Degradation in vivo of articular cartilage in rheumatoid arthritis by leucocyte elastase from polymorphonuclear leucocytes

Macrophages in the synovial lining niche initiate neutrophil recruitment and articular inflammation

The first immune-activating changes within joint resident cells that lead to pathogenic leukocyte recruitment during articular inflammation remain largely unknown. In this study, we employ state-of-the-art confocal microscopy and image analysis in a systemic, whole-organ, and quantitative way to present evidence that synovial inflammation begins with the activation of lining macrophages. We show that lining, but not sublining macrophages phagocytose immune complexes containing the model antigen. Using the antigen-induced arthritis (AIA) model, we demonstrate that on recognition of antigen-antibody complexes, lining macrophages undergo significant activation, which is dependent on interferon regulatory factor 5 (IRF5), and produce chemokines, most notably CXCL1. Consequently, at the onset of inflammation, neutrophils are preferentially recruited in the vicinity of antigen-laden macrophages in the synovial lining niche. As inflammation progresses, neutrophils disperse across the whole synovium and form swarms in synovial sublining during resolution. Our study alters the paradigm of lining macrophages as immunosuppressive cells to important instigators of synovial inflammation.

C5a and C5aR are elevated in joints of rheumatoid and psoriatic arthritis patients, and C5aR blockade attenuates leukocyte migration to synovial fluid

Complement activation correlates to rheumatoid arthritis disease activity, and increased amounts of the complement split product C5a is observed in synovial fluids from rheumatoid arthritis patients. Blockade of C5a or its receptor (C5aR) is efficacious in several arthritis models. The aim of this study was to investigate the role of C5a and C5aR in human rheumatoid arthritis and psoriatic arthritis–both with respect to expression and function. Synovial fluid, blood and synovial samples were obtained from rheumatoid arthritis, psoriatic arthritis and osteoarthritis patients as a less inflammatory arthritis type, and blood from healthy subjects. Cells infiltrating synovial tissue were analysed by immunohistochemistry and flow cytometry. SF and blood were analysed for biomarkers by flow cytometry or ELISA. The effect of a blocking anti-human C5aR mAb on leukocyte migration was determined using a Boyden chamber. Appropriate statistical tests were applied for comparisons. C5aR⁺ cells were detected in most rheumatoid arthritis, in all psoriatic arthritis, but not in non-inflammatory control synovia. C5aR⁺ cells were primarily neutrophils and macrophages. C5aR⁺ macrophages were mainly found in lymphoid aggregates in close contact with T cells. C5a levels were increased in both rheumatoid arthritis and psoriatic arthritis synovial fluid compared to osteoarthritis, and in blood from rheumatoid arthritis compared to healthy subjects. Neutrophil and monocyte migration to rheumatoid arthritis synovial fluid was significantly inhibited by anti-C5aR. The data support that the C5a-C5aR axis may be driving the infiltration of inflammatory cells into the synovial fluid and synovium in both rheumatoid and psoriatic arthritis, and suggest that C5a or C5aR may be a promising treatment target in both diseases.

Biosensor analysis of the molecular interactions of pentosan polysulfate and of sulfated glycosaminoglycans with immobilized elastase, hyaluronidase and lysozyme using surface plasmon resonance (SPR) technology

Pentosan polysulfate (NaPPS) and chondroitin sulfates (ChSs) have recently been shown to exhibit both symptom and disease modifying activities in osteoarthritis (OA), but their respective mechanisms of action are still the subject of conjecture. Excessive catabolism of joint articular cartilage is considered to be responsible for the initiation and progression of OA but the abilities of these drugs to mitigate this process has received only limited attention. Human neutrophil elastase (HNE) is a proteinase, which can degrade the collagens and proteoglycans (PGs) of the cartilage directly or indirectly by activating latent matrix metalloproteinases. Hyaluronidase (HAase) is an endoglycosidase, which degrades glycosaminoglycans including hyaluronan, which provides the aggregating component of the PG aggrecan complex. In the present study the molecular interactions between the NaPPS, ChSs and some other sulfated polysaccharides with immobilized HNE, HAase or lysozyme (a cationic protein implicated in PG metabolism) were studied using a SPR biosensor device-BIAcore2000. The above three enzymes were covalently immobilized to a biosensor chip CM5 separately using amine coupling. The binding affinity of each sulfated polysaccharide and the kinetics of NaPPS over the concentration range of 0.3-5.0 microg/ml were determined. The inhibition of HNE by the sulfated polysaccharides as determined using the synthetic substrate succinyl-Ala-Ala-Val-nitroanilide (SAAVNA) in a functional assay was compared with their respective binding affinities for this proteinase using the BIAcore system. The results obtained with the two independent techniques showed good correlation and indicated that the degree and ring positions of oligosaccharide sulfation were major determinants of enzyme inhibitory activity. The observed difference in order of binding affinities of the drugs to the immobilized HNE, HAase and lysozyme suggests a conformational relationship, in addition to the charge interactions between the sulfate esters of the polysaccharides and the cationic amino acids of the enzymes. Significantly, the SPR biosensor technology demonstrated that small differences among sulfated polysaccharides, even subtle variations among different NaPPS batches, could be readily detected. The SPR technology therefore offers not only a sensitive and reproducible method for ranking noncompetitive enzyme inhibitors for drug discovery but a rapid and quantitative bioassay for monitoring batch consistency of manufacture.

A comparison of plasma polymorphonuclear leucocyte elastase levels in obese and lean individuals

Increased release of polymorphonuclear leucocyte (PMNL) elastase, when the PMNLs are activated, can damage tissues in vivo. It was postulated that PMNL elastase might have a tissue-remodelling effect in the body and that obese individuals might have less PMNL elastase activity than lean individuals. To test this hypothesis, plasma PMNL elastase levels were determined in 70 obese individuals and 30 lean normal controls. The PMNL elastase levels (determined by enzyme-linked immunosorbent assay) in the obese group (median 36.2 ng/ml) did not differ significantly from those in the lean healthy controls (32.6 ng/ml; P = 0.5).

Interleukin-1 receptor antagonist prevents expression of the metalloproteinase-generated neoepitope VDIPEN in antigen-induced arthritis

OBJECTIVE

To investigate the relationship between occurrence of the matrix metalloproteinase-generated neoepitope VDIPEN and proteoglycan (PG) loss in arthritis, and to examine the role of interleukin-1 (IL-1) in VDIPEN expression.

METHODS

VDIPEN expression was investigated in murine antigen-induced arthritis by immunolocalization studies on joint sections. The involvement of IL-1 in VDIPEN expression was studied by blocking of IL-1 using IL-1 receptor antagonist (IL-1Ra).

RESULTS

Profound PG loss was evident early in arthritis, without significant VDIPEN expression. Full expression of the neoepitope appeared after a few days, when PG depletion was severe, and disappeared at late stages when cartilage showed recovery from PG depletion. At sites where chondrocyte death occurred and cartilage did not recover from the initial cartilage depletion, VDIPEN expression remained present. Prophylactic IL-1Ra treatment of arthritic mice resulted in almost complete prevention of VDIPEN expression. However, IL-1Ra had only a minor effect on PG depletion, emphasizing that there is no correlation between VDIPEN and early PG depletion.

CONCLUSION

This study indicates that IL-1 is involved in VDIPEN expression. Although VDIPEN-inducing metalloproteinases do not seem to be involved in early PG depletion during antigen-induced arthritis, metalloproteinase neoepitopes are present when PG depletion is severe.

Antioxidant effects of hyaluronan and its alpha-methyl-prednisolone derivative in chondrocyte and cartilage cultures

OBJECTIVE

To compare hyaluronan and its alpha-methyl prednisolone derivative (HYC-141) with respect to their potential to directly cause tissue damage and to protect tissues from attack by reactive oxygen species.

METHODS

Cartilage samples and chondrocytes were isolated from 15-day chick embryos and were exposed to enzyme-based and activated inflammatory cell-free radical generating systems in the presence of varying concentrations of alpha-methyl prednisolone, hyaluronan, and HYC-141. Tissue and cell vitality was measured by determining the incorporation of radioactive sulphate into newly synthesized glycosaminoglycans.

RESULTS

Only alpha-methyl prednisolone caused a significant decrease in biosynthetic activity. All the tested substances were capable, to some extent, of protecting tissues and cells from damage by reactive oxygen species; HYC-141 demonstrated the greatest protective effect.

CONCLUSION

These data suggest that HYC-141 may possess certain advantages over the individual component molecules in the local treatment of arthropathies.

Comparison of the proteoglycanolytic activities of human leukocyte elastase and human cathepsin G in vitro and in vivo

In this study, we evaluated the in vitro and in vivo potency of human leukocyte elastase (HLE) and human cathepsin G (HCG) as proteoglycanases. In vitro evaluation was done using bovine nasal septum aggrecan and aggrecan/hyaluronan aggregate as substrates. Enzyme activity was assessed by the ability of the proteinases to abrogate the ability of aggrecan to aggregate with hyaluronan. In vivo activity of the proteinases was tested by injecting purified HLE and HCG intra-articularly into rabbit stifle joints and quantifying the levels of proteoglycan released into synovial fluids. On a molar basis, HCG was at least tenfold more potent than HLE as a proteoglycanase in vitro. Moreover, HCG was twofold more potent as a proteoglycanase in vivo. In contrast, HLE hydrolyzed elastin approximately 22-fold faster than HCG, but was only slightly more rapid than HCG when [3H]-transferrin was used as substrate. These data indicate that HCG is more potent than HLE as a proteoglycanase both in vitro and in vivo. Thus, HCG could be more important in the pathogenesis of rheumatoid arthritis than previously suspected.

Recombinant human interleukin-1 beta-induced increase in levels of proteoglycans, stromelysin, and leukocytes in rabbit synovial fluid

OBJECTIVE

To evaluate the effects of intraarticular injection of recombinant human interleukin-1 beta (IL-1 beta) on levels of proteoglycans, stromelysin, and leukocytes in rabbit synovial fluid (SF), and to determine the effects of leukocyte depletion on SF proteoglycan and stromelysin levels.

METHODS

Levels of leukocytes and of proteoglycans, stromelysin, and collagenase were evaluated 12 hours after the intraarticular injection of various doses of IL-1, and over a 24-hour period after injection at a single dose level. We used a monoclonal antibody (MAb) against leukocyte integrins, which markedly depressed leukocyte accumulation in SF, to evaluate the role of synovial leukocytes on IL-1-induced increases in SF proteoglycan and stromelysin levels.

RESULTS

Levels of both proteoglycans and stromelysin increased in the IL-1-injected joints between 4 hours and 24 hours after the injection of a single 200-ng dose of IL-1. The highest levels of stromelysin and proteoglycans were achieved with IL-1 doses greater than or equal to 100 ng. Infiltration of polymorphonuclear cells (PMN) into the joint fluid of the IL-1-injected rabbits also increased, in a dose-dependent manner. Treatment of rabbits with MAb 1B4 markedly reduced infiltration of PMN into the joint, without affecting either stromelysin or proteoglycan levels.

CONCLUSION

Taken together, the data suggest that there is a coordinate increase in SF stromelysin and proteoglycan levels in rabbits injected with IL-1, and that leukocytes play a minimal role in the accumulation of proteoglycans and stromelysin in the SF.

Induction of neutrophil-mediated cartilage degradation by interleukin-8

Neutrophil influx into the inflamed joint is a characteristic feature of disease flares in patients with rheumatoid arthritis. Recently, a protein produced by monocytes and fibroblasts that has chemoattractive/activating properties for neutrophils has been identified and characterized. This protein has been called interleukin-8 (IL-8). In this study, we cocultured neutrophils with 35S-sulfate-labeled cartilage and found that the addition of recombinant human IL-8 (rHuIL-8) caused rapid, neutrophil-mediated cartilage degradation that was the result of induction of neutrophil degranulation by the cytokine. With 10(-7)M rHuIL-8, 23% of the radiolabel was released into the culture medium in 4 hours, compared with a 9% release without the factor. At concentrations of up to 10(-6)M, rHuIL-8 had no direct effect upon cartilage breakdown. These findings indicate that IL-8 may participate in the pathogenesis of rheumatoid arthritis through the induction of neutrophil-mediated cartilage damage.

The oxidant hypochlorite (OCl-), a product of the myeloperoxidase system, degrades articular cartilage proteoglycan aggregate

The myeloperoxidase-derived oxidant, hypochlorite (OCl-) was shown to be able to degrade proteoglycan aggregate prepared from bovine articular cartilage. Exposure of proteoglycan aggregate to OCl- concentrations less than 10(-4) M resulted in a decrease in the size of the constituent proteoglycan monomers, which were unable to reaggregate with hyaluronate due to the loss of the hyaluronic acid binding region as indicated by immunoblotting using the monoclonal 1-C-6 antibody. Analysis of the [35S]-labeled core proteins by SDS/polyacrylamide electrophoresis and fluorography indicated a decrease in the size of the core protein. These data suggest that concentrations of OCl- below 10(-3) M results in the cleavage of the proteoglycan core protein in or near the hyaluronic acid binding region. The physiological consequences of these data are discussed. Exposure to higher concentrations (greater than 10(-3)) of OCl- caused more extensive degradation of the core protein; however, there was no evidence to suggest that OCl- cleaves glycosaminoglycan (GAG) chains.

Antigen induced arthritis in beige (Chediak-Higashi) mice

Mice with the beige mutation, which are known to be deficient for leucocyte elastase and cathepsin G, were used to investigate the role of neutral proteases in a model for antigen induced arthritis. Surprisingly, it was shown that in this model of arthritis, using methylated bovine serum albumin as an antigen, C57/black/6 'beige' mice (deficient for leucocyte neutral proteases) developed a more severe form of arthritis than the control mice ('black' mice), resulting in a higher degree of tissue damage. The incidence and degree of bone apposition and destruction of articular cartilage at day 21 after induction of arthritis were significantly higher in the beige mice. These findings could not be ascribed to differences in the cellular immune response to methylated bovine serum albumin. Autoradiographic detection of radiolabelled methylated bovine serum albumin suggested that more antigen is retained in the joints of beige mice than in black mice, which might account for the sustained arthritis and the concomitant tissue damage. These findings do not support the contention that leucocyte elastase and cathepsin G contribute to the pathogenesis of joint destruction in this model.

Mechanisms of bone degradation in infection: a review of current hypotheses

Bone infection in clinical practice results in loss of structural integrity, leading to complications such as fracture and implant loosening. The biology of this process has received relatively little attention. In experimental models it seems clear that both polymorphonuclear leukocytes, whose effect predominates in the early stages, and mononuclear phagocytes are capable of bone degradation. An indirect effect by stimulation of physiologic mechanisms of resorption has not been ruled out, but the evidence points to direct degradation by inflammatory cell enzymes.

Neutrophil-mediated cartilage injury in vitro is enhanced by tumour necrosis factor alpha

Neutrophil functions relevant to tissue damage are altered by cytokines such as tumour necrosis factor alpha (cachectin, TNF alpha), known to be present in inflammatory foci. In this study we examined the effect of TNF alpha on neutrophil-mediated cartilage damage in vitro. Human neutrophils were able to injure both human and bovine articular cartilage slices by degrading proteoglycan and inhibiting its synthesis. Recombinant human TNF alpha enhanced neutrophil-mediated degradation of proteoglycan, even when neutrophils were preincubated with TNF alpha and washed before incubating with cartilage. TNF alpha alone degraded proteoglycan and inhibited its synthesis. Neutrophil-mediated inhibition of proteoglycan biosynthesis was increased after incubating cartilage together with neutrophils and TNF alpha, but was unaltered when neutrophils were preincubated with TNF alpha. We conclude that TNF alpha enhances neutrophil injury to articular cartilage.

Hydantoin derivatives. A new class of inhibitors of human leukocyte elastase

Derivatives of hydantoin have been found to inactivate human leukocyte elastase irreversibly. Chymotrypsin and cathepsin G are also inhibited by these compounds.

Circulating neutrophil elastase in infectious diseases in geriatric patients

Enzyme-linked immunosorbent assay has been used to measure elastase proteinase inhibitor complex (EPIC) and C-reactive protein (CRP) in the elderly, with and without infection. Median EPIC levels in the elderly with infection, hospital controls, healthy elderly residents in old people's homes and healthy blood donors were 300, 104, 96 and 74 ng/ml respectively. Ninety-five per cent of the patients with infection had EPIC levels well above the normal range. The median EPIC level in the elderly with infection showed a statistically significant difference from that in the control groups (p less than 0.0001, Mann U test). CRP showed similar results. Elevation of EPIC or CRP did not depend on the type of infection or bacteria isolated. We would conclude that neutrophil inhibitor-bound elastase could be used as a marker of inflammation in old people.

Effect of piroxicam therapy on granulocyte function and granulocyte elastase concentration in peripheral blood and synovial fluid of rheumatoid arthritis patients

The effect of piroxicam therapy (20 mg/day for 15 days) on various polymorphonuclear granulocyte (PMN) responses and on PMN elastase concentration was investigated in nine patients with active rheumatoid arthritis. Peripheral blood and synovial fluid samples were collected before starting therapy and 12 h after the last dose of the drug. All patients were evaluable for peripheral blood analysis and six for synovial fluid analysis. Piroxicam therapy had no effect on PMN random migration and phagocytosis, while it significantly reduced both FMLP-induced aggregation and FMLP-induced chemotaxis. This seems mainly due to an effect on FMLP binding, as no differences were observed after therapy in PMA- and PHA-induced aggregation as well as in serum-induced chemotaxis. In contrast, a marked impairment of NBT test and PMA- and FMLP-induced superoxide anion (O2-) production was found after piroxicam therapy. This effect was as evident in peripheral blood as in synovial fluid PMN. Also, a significant reduction in synovial fluid PMN number and synovial fluid PMN elastase concentration (elastase-alpha 1-proteinase complex) was found after treatment. It is concluded that piroxicam may act at different sites on various PMN responses. Its effect on O2- generation and PMN elastase concentration in synovial fluid may have an important role in reducing destruction of arthritic joint tissue.

Tumour necrosis factor-beta modulates human neutrophil-mediated cartilage damage

Human neutrophils, when cultured with human articular cartilage coated with heat-aggregated immunoglobulin G, degraded proteoglycan and inhibited its synthesis. Neutrophil-mediated degradation of cartilage was potentiated by recombinant human tumour necrosis factor-beta (TNF beta), although TNF beta alone did not alter proteoglycan degradation. This effect was seen when TNF beta, neutrophils, and cartilage were incubated together, and also when neutrophils were preincubated with TNF beta and washed before being added to cartilage. Similar results were obtained with living and killed cartilage. In contrast, pretreatment of neutrophils with TNF beta abrogated the neutrophil-mediated inhibition of proteoglycan biosynthesis. There was no effect of TNF beta alone on synthesis of proteoglycan.

Conditioned medium from stimulated mononuclear leucocytes potentiates the ability of human neutrophils to damage human articular cartilage

Human neutrophils were able to degrade proteoglycan and inhibit its synthesis when incubated with human articular cartilage coated with heat aggregated immunoglobulin G. These effects were potentiated when culture medium conditioned by mononuclear leucocytes stimulated with killed Staphylococcus aureus was also present during the incubations. Neutrophils preincubated with this conditioned medium and washed before incubation with cartilage also showed an increased ability to degrade proteoglycan and inhibit its synthesis. The percentage of neutrophils binding to cartilage was significantly increased in the presence of this conditioned medium.

Degradation of cartilage proteoglycans by elastase is dependent on charge-mediated interactions

We investigated the mechanism of cartilage degradation by pancreatic elastase as a model system for the action of cationic proteases such as leukocyte elastase and cathepsin-G. It is shown that the cationic properties of elastase contribute to its proteolytic potential with respect to cartilage degradation. Elastase preparations with neutral or negative charge, obtained by chemical modification were far less effective in cartilage degradation than the cationic, native enzyme. Modification of elastase did not affect the active site of the enzyme as shown by kinetic studies, nor did it alter the complexing with alpha-1-proteinase inhibitor. Quantitative and autoradiographic studies indicate that the positive charge of the enzyme favors the penetration in cartilage and interaction with the polyanionic proteoglycan substrate. It is concluded that the potent cartilage-degrading activity of elastase is dependent on charge-mediated interactions with its substrate.

Interference of cartilage surface with interaction of granulocyte elastase with alpha 1-proteinase inhibitor. An in vitro model of enzyme inhibition in the joint space

Synovial fluids of patients suffering from rheumatoid arthritis contain elevated levels of granulocyte (PMN) elastase in complex with alpha 1-proteinase inhibitor (alpha 1-PI), whereas free-elastase activity is usually not detectable. This absence of free enzymatic activity in joint effusions has cast some doubt on the pathophysiological relevance of PMN elastase in inflammatory joint destruction. Our in vitro experiments using bovine nasal cartilage demonstrate that incubation with elastase and alpha 1-PI in equimolar concentrations to or even in excess of the serum proteinase inhibitor resulted in significant tissue destruction as assessed by histological staining for proteoglycans, release of uronic acid from the matrix and loss of mechanical stability. Though in the supernatants containing alpha 1-PI, free-elastase activity was not detectable, immunofluorescent staining for elastase evidenced penetration of the enzyme into the matrix. Simultaneous measurements of the incubation media employing a sandwich enzyme-linked immunoadsorption assay (ELISA) revealed PMN elastase in complex with alpha 1-PI but without correlation to the parameters of tissue degradation. In comparison with the results obtained using the chromogenic substrate Suc-Ala-Ala-Ala-pNA (SAPA) for titration of alpha 1-PI against elastase, the employment of cartilage matrix showed that a fourfold increase in inhibitor concentration was necessary to achieve 100% enzyme inhibition. Hence, cartilage surface obviously interferes with the interaction between alpha 1-PI and elastase. Measurements of elastase-inhibitor concentrations or free enzymatic activity in synovial fluid seem to have limited value in predicting cartilage destruction.

Receptor-mediated binding of leukocyte elastase by chondrocytes

Studies on the effect of leukocyte elastase on the metabolism of chondrocytes in culture have demonstrated that these cells possess a specific cell surface receptor for leukocyte-derived elastase. Purified elastase from rabbit and human leukocytes is capable of modulating the metabolism of the cell by causing a marked decrease in both proteoglycan and protein biosynthesis. Addition of 125I-labeled elastase to chondrocytes maintained in suspension culture has shown that binding occurs, and that it is saturable and is inhibited by the addition of unlabeled enzyme. We ascertained that the active site of the enzyme was necessary for binding to the chondrocyte, since phenylmethylsulfonyl fluoride-inactivated leukocyte elastase failed to bind. Pancreatic elastase had only a slight affinity for the receptor, whereas trypsin and bovine serum albumin failed to bind to any significant extent. Autoradiographic studies and the use of inhibitors of endocytosis, such as dansyl cadaverine, confirmed that endocytosis of elastase was the secondary event after cell binding.

Degradation in vivo of articular cartilage in rheumatoid arthritis and juvenile chronic arthritis by cathepsin G and elastase from polymorphonuclear leukocytes

Peroxidase-anti-peroxidase (PAP) staining and specific antibodies against cathepsin G and elastase from polymorphonuclear leukocytes (PMN) were applied to pannus-free and microscopically intact superficial articular cartilage. Restricted local deposits containing cathepsin G and elastase were found in three of ten patients with seropositive rheumatoid arthritis (RA), in one of three patients with seronegative RA and in one patient with juvenile chronic arthritis (JCA). Similarly, localized deposits of IgG and C3 were found in the patients with seropositive RA and JCA, but not in the patient with seronegative RA. Adjacent sections exhibited esterase activity in and around the PMN. In proteinase-positive areas from patients with seropositive RA the inhibitors alpha 1-proteinase inhibitor (alpha 1-PI) and alpha 2-macroglobulin (alpha 2-MG) were present in two of three and one of three patients, respectively. In JCA only alpha 1-proteinase inhibitor was present, and in seronegative RA no inhibitors were found. No staining of articular cartilage was observed in a patient with psoriatic arthritis. One of three cases with osteoarthritis exhibited patchy superficial staining for IgG only. In articular cartilage covered by pannus, in three patients with seropositive RA, in one with seronegative RA and in the patient with JCA a few regions with variably dense PMN infiltrates were observed. Cathepsin G, elastase and esterase activity were found in and around the PMN. In one of the three patients with seropositive RA the adjacent cartilage-pannus junction exhibited distinct staining for cathepsin G and elastase, but not for IgG/C3 and proteinase inhibitors.(ABSTRACT TRUNCATED AT 250 WORDS)

Cephalosporin antibiotics can be modified to inhibit human leukocyte elastase

Several laboratories, including our own have reported the synthesis and activity of certain low relative molecular mass inhibitors of mammalian serine proteases, especially human leukocyte elastase (HLE, EC 3.4.21.37), an enzyme whose degradative activity on lung elastin has been implicated as a major causative factor in the induction of pulmonary emphysema, and which is present in the azurophil granules of human polymorphonuclear leukocytes (PMN). Normally, these granules fuse with phagosomes containing engulfed foreign material (such as bacteria), and HLE, in combination with other lysosomal enzymes, catabolizes the particles. Under certain pathological conditions, however, PMN become attached to host protein (elastin fibres, basement membrane, connective tissue, immune complexes), and in response to this adherence, the granules may fuse with the PMN outer membrane and release their contents, including HLE, directly onto the tissue. Besides emphysema, HLE may also contribute to the pathogenesis of disease states such as adult respiratory distress syndrome, and its potential involvement in rheumatoid arthritis makes HLE inhibitors of considerable interest. It is known that cephalosporin antibiotics (for example, cephalothin (compound I, Table 2)) are acylating inhibitors of bacterial serine proteases which help synthesize the cell wall by performing a transpeptidation reaction on a peptidyl substrate bearing a D-Ala-D-Ala terminus. We now report that neutral cephalosporins (that is, compounds not bearing a free carboxyl at position C-4) can be modified to become potent time-dependent inhibitors of HLE.

Oxygen radicals as effectors of cartilage destruction. Direct degradative effect on matrix components and indirect action via activation of latent collagenase from polymorphonuclear leukocytes

Degradation of intact cartilaginous tissue (bovine nasal cartilage) by oxygen-derived free radicals (ODFR) generated enzymatically by xanthine oxidase and hypoxanthine was studied. The degree of tissue destruction was determined by measuring the indentation under a defined compression force as well as by the loss of uronic acid- and hydroxyproline-containing matrix components. Cartilage slices altered by prior elastase treatment were more susceptible to oxygen radical attack than were intact tissue specimens. Degradation of cartilage matrix by ODFR was strongly inhibited by superoxide dismutase or catalase. Coincubation of latent collagenase from polymorphonuclear leukocytes with the ODFR-generating system led to activation of collagenolytic activity, resulting in marked degradation of the bovine cartilage slices. In further studies, activated polymorphonuclear leukocyte-collagenase was shown to degrade intact human articular cartilage to a degree of mechanical insufficiency. Thus, our assay system serves as an in vitro model of tissue damage, which may be relevant to pathophysiologic states such as rheumatoid arthritis.

Granulocyte elastase as a new biochemical marker in the diagnosis of chronic joint diseases

Human granulocyte elastase (EC 3.4.21.37) is released from granulocytes in large amounts in chronic inflammatory joint diseases and is therefore of special pathogenic and diagnostic importance. In order to examine the diagnostic significance of this enzyme as a clinico-chemical parameter, we determined the concentration of granulocyte elastase in complex with alpha 1-proteinase inhibitor by an enzyme immunoassay in synovial fluids and plasma of patients with chronic joint diseases. In inflammatory synovial fluids the concentration of complexed elastase correlates well with the granulocyte number and may increase to an extremely high level. In 90% of patients with manifest rheumatoid arthritis increased elastase levels are also observed in the plasma, probably due to the large gradient between the synovial fluid and plasma concentration, whereas in osteoarthrosis normal plasma concentrations were observed. Thus, these results indicate that normal plasma concentrations in patients with chronic joint diseases exclude the diagnosis of rheumatoid arthritis with high probability. The simultaneous determination of complexed elastase in plasma and synovial fluid improves the nosological differentiation of chronic joint diseases. Elastase activity on a specific chromogenic substrate, which was found in many inflammatory synovial fluids, is mainly attributed to elastase alpha 2-macroglobulin complexes. In some purulent synovial fluids, however, we were able to detect free elastase, which has been shown to play an important role in the destruction of articular cartilage.

Circulating human leucocyte elastase in rheumatoid arthritis

Elastase-inhibitor complex (EIC) levels were determined in EDTA-plasma samples of 40 patients with connective tissue disease by a double antibody immuno-assay technique. In active rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE), EIC levels were significantly higher than in the normal controls (P less than 10(-8) and fell on remission. The mean EIC level in active RA was significantly greater than in inactive disease (P = 0.0001) but there was no statistically significant difference between the EIC levels in the acute and inactive disease states in SLE (P = 0.49). In active RA, there was a positive correlation between EIC levels and white blood cell count (WBC) but not with erythrocyte sedimentation rate (ESR). In SLE there was no significant correlation between EIC levels and ESR or WBC. EIC measurement may be useful in the objective assessment of activity in RA.

Changes in proteoglycan biosynthesis following leukocyte elastase treatment of bovine articular cartilage in culture

Treatment of bovine articular cartilage in culture with a low molecular weight elastase purified from rabbit polymorphonuclear leukocytes resulted in degradation and release of proteoglycans from the tissue, coupled with a prolonged inhibition of proteoglycan biosynthesis. These observations are consistent with those seen in experimental arthritis induced in rabbits. Comparison of the size of the proteoglycan degradation products extracted from elastase-treated cartilage in culture with that from arthritic cartilage showed marked similarities. The results strongly suggest that leukocyte elastase is a contributing factor in proteoglycan degradation and inhibition of synthesis in inflammatory joint disease.

Study of enzyme inhibitors in the rheumatoid pannus-cartilage area

Immunoperoxidase studies were carried out on the pannus-cartilage junction (PCJ) of patients with rheumatoid arthritis (RA) and psoriatic arthritis to investigate the distribution of the enzyme inhibitors alpha 2 macroglobulin (alpha 2 M) and alpha 1 antitrypsin (alpha 1 AT). Comparisons were made with the equivalent synovial cartilage junctional area in osteoarthritis (OA). In all 12 patients with RA, prominent deposits of alpha 2 M and alpha 1 AT were found within the PCJ whereas in OA patients and the case of psoriatic arthritis fewer or no deposits were seen. Inhibitors were localised in pannus synovial lining cells, perivascular inflammatory cells, macrophage and fibroblast-like cells invading the cartilage as well as along the junctional cartilage matrix and in the adjacent pannus-free cartilage. Deposits of immunoglobulins were found in similar areas to enzyme inhibitors. The presence of enzyme inhibitors at the PCJ suggests that this area is not unprotected against enzymatic attack. Thus the concept that pannus is a prime area for cartilage damage because aggressive, invasive cells release destructive enzymes in an environment free from inhibitors should be reviewed.