Collagenolytic metalloenzymes of the human neutrophil. Characteristics, regulation and potential function in vivo

Subcellular localization and release of human neutrophil gelatinase, confirming the existence of separate gelatinase-containing granules

An e.l.i.s.a. was developed using specific polyclonal rabbit antibodies against human neutrophil gelatinase. This assay, in contrast to the functional assay, is independent of activation of gelatinase, and is specific for the detection of gelatinase in both its reduced and unreduced forms. Using this assay, we were able to demonstrate a difference between the subcellular localization of gelatinase on the one hand, and the subcellular localization of vitamin B-12-binding protein, lactoferrin and cytochrome b558 on the other hand. The latter three co-localized in fractions of slightly higher density than gelatinase on a two-layer Percoll density gradient. Furthermore, the release of gelatinase exceeded the release of vitamin B-12-binding protein as well as lactoferrin by a factor of 3-6 following stimulation with formylmethionyl-leucyl-phenylalanine, leukotriene B4 and other soluble stimuli. Thus, although gelatinase has previously been found to co-localize with lactoferrin on immuno-electron microscopy, we confirm the existence of gelatinase-rich and lactoferrin- and vitamin B-12-binding-protein-poor granules, that are lighter and mobilized more easily than specific granules. These gelatinase-containing granules are not the store of cytochrome b558.

Interaction of methyl-xanthines with myeloperoxidase. An anti-inflammatory mechanism

1. Inhibition of myeloperoxidase (MPO)-catalyzed reactions by methyl-substituted xanthines has been investigated. 2. Except for theobromine and caffeine, all xanthines tested were potent inhibitors of the MPO-H2O2-Cl- system. 3. In contrast to methyl substitution in the 1 or 8 position of xanthine, substitution in the 3 or 7 position had a marked effect on the inhibition of MPO catalysis. 4. Two different inhibitory mechanisms were induced; scavenging of hypochlorous acid (HOCl) generated by the MPO system and accumulation of Compound II (ferryl MPO) which is inactive as a catalyst of Cl- oxidation.

Current concepts of the biology of tooth eruption

Tooth eruption is defined as the movement of a tooth from its site of development within the jaws to its position of function within the oral cavity. We present a critical review of evidence for the mechanisms and regulation of the intraosseous and supraosseous phases of eruption, with an emphasis upon the canine premolar model studied by the authors. Analyses at different stages of premolar eruption indicate that selective fragmentation of dental follicle protein DF-95 correlates with the presence of elevated levels of follicular collagenase and stromelysin, and with the onset of premolar movement. A dramatic decrease in these metalloproteinases followed initiation of movement. A biochemical and cell biological model for regulation of tooth eruption is proposed based upon these new and existing data.

Gingival crevicular fluid of patients with gingivitis or periodontal disease: evaluation of elastase-alpha 1 proteinase inhibitor complex

Elastase-alpha 1 proteinase inhibitor (E alpha 1PI) concentrations were assessed in gingival crevicular fluids and evaluated in relation to the clinical signs of periodontal disease. 7 gingivitis patients (group G), 38 patients with adult periodontitis and clinically stable lesions (group AP), 21 patients with rapidly progressive periodontitis and clinically stable lesions (group RPP) and 11 patients with either adult periodontitis or rapidly progressive periodontitis and clinically progressive lesions (group Pr) were studied. 6 healthy subjects served as the control group (group H). Significantly differences were observed in the E alpha 1PI concentration between the healthy, gingivitis, clinically stable periodontitis and clinically progressive periodontitis group. In the control group, no E alpha 1PI was detected. Groups G, AP and RPP showed mean E alpha 1PI concentrations of 10.95 +/- 4.96 micrograms/ml, 35.55 +/- 18.64 micrograms/ml and 38.56 +/- 20.89 micrograms/ml, respectively. In these groups, high enzyme levels were correlated with clinical signs of inflammation. The highest E alpha 1PI levels were observed in the clinically progressive lesions. However, they were not necessarily associated with bleeding on probing or clinical evidence of inflammation. These data suggest that a significant increase in crevicular E alpha 1PI levels may be an early manifestation of a progressive or potentially progressive periodontal lesion.

Substrate specificity and activation mechanisms of collagenase from human rheumatoid synovium

Substrate specificity studies of collagenase extracted from human rheumatoid synovium suggest that synovial pannus tissue overlying articular cartilage may not be particularly active in degradation of cartilage type II collagen, which, considering the poor inherent healing capacity of the articular hyaline cartilage, may exert a protective function against inadvertant tissue damage. Rheumatoid synovial tissue was also used to establish synovial fibroblast cell lines. Treatment of these cells in monolayer cultures with IL-1 leads to collagenase gene activation, increased collagenase production and an almost complete autoactivation of secreted collagenase. Interleukin-1 also activated stromelysin gene suggesting this as a possible mechanism effecting autoactivation. Latent human fibroblast and macrophage collagenase purified from culture medium were efficiently activated by phenylmercuric chloride but also by gold thioglucose, gold sodium thiomalate and HCIO. These new observations support the Cys73 switch activation mechanism. In contrast to neutrophil collagenase, the activation by gold(I) compounds and HCIO was associated with a change in the apparent molecular weight of the fibroblast procollagenase. In addition, gold(I) compounds rendered collagenase more susceptible to thermal denaturation. Thus the fibroblast-type interstitial collagenase, probably derived from fibroblast- and macrophage-like synoviocytes, seems to provide the predominant collagenolytic potential in human rheumatoid synovial tissue. Furthermore, the conditions in synovitis tissue may be such as to favor at least initial activation of collagenase synthesized and secreted in situ.

Mechanisms by which clofazimine and dapsone inhibit the myeloperoxidase system. A possible correlation with their anti-inflammatory properties

The mechanisms by which two anti-leprotic drugs (clofazimine and dapsone), both with anti-inflammatory properties, inhibit myeloperoxidase (MPO)-catalysed reactions, were investigated. The disappearance of NADH fluorescence was used as an assay for its oxidation. Chloride stimulated the oxidation of NADH in the MPO-H2O2 system in a concentration-dependent manner (50-fold at 150 mM NaCl). Under these conditions Cl- is oxidized and the oxidant formed, presumably hypochlorous acid (HOCl), oxidizes NADH. Observations demonstrating the effect of the drugs on the MPO system, are: (1) Inhibition of Cl(-)-stimulated oxidation of NADH. (2) Inhibition of polypeptide modification in a model protein, thyroglobulin (TG). (3) Protection of MPO against loss of catalytic activity caused by chlorinating oxidants generated by the system. (4) Inhibition of haemoglobin oxidation. Only dapsone was active here. HPLC analyses suggested that the drugs were not significantly metabolized in the MPO-H2O2 system in the absence of Cl-. Bleaching of clofazimine was stimulated by Cl- in the MPO system, suggesting the involvement of HOCl. Clofazimine was found to be a more potent scavenger of HOCl than dapsone when the inhibition of NADH oxidation by reagent HOCl was used as an assay. This finding is also supported by HPLC analyses which indicated a greater sensitivity of HOCl for clofazimine than for dapsone. Relatively low concentrations of dapsone inhibited the oxidation of oxygenated haemoglobin (HbO2), suggesting that the drug was not metabolized to its N-hydroxylated derivative which is thought to be responsible for methaemoglobin (metHb) formation in vivo. It is proposed that the inhibitory mechanism of action of clofazimine is to scavenge chlorinating oxidants generated by the MPO-Cl(-)-H2O2 system, while dapsone converts MPO into its inactive compound II (ferryl) form. The different inhibitory mechanisms of clofazimine and dapsone towards the MPO system may contribute to the anti-inflammatory actions of the drugs.

Natural human monocyte gelatinase and its inhibitor

Gelatinases produced by stimulated peripheral blood monocytes were detected by substrate zymography and were compared with those derived from tumor cells. Stimulated monocytes were found to produce an 85 kDa gelatinase which co-migrated upon electrophoretic separation and cross-reacted in immunoprecipitation experiments with a phorbol ester inducible metalloprotease from human tumor cells. The intact natural gelatinase (85 kDa), a high molecular weight and complexed gelatinase as well as a proteolytic fragment (25 kDa) were purified by substrate- and antibody-affinity chromatography techniques. Aminoterminal sequence analysis showed that natural monocyte gelatinase occurs as a truncated form of tumor cell gelatinase/type IV collagenase. Furthermore, peripheral blood monocytes were found to also produce a tissue inhibitor of metalloproteases (TIMP). TIMP was co-purified with gelatinase on gelatin sepharose and identified by microsequencing. The balanced and regulated production of gelatinase and TIMP might be important in monocyte migration and tissue remodeling.

Identification of an abundant latent 94-kDa gelatin-degrading metalloprotease in human saliva which is activated by acid exposure: implications for a role in digestion of collagenous proteins

Human saliva was found to contain a latent neutral 94-kDa metalloprotease which degrades denatured collagens. Saliva samples from six normal resting individuals contained an average of 0.34 microgram/ml of latent enzyme. The 94-kDa salivary metalloprotease was found to bind to gelatin and to be immunologically identical to a leukocyte-derived 94-kDa gelatinase/type IV collagenase proenzyme. Exposure of the latent enzyme to acidic conditions (pH 2) followed by neutralization resulted in activation of the proenzyme. The activated enzyme degrades denatured collagens such as gelatin. Since 1-2 liters of saliva is swallowed per day and exposed to gastric acidity, this enzyme could become activated in the gastric compartment and following neutralization in the small bowel, may contribute to the degradation of ingested collagenous proteins.

Oxygen radicals, inflammation, and arthritis: pathophysiological considerations and implications for treatment

A vast amount of circumstantial evidence implicates oxygen-derived free radicals, especially superoxide and hydroxyl radical (and to lesser extent, hydrogen peroxide), as mediators of inflammation and/or tissue destruction in inflammatory and arthritic disorders. The substrates for radical generation, namely properly stimulated phagocytic cells, transition metal catalysts, and (to a limited extent) ischemia, are all amply present, although there is no particular rheumatic disease in which a consistent abnormality of radical generation has been identified. These radical species can clearly degrade hyaluronic acid, modify collagen and perhaps proteoglycan structure and/or synthesis, alter and interact with immunoglobulins, activate enzymes and inactivate their inhibitors, and possibly participate in chemotaxis. In most situations, however, there is ample scavenging ability to detoxify these radicals before they hit their target, and many rheumatic disease drugs can decrease their production and/or effects. Despite the apparent sufficiency of natural scavengers and the lack of direct evidence that oxygen radicals are pathogenetically important, substantial pharmaceutical effort is still being made to develop free radical scavengers as therapeutic agents. Although individual free radicals die out quickly, rheumatologic interest in them has been sustained for nearly two decades.

Intracellular and extracellular enzymatic deacylation of bacterial endotoxin during localized inflammation induced by Escherichia coli

Acyloxyacyl hydrolase (AOAH), an enzyme that removes the secondary acyl chains of gram-negative bacterial lipid A (endotoxin), has been identified previously in human neutrophils and mouse macrophages. We report here that bovine leukocytes also contain AOAH activity. Although bovine AOAH deacylates bacterial lipopolysaccharide in a manner similar to human AOAH, it is active in vitro over a broader pH range, from 4.0 to 7.0. By using Escherichia coli infection of the bovine mammary gland as a model of localized gram-negative bacterial disease and associated tissue inflammation, AOAH activity per leukocyte increased. In addition, AOAH activity increased in the cell-free portion of infected mammary secretions. These data indicate that AOAH activity increases in leukocytes associated with inflammation induced by gram-negative bacteria and provide additional evidence of its potential involvement in the defense against the effects of bacterial endotoxin.

Suppression of human neutrophil functions by tetracyclines

Tetracycline inhibition of neutrophil-associated collagenolysis has been the focus of a number of investigations. Evidence has suggested that this inhibition results from the ability of this family of antimicrobial drugs to bind divalent cations such as Ca2+ and Zn2+, two cations that are required for full expression of activity of metalloproteinases such as collagenase and gelatinase. Data presented in this study demonstrate that tetracyclines can also inhibit neutrophil-mediated RBC lysis, superoxide anion synthesis, degranulation and migration. To some extent, tetracycline inhibition of neutrophil functions is mimicked by the Ca2+ binding agents, EDTA and TMB-8. However, Ca2+ enrichment restored full function to EDTA- and TMB-8-treated cells but not to tetracycline-treated neutrophils. This suggests that Ca2+ binding plays a role but is not the critical effect leading to tetracycline suppression of neutrophil functions. It has been suggested that tetracyclines can suppress leukocyte-associated tissue damage. Host tissues are protected from neutrophil-mediated damage by two mechanisms: 1. Neutrophil granule-associated enzymes are secreted in an inactive state; and, 2. tissues are protected from these enzymes by a potent inhibitor shield. Neutrophils can bypass these protective elements by activating enzymes and by destroying the shield through the synthesis of oxygen radicals. Therefore, tetracyclines may suppress neutrophil-mediated tissue damage by inhibiting their migration and degranulation and, potentially more importantly, by suppressing synthesis of oxygen radicals.(ABSTRACT TRUNCATED AT 250 WORDS)

Characterization and activation of procollagenase from human polymorphonuclear leucocytes. N-terminal sequence determination of the proenzyme and various proteolytically activated forms

Procollagenase of human polymorphonuclear leucocytes was purified to homogeneity using a rapid and reproducible method. The purification procedure included affinity chromatography on zinc chelate Sepharose, ion exchange chromatography on Q-Sepharose fast flow, followed by affinity chromatography on orange Sepharose and finally a gel-permeation step on Sephacryl S-300. It was shown by SDS/PAGE, under reducing conditions, that the latent collagenase of human polymorphonuclear leucocytes consists of a single polypeptide chain with an apparent relative molecular mass of 85,000. Upon deglycosylation by endoglycosidase F digestion, the apparent relative molecular mass of the procollagenase was reduced to 53,000 which is similar to that of the fibroblast enzyme, and indicates a close relationship between both enzymes. Sequence data were determined by direct automated Edman degradation of the purified polymorphonuclear leucocyte procollagenase. The complete sequence of the propeptide region (residue 1-120) was thereby established. The proteolytic activation of the polymorphonuclear leucocyte procollagenase by various enzymes was investigated by determining the N-terminal sequences of the intermediate and final activated forms. Activation by chymotrypsin and cathepsin G led to the active form (Mr 64,000) by cleaving 79 N-terminal residues from the proenzyme. Trypsin activates in a two-step process. Cleavage of 48 N-terminal residues led to a still latent Mr 70,000 species. The final active form (Mr 65,000) was obtained by splitting off 20 additional N-terminal residues.

Apparent inactivation of alpha 1-antiproteinase by sulphur-containing radicals derived from penicillamine

alpha 1-Antiproteinase is the major inhibitor of proteolytic enzymes, such as elastase, in human plasma. Its elastase-inhibitory capacity can be inactivated by exposure to hydroxyl radicals (.OH) generated either by pulse radiolysis or by an Fe3+-EDTA/H2O2/ascorbic acid system. Inactivation of alpha 1-antiproteinase by radiolytically-generated .OH under anoxic conditions was decreased by adding a range of anti-inflammatory drugs to the reaction mixtures, including the thiol compound penicillamine. However, under conditions favouring formation of oxysulphur radicals, protection by thiols such as penicillamine was much decreased. It is proposed that sulphur-containing radicals resulting from attack of biologically-produced oxidants upon penicillamine in the presence of O2 can themselves inactivate alpha 1-antiproteinase, and that such radicals might contribute to the side-effects produced by penicillamine or gold thiol therapy in rheumatoid arthritis.

Disruption of the subendothelial basement membrane during neutrophil diapedesis in an in vitro construct of a blood vessel wall

To examine the course of physiologic interactions between extravasating neutrophils and the subendothelial basement membrane, a model of the venular vessel wall was constructed by culturing human umbilical vein endothelial cells on a collagen matrix. After 21 d in culture, the endothelial cell monolayer displayed in vivo-like intercellular borders and junctions, deposited a single-layered, continuous basement membrane that was impenetrable to colloidal particles, and supported neutrophil extravasation in a physiologic manner. Using this model, we demonstrate that neutrophil transmigration in a plasma milieu was associated with a significant disruption of the retentive properties of the basement membrane in the absence of discernable morphologic changes. The loss of basement membrane integrity associated with neutrophil diapedesis was not dependent on neutrophil elastase or cathepsin G and was resistant to inhibitors directed against neutrophil collagenase, gelatinase, and heparanase. Despite the fact that this loss in matrix integrity could not be prevented, basement membrane defects were only transiently expressed before they were repaired by the overlying endothelium via a mechanism that required active protein and RNA synthesis. These data indicate that neutrophil extravasation and reversible basement membrane disruption are coordinated events that occur as a consequence of vessel wall transmigration.

Protection against tissue damage in vivo by desferrioxamine: what is its mechanism of action?

Desferrioxamine (deferoxamine) is an inhibitor of iron-dependent free radical reactions that has been used to investigate the role of such reactions in several animal model systems for human disease. In vitro, desferrioxamine is not only an iron chelator but also binds other metal ions, reacts with superoxide and hydroxyl radicals, affects eicosanoid synthesis, can act as a substrate for peroxidases and can generate a reactive nitroxide radical. However, considerations of desferrioxamine concentration in vivo suggest that its ability to inhibit iron-dependent free radical reactions is the major factor that accounts for desferrioxamine's generally-protective action in animal models of human disease.

The inhibitory effect of acetaminophen on the myeloperoxidase-induced antimicrobial system of the polymorphonuclear leukocyte

Acetaminophen binds via its acetamido side chain to purified myeloperoxidase in a pH-dependent manner and maximum binding occurred around pH 6. The H2O2-dependent myeloperoxidase-catalysed polymerization products of acetaminophen had excitation maxima at 304 nm and 334 nm in acid and alkaline solutions, respectively, and an intense blue fluorescence maximum at 426 nm. Acetaminophen can compete effectively with Cl- as myeloperoxidase substrate and thus HOCl formation is suppressed while HOCl, nevertheless present, can be scavenged by the drug. In this way the microbicidal action of the myeloperoxidase-H2O2-Cl- system can be seriously limited in the presence of high concentrations of acetaminophen. To study the effect of acetaminophen on peptide bond splitting in the myeloperoxidase antimicrobial system, thyroglobulin was used as a model peptide. Peptide bond splitting was inhibited at acetaminophen concentrations below the accepted toxic range for plasma values.

Action of hypochlorous acid on the antioxidant protective enzymes superoxide dismutase, catalase and glutathione peroxidase

The neutrophil enzyme myeloperoxidase generates hypochlorous acid (HOCl) at sites of inflammation. Glutathione peroxidase is very quickly inactivated by low concentration of HOCl. Inactivation of catalase is also rapid, but requires higher HOCl concentrations and the haem appears to be degraded. Inactivation of bovine CuZn superoxide dismutase is slower. Hence superoxide dismutase should not be easily inactivated by HOCl at sites of inflammation, which may contribute to its effectiveness as an anti-inflammatory agent and in minimizing reperfusion injury.