tissue extracts were found to closely correspond to the 92 kD PMN-type gelatinase (MMP-9) although small quantities of 72 kD fibroblast-type gelatinase (MMP-2), and some other low molecular weight gelatinases, were also detected. The IC50 of DOXY versus gingival tissue gelatinolytic activity was estimated at 30-50 microM measure using either type I gelatin zymography or the biotinylated type I gelatin assay. We conclude that MMPS in inflamed gingival tissue of AP patients, like those in GCF, originate primarily from infiltrating PMNs rather than resident gingival cells (fibroblasts and epithelial cells) or monocyte/macrophages, and that their pathologically-elevated tissue-degrading activities can be directly inhibited by pharmacologic levels of doxycycline.