The possible role of neutrophil proteinases in damage to articular cartilage

Synergistic Roles of Macrophages and Neutrophils in Osteoarthritis Progression

OBJECTIVE

To evaluate the role of immune cells and their effector cytokines in the pathogenesis and progression of knee osteoarthritis (OA) in matched OA synovial fluid (SF) and synovial tissue samples.

METHODS

Cells from matched samples of synovial tissue and SF acquired from individuals undergoing total knee replacement for OA (n = 39) were characterized for immune cell-associated surface markers and intracellular cytokine expression using polychromatic flow cytometry. Additional individuals with radiographic knee OA (Kellgren/Lawrence severity grades ≥1) who had available etarfolatide (inflammatory cell) imaging (n = 26) or baseline and 3-year data on progression of radiographic knee OA (n = 85) were also assessed. SF cytokine concentrations in all cohorts were evaluated for associations with synovial tissue and SF cell phenotypes and severity of radiographic knee OA.

RESULTS

Macrophages (predominant in the synovial tissue, 53% of total cells) and neutrophils (predominant in the SF, 26% of total cells) were the major immune cell populations identified in the OA knee joints, exhibiting expression of or association with transforming growth factor β1 (TGFβ1) and elastase, respectively, in the SF. Expression levels of TGFβ1 and elastase were significantly associated with severity of radiographic knee OA. Baseline SF concentrations of TGFβ1 and elastase along with radiographic knee OA severity scores were predictive of knee OA progression, with areas under the receiver operating characteristic curves of 0.810 (for TGFβ1), 0.806 (for elastase), and 0.846 (for both TGFβ1 and elastase combined), with greater stability of prediction when both markers were utilized.

CONCLUSION

Our findings demonstrate the hitherto underappreciated role of neutrophils in the sterile inflammatory process and progression of OA. Two soluble mediators, SF elastase and TGFβ1, are strong predictors of knee OA progression, reflecting a synergistic role of neutrophil and macrophage populations in the pathogenesis and worsening of OA that could potentially be utilized to identify patients who may have a greater risk of more rapid disease progression.

Effect of biofilms on recalcitrance of staphylococcal joint infection to antibiotic treatment

The pathogenesis of joint infections is not well understood. In particular, we do not know why these infections respond poorly to antibiotic treatment. Here we show that methicillin-resistant Staphylococcus aureus, a major cause of joint infections, forms exceptionally strong biofilmlike aggregates in human synovial fluid (SF), to an extent significantly exceeding biofilm formation observed in growth medium or serum. Screening a transposon bank identified bacterial fibronectin- and fibrinogen-binding proteins as important for the formation of macroscopic clumps in SF, suggesting an important role of fibrin-containing clots in the formation of bacterial aggregates during joint infection. Pretreatment of SF with plasmin led to a strongly reduced formation of aggregates and increased susceptibility to antibiotics. These results give important insight into the pathogenesis of staphylococcal joint infection and the mechanisms underlying resistance to treatment. Furthermore, they point toward a potential novel approach for treating joint infections.

Cathepsin B and cystatin C play an inflammatory role in gouty arthritis of the knee

BACKGROUND

To relate the expression of the matrix degrading proteinase cathepsin B and its endogenous inhibitor cystatin C in the synovial fluid (SF) to the clinical and laboratory variables of joint inflammation in gouty arthritis of the knee.

METHODS

Thirty-nine SF samples were obtained from inflamed knees of patients with acute gout. The levels of cathepsin B, cystatin C, urokinase-type plasminogen activator (uPA), soluble uPA receptor (suPAR) and PA inhibitor type-1 (PAI-1), activities of matrix metalloproteinase-2 (MMP-2) and MMP-9, and cell counts as well as local arthritis activity scores (LAS) were examined.

RESULTS

The increases of cathepsin B levels correlated with increased leukocyte and neutrophil counts, latent MMP-9 (pro-MMP-9) activities, uPA, suPAR and PAI-1 levels, and uPA/PAI-1 ratios. Increased cystatin C levels corresponded closely with increased LAS, leukocyte and neutrophil counts, pro-MMP-9 activities, uPA, suPAR and PAI-1 levels, and uPA/PAI-1 ratios. Moreover, there was a correlation between cathepsin B and cystatin C levels.

CONCLUSIONS

These results show a high correlation between the cathepsin B/cystatin C system and markers of joint inflammation in acute gout of the knee, demonstrating the pathologic role of cathepsin B and cystatin C in inflammation.

Cellular mechanisms of proteinase release from inflammatory cells and the degradation of extracellular proteins

Neutrophils and macrophages produce, store and release large amounts of various acid and neutral proteinases. The two main proteinases of neutrophils are elastase and cathepsin G. They are localized in the azurophil granules, together with proteinase 3 and the acid cathepsins B and D. In addition neutrophils contain collagenase in the specific granules, acid proteinases in the C-particles and plasminogen activator in organelles with the characteristics of secretory vesicles. The granule-bound proteinases are released during phagocytosis while plasminogen activator is apparently secreted. In macrophages, the acid hydrolases are bound to lysosomes while the neutral proteinases are confined to secretory vesicles. The main mechanism of enzyme release in macrophages is secretion. Lysosomal hydrolases are also released by phagocytosis. Enzyme secretion is a characteristic property of activated or inflammatory macrophages. Macrophages become activated after phagocytosis of certain particles and the metabolic burst appears to be an initial event in the activation process. The action of neutrophils and of purified elastase or plasmin on cartilage was tested. These experiments indicate that neutrophil-mediated degradation of cartilage proteoglycans is largely dependent on elastase.

Cytokine mRNA expression in synovial fluid of affected and contralateral stifle joints and the left shoulder joint in dogs with unilateral disease of the stifle joint

OBJECTIVE

To examine mRNA expression of cytokines in synovial fluid (SF) cells from dogs with cranial cruciate ligament (CrCL) rupture and medial patellar luxation (MPL) and determine mRNA expression for 3 joints (affected stifle, unaffected contralateral stifle, and left shoulder joints) in dogs with unilateral CrCL rupture.

SAMPLE POPULATION

29 stifle joints with CrCL rupture (29 dogs), 8 stifle joints with MPL (7 dogs), and 24 normal stifle joints (16 clinically normal dogs).

PROCEDURES

Immediately before reconstructive surgery, SF was aspirated from the cruciate-deficient stifle joint or stifle joint with MPL. Fourteen of 29 dogs had unilateral CrCL rupture; SF was also aspirated from the unaffected contralateral stifle joint and left shoulder joint. Those 14 dogs were examined 6 and 12 months after reconstructive surgery. Total RNA was extracted from SF cells and reverse transcription-PCR assay was performed to obtain cDNA. Canine-specific cytokine mRNA expression was determined by use of a real-time PCR assay.

RESULTS

Interleukin (IL)-8 and -10 and interferon-gamma expression differed significantly between dogs with arthropathies and dogs with normal stifle joints. For the 14 dogs with unilateral CrCL rupture, a significant difference was found for IL-8 expression. Before reconstructive surgery, IL-8 expression differed significantly between the affected stifle joint and left shoulder joint or contralateral stifle joint. Six months after surgery, IL-8 expression was significantly increased in the unaffected contralateral stifle joint, compared with the shoulder joint.

CONCLUSIONS AND CLINICAL RELEVANCE

No conclusions can be made regarding the role of the examined cytokines in initiation of CrCL disease.

Interleukin-8 mRNA expression in synovial fluid of canine stifle joints with osteoarthritis

The objective of this study was to examine and compare the presence of interleukin (IL)-8 mRNA in canine stifle osteoarthritis (OA) differing in etiopathogenesis. Synovial fluid (SF) samples were collected from 24 clinically normal stifle joints and 46 diseased stifle joints (32 stifle joints with cranial cruciate ligament rupture (CCLR), 2 joints with CCLR and patella luxation (PL), 7 joints with medial PL and 5 joints with primary OA). The samples were centrifuged to collect synovial fluid cells for RNA extraction. Reverse transcription polymerase chain reaction (RT-PCR) was performed to obtain cDNA from all samples. Canine IL-8 mRNA expression was determined using real time PCR. Synovial fluid glass smears were made of all samples and coloured with H&E for differential cell counts. All stifle joints were radiographed and graded for the severity of OA. Sixty-one percent (28/46) of the samples from canine stifle OA had IL-8 mRNA expression in contrast to 4% (1/24) in the control stifle joints. This difference in prevalence is highly significant. There were no statistically significant pairwise differences among the mean ranks of the various OA groups for the absolute amount of IL-8 mRNA expression. Neither was there a link between the severity of OA (determined by radiographic evaluation) and the presence of IL-8 in the SF nor any significant difference in the absolute amount of IL-8 between the different OA grades. No statistical difference was found in differential cell counts between IL-8-positive and -negative SF samples. IL-8 cannot be used as a specific joint disease marker since IL-8 expression is found in OA differing in etiopathogenesis. It might, however, relate to the ongoing inflammation within the joint.

Cartilage degradation by stimulated human neutrophils: elastase is mainly responsible for cartilage damage

Although neutrophilic granulocytes are assumed to contribute to cartilage degradation during rheumatic diseases, there is still a discussion whether reactive oxygen species (ROS) or proteolytic enzymes that are both released by the neutrophils are most relevant to cartilage degradation. To gain further insight into these processes, an in vitro approach to study the interaction between the products of stimulated neutrophilic granulocytes and cartilage was used: Neutrophils from the blood of healthy volunteers were treated with different stimulators (e.g., Ca(2+) ionophores) in order to induce degranulation. Supernatants of neutrophils were afterward incubated with thin slices of pig articular cartilage. Some experiments were also performed in the presence of selected enzyme inhibitors. Supernatants of cartilage were subsequently assayed by one- and two-dimensional high-resolution proton NMR spectroscopy, and the content of soluble carbohydrates in the supernatant was additionally determined by biochemical methods. The selective inhibition of elastase decreased most significantly the extent of cartilage degradation, whereas all other inhibitors had much smaller effects. These results were additionally confirmed by measuring the effect of isolated elastase on articular cartilage in the absence and presence of different inhibitors. It is concluded that elastase released [EC 3.4.21.37] by neutrophils is the most relevant enzyme for cartilage degradation.

Cartilage degradation by stimulated human neutrophils: reactive oxygen species decrease markedly the activity of proteolytic enzymes

BACKGROUND

Although neutrophilic granulocytes clearly contribute to cartilage degradation in rheumatic diseases, it is unclear if reactive oxygen species (ROS) or proteolytic enzymes are the most important components in cartilage degradation and how they interact.

RESULTS

Neutrophils were stimulated by chemicals conferring a different degree of ROS formation and enzyme release. Supernatants of neutrophils were incubated with thin slices of pig articular cartilage. Supernatants of cartilage were assayed by NMR spectroscopy, MALDI-TOF mass spectrometry and relevant biochemical methods. Stimulation conditions of neutrophils correlated well with the extent of cartilage degradation. Due to the release of different enzymes, cartilage degradation could be best monitored by NMR since mainly low-mass degradation products were formed. Astonishingly, the suppression of the formation of ROS resulted in decreased cartilage degradation.

CONCLUSION

ROS formed by neutrophils are not directly involved in cartilage degradation but influence the activity of proteolytic enzymes, which are the main effectors of cartilage degradation.

Secretory leukocyte protease inhibitor suppresses the inflammation and joint damage of bacterial cell wall-induced arthritis

Disruption of the balance between proteases and protease inhibitors is often associated with pathologic tissue destruction. To explore the therapeutic potential of secretory leukocyte protease inhibitor (SLPI) in erosive joint diseases, we cloned, sequenced, and expressed active rat SLPI, which shares the protease-reactive site found in human SLPI. In a rat streptococcal cell wall (SCW)-induced model of inflammatory erosive polyarthritis, endogenous SLPI was unexpectedly upregulated at both mRNA and protein levels in inflamed joint tissues. Systemic delivery of purified recombinant rat SLPI inhibited joint inflammation and cartilage and bone destruction. Inflammatory pathways as reflected by circulating tumor necrosis factor alpha and nuclear factor kappaB activation and cartilage resorption detected by circulating levels of type II collagen collagenase-generated cleavage products were all diminished by SLPI treatment in acute and chronic arthritis, indicating that the action of SLPI may extend beyond inhibition of serine proteases.

Human cathepsin K cleaves native type I and II collagens at the N-terminal end of the triple helix

Cathepsin K (EC 3.4.22.38) is a recently described enzyme that has been shown to cleave type I collagen in its triple helix. The aim of this study was to determine if it also cleaves type II collagen in the triple helix and to identify the helical cleavage site(s) in types I and II collagens. Soluble human and bovine type II collagen, and rat type I collagen, were incubated with cathepsin K before the reaction was stopped with trans-epoxysuccinyl-l-leucylamido-(4-guanidino)butane (E-64). Analysis by SDS/PAGE of the collagen digests showed that optimal activity of cathepsin K against native type II collagen was between pH 5.0 and 5.5 and against denatured collagen between pH 4.0 and 7.0. The enzyme cleaved telopeptides as well as the alpha1(II) chains, generating multiple fragments in the range 90-120 kDa. The collagenolytic activity was not due to a contaminating metalloenzyme or serine proteinase as it was not inhibited by 1,10-phenanthroline, EDTA or 3,4-dichloroisocoumarin. Western blotting with anti-peptide antibodies to different regions of the alpha1(II) chain suggested that cathepsin K cleaved native alpha1(II) chains in the N-terminal region of the helical domain rather than at the well-defined collagenase cleavage site. This was confirmed by N-terminal sequencing of one of the fragments, revealing cleavage at a Gly-Lys bond, 58 residues from the N-terminus of the helical domain. By using a similar approach, cathepsin K was found to cleave native type I collagen close to the N-terminus of its triple helix. These results indicate that cathepsin K could have a role in the turnover of type II collagen, as well as type I collagen.

Elastase from polymorphonuclear leukocyte in articular cartilage and synovial fluids of patients with rheumatoid arthritis

Objective was to study the significance and the mechanism of action of elastase from polymorphonuclear leukocyte (PMN elastase) in patients with rheumatoid arthritis (RA). The experiments conducted consisted of two phases. Firstly, articular cartilage and synovia from 8 patients with RA undergoing total knee replacement were obtained, and the gelatinolytic enzyme activity was extracted with 2M guanidine hydrochloride. The gelatinolytic activity of each tissue was measured to confirm that the activity was due to PMN elastase by using an antihuman leukocyte elastase antibody. Secondly, the levels of PMN elastase-alpha 1 proteinase inhibitor complex (EIC) in the blood and synovial fluid of 170 patients with RA were measured by immunoassay. The results were as follows: 1. Gelatinolytic activity was shown to be mainly due to PMN elastase, and found to be highest in cartilage and synovia in RA joints. 2. The EIC levels in plasma of RA patients were significantly higher than those in gout and osteoarthritis (OA), and the EIC levels increased according to the stage of articular cartilage destruction. Moreover, the EIC levels in synovial fluid of RA patients were higher compared to those of OA patients. The activity of PMN elastase was elevated in destructive joints of RA. With the progression of articular cartilage destruction, EIC levels in plasma of RA patients increased as well. We suggest that PMN elastase may play a significant role in RA disease.

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.

An immunohistochemical study of collagen types III, VI and IX in rabbit craniomandibular joint tissues following surgical induction of anterior disk displacement

The purpose of this study was to determine the effect of surgical induction of anterior disk displacement (ADD) on type-III, VI and IX collagens of the rabbit craniomandibular joint (CMJ) tissues using an immunohistochemical technique. The right joint was exposed surgically, all discal attachments were severed except for the posterior discal attachment (bilaminar zone). The disk was then repositioned anteriorly and sutured to the zygomatic arch. The left joint served as a sham-operated control. Ten additional joints were used as non-operated controls. Deeply anesthetized rabbits were perfused with 2% buffered formalin 2 weeks (10 rabbits) or 6 weeks (10 rabbits) following surgery. The articular disk, bilaminar zone, mandibular condyle and articular eminence were excised. The last two were decalcified in EDTA. All tissues were then sectioned at 10 microns in a cryostat. Sections were incubated with monoclonal antibodies directed against type-III, VI or IX collagens. Following incubation in the appropriate FITC-labelled secondary antibodies, all sections were studied under the fluorescence microscope. The results showed a reduction in immunostaining for type-VI and IX collagens in the condylar cartilage, disk and articular eminence at 2 weeks, followed by an increase in their immunostaining at 6 weeks and the appearance of a de novo type-III collagen in the condylar cartilage and the articular eminence. It is concluded that surgical induction of ADD in the rabbit CMJ leads to alterations in its type-III, VI and IX collagens.

Tragal cartilage in the primary reconstruction of defects resulting from a nasal septal abscess

Immediate reconstruction of nasal septal sequestration following a septal abscess with autologous tragal cartilage graft is the method of choice in children and adolescents. On one hand autologous tissue is used, thus foreign body reaction with rejection or irregular resorption does not occur. On the other hand further defects in the posterior septal segment with additional damage to growth zones do not arise. Furthermore local tissue is saved, thus it will be available later, in case revision surgery will be necessary. But in contrast to costal cartilage tragal cartilage is easy to obtain in reconstruction of the nasal septum. No visible or functional defect arise at the donor site.

Collagen degradation within subcutaneous air pouches in vivo: the effects of proteinase inhibitors

A straightforward in vivo model of collagen degradation is described that can be used to measure the effects of different classes of proteinase inhibitors. Air pouches, formed subcutaneously in the dorsal thoracic region of rats, were inflamed 6 to 8 days later by injecting lambda-type carrageenan. 14C-Collagen was injected into the air pouches either 1 day before or 1 day after lambda-carrageenan-induced inflammation: in the latter case, the inflammatory exudate fluid was drained from the air pouches immediately prior to administering 14C-collagen. Ninety percent of the 14C-collagen was degraded and cleared within 3 days from pre-inflamed air pouches, but degradation was much slower from the post-inflamed or non-inflamed air pouches. Proteinase inhibitors injected simultaneously with the 14C-collagen, and again 6 hr later, reduced the extent of 14C-collagen degradation from air pouches measured after 24 hr. Forty-two percent of the degradation of 14C-collagen could be inhibited by a mixture of enzyme inhibitors (leupeptin, alpha 1-anti-proteinase, aprotinin, and pepstatin) injected together with 1,10 phenanthroline, the zinc metalloenzyme inhibitor. The 1,10 phenanthroline alone caused a 33% inhibition of 14C-collagen degradation, and the inhibitor mixture given alone inhibited 14C-collagen loss by 25%. Approximately 60% of the degradation of 14C-collagen in this model was mediated by mechanisms resistant to this combination of proteinase inhibitors, which may indicate the significant involvement of non-enzymic modalities, or degradation in intracellular compartments inaccessible to extracellular agents.

Neutrophil gelatinase levels in plasma and synovial fluid of patients with rheumatic diseases

To examine the clinical significance of neutrophil gelatinase in rheumatic diseases, plasma and synovial fluid (SF) gelatinase levels were determined in 62 patients with rheumatoid arthritis (RA), 12 patients with ankylosing spondylitis (AS), 18 patients with osteoarthritis (OA) and 17 healthy controls. The gelatinase level was measured by enzyme-linked immunoassay (ELISA). The assay had a sensitivity of 1 ng/ml and a working range of 5-25 ng/ml. Gelatinase levels were significantly higher in the plasma of patients with RA and of patients with RA complicated by amyloidosis or vasculitis as compared to those of healthy controls. Moreover, the mean value of gelatinase in the plasma of patients with RA complicated by vasculitis was found to be significantly higher than that of RA patients without vasculitis. A significant increase in gelatinase concentration was also observed in the plasma of AS patients but not in the plasma of patients with OA. The concentration of gelatinase in the RA SF samples was much higher (18-fold) than the level of the enzyme in the plasma of RA patients. There was also a higher concentration of gelatinase (four-fold) in OA SF compared with OA plasma. The results suggested that circulating gelatinase may reflect some degree of neutrophil activation in patients with inflammatory arthritis, especially in those with RA complicated by vasculitis. However, the results did not allow a differentiation between chronic and acute inflammation.

Collagenase, gelatinase and elastase activities in sulcular fluid of osseointegrated implants and natural teeth

Proteinases play a key rôle in the physiological degradation and remodelling of the periodontal tissues. The rôle of these enzymes in tissue remodelling remodelling in connection with the insertion of dental endosseous implants has not been elucidated. Therefore, the aim of the present study was to identify the eventual presence of collagenase, gelatinase and elastase activities in periimplant sulcus fluid (PISF) of osseointegrated implants. Gelatinolytic activity in the samples was studied with gelatin-zymograms. Collagenase activity and its susceptibility to tetracycline-inhibition were monitored with SDS-polyacrylamide gel electrophoresis and laser densitometry, and elastase activity with synthetic substrate. Low activities of elastase and collagenase were detected in both PISF of osseointegrated implant patients and gingival crevicular fluid (GCF) of the control patients whereas significantly higher activities were detected in GCF of adult periodontitis patients. Also the profiles of gelatinases were similar in PISF of osseointegrated implant patients and GCF of the controls, but differed from the profile of active gelatinases present in GCF of adult periodontitis patients. The similar activities/characteristics of these proteinases in both periimplant sulcus fluid of healthy dental implants and GCF of healthy natural teeth suggest that they comprise the major proteinases for both periodontal and periimplant tissue remodelling or destruction.

Reduction of collagen degradation in experimental granulation tissue by vitamin E and selenium

The importance of antioxidants in inflammatory tissues has been studied in vivo. Degradation of homologous 3H-collagen powder by experimental granulation tissue induced by cellulose sponges in the rat was monitored as the radioactivity excreted in urine. By administering pharmacological doses of both vitamin E and selenium subcutaneously and by injection into sponges implanted subcutaneously, this breakdown of collagen was reduced. Injections in the sponges also arrested the maturation of the granulation tissue. Vitamin E and selenium are potential inhibitors of the free oxygen radicals from phagocytic inflammatory cells. It is therefore suggested that these radicals may play a rôle in the collagen destruction by granulation tissues, as in periodontitis.

IgG3 reactive rheumatoid factor in rheumatoid arthritis: etiologic and pathogenic considerations

Rheumatoid factor (RF) is a polyclonal autoantibody directed against the Fc portion of IgG. Although the role of RF in patients with rheumatoid arthritis (RA) is unclear, immune complexes that form between RF and IgG can activate the classical complement (C) pathway, leading to pathogenic outcomes involving inflammatory events and tissue damage. The specificity of serum RF and RF produced by rheumatoid synovial cells (RSC) is different. Serum RF has specificity for rabbit IgG and human IgG subclasses IgG1, 2, and 4, but binds poorly to IgG3. The affinity of serum RF for IgG Fc is low, having an association constant of 10(4)-10(5) M-1. RSC RF, however, has specificity for human IgG and high avidity for IgG3. Because of this greater specificity and avidity for IgG3, and because RSC RF may be pathogenically more important than serum RF, an important role for IgG3-reactive RF in RA may exist. Binding of RF to IgG may be dependent on the allotype and glycosylation of IgG. Infectious agents present in RA patients may directly or indirectly induce the production of certain RF. In this communication, we review and expand on several observations examining the role of IgG3-reactive RF in RA including: 1) binding differences between RF derived from RSC and serum; 2) glycosylation characteristics of IgG and its interaction with RF; 3) apparent allotype dependent binding of IgG3-reactive RF; and 4) possible relationship between infectious agents and the production of IgG3-reactive RF. Taken together, these observations suggest an important role for IgG3-reactive RF in better understanding the etiology and pathogenesis of RA.

Localisation of interleukin 8 in the synovial membrane, cartilage-pannus junction and chondrocytes in rheumatoid arthritis

Interleukin-8 (IL-8) may play an important role in the development of synovitis in rheumatoid arthritis (RA), in that it is a powerful chemoattractant for neutrophils and T cells. The aim of this study was to examine the distribution of IL-8 in the synovial membrane and cartilage, from RA, osteoarthritis (OA) and normal joints. By immunohistochemical techniques, IL-8 was shown to be present in the lining layer cells in RA (87%) and in OA (62%). By contrast, only a few of the normal synovial lining layer cells (14%) contained IL-8. Deeper in the membrane the number of IL-8 positive cells decreased. Only vessels were highly positive for IL-8. At the RA cartilage-pannus junction 26% of the cells contained IL-8, whereas at the OA cartilage-pannus junction 8% of the cells were IL-8 positive (P < 0.05). Chondrocytes present in joint surface cartilage stained positive for IL-8 in an average of 20% of the cells of both RA and OA. These results provide histological evidence that IL-8 is present in the arthritic synovial tissue and cartilage, and is distributed in a manner that may form a chemotactic gradient, which favours localisation of neutrophils to the joint lumen.

Proteolytic inactivation of alpha 1-antitrypsin and alpha 1-antichymotrypsin by neutrophils in arthritic joints

OBJECTIVE

In vitro, activated neutrophils create a microenvironment in which proteinase inhibitors are inactivated through the coordinate action of reactive oxygen species and released elastase. We investigated whether such a mechanism may contribute to the destruction of the joint tissues in arthritis.

METHODS

We analyzed the state of alpha 1-antitrypsin (alpha 1AT) and alpha 1-antichymotrypsin (alpha 1ACT), the two major inhibitors of the neutrophilic serine proteinases, in synovial fluid (SF) from patients with inflammatory arthropathies (n = 71) and osteoarthritis (OA) (n = 11), and related the results to neutrophil activation in SF.

RESULTS

The ratio of functional to antigenic levels of alpha 1AT in SF of patients with inflammatory joint diseases was similar to that of alpha 1AT in normal plasma, whereas that of alpha 1ACT was significantly decreased. Patients with inflammatory arthropathies had significantly higher levels of inactivated alpha 1AT (i alpha 1AT) and inactivated alpha 1ACT (i alpha 1ACT) in SF (as determined with monoclonal antibodies specific for the inactivated [i.e., proteolytically inactivated and/or complexed] forms of these inhibitors) than patients with OA (P < 0.005). Inactivated alpha 1AT and i alpha 1ACT levels corresponded to 0.3-11% and 3-99%, respectively, of the total amount of these inhibitors in SF. Most of the i alpha 1AT in SF had a lower M(r) than that of native alpha 1AT. Inactivated alpha 1ACT in SF had an M(r) identical to that of nonfunctional alpha 1ACT in plasma treated with chymotrypsin. Levels of both i alpha 1AT and i alpha 1ACT correlated significantly with lactoferrin and elastase levels.

CONCLUSION

These results suggest that alpha 1AT and alpha 1ACT in arthritic joints are inactivated in part by activated neutrophils, suggesting a role for these cells in impairment of the local balance between proteinases and their inhibitors in arthritis.

Inhibitory effects of hyaluronan on neutrophil-mediated cartilage degradation

The effects of hyaluronan on neutrophil-mediated cartilage degradation were studied in an in vitro model. Rat peritoneal neutrophils were incubated for up to 18 h with the neutralized cartilage of bovine nasal septa using N-formyl-L-methionyl-L-leucyl-L-phenylalanine combined with cytochalasin B, or opsonized zymosan, as a stimulation agent of neutrophils. Hyaluronan inhibited the neutrophil-mediated cartilage degradation by reducing the release of sulfated glycosaminoglycans from the cartilage. Inhibitory effects were dependent on concentration and molecular weight of hyaluronan. These results suggest that hyaluronan with a high molecular weight plays an important role in protecting the articular cartilage in inflamed joints from neutrophil injury.

Oxidation resistant muteins of antileukoproteinase as potential therapeutic agents

Native antileukoproteinase (ALP) and two oxidant resistant mutants ALP 242 and ALP 231 were synthesized by means of recombinant DNA technology. In the ALP 242 molecule the methionine residue located in the reactive centre of the binding loop is replaced by a leucine residue. In ALP 231 all four methionine residues of the second domain were substituted by leucine residues. The native inhibitor and the two oxidant resistant molecules show comparable inhibitory capacities towards human neutrophil elastase (HLE) and cathepsin G. All three inhibitors were treated with different reactive oxygen species. After incubation with chloramine T or supernatants of activated polymorphonuclear leukocytes (PMN's) a drastic drop of inhibitory capacity of the native molecule was observed. Compared to the native form of ALP the mutant ALP 242 was less inactivated, whereas ALP 231 was nearly totally resistant towards all reactive oxygen. (Heinzel-Wieland R. et al., Biomed Biochim Acta 50: 677-681 (1991)) The intratracheal administration of HLE into the lung of Syrian Hamsters induced mild to moderate emphysematous lesions. The inhibitory potencies of native ALP and the ALP mutants were determined in this animal model by means of intratracheal instillation of the different molecules one hour prior to the administration of HLE. The inhibitory effects of ALP 242 and ALP 231 towards HLE-induced emphysema were significantly better than that of the native molecule. Surprisingly no significant differences between the two mutants were observed. (Rudolphus A. et al., Clin Sci 81: 777-784 (1991)) In a second animal model the emphysema was induced by repeated intratracheal administration of lipopolysaccharides (LPS) into the hamster lungs. This model is characterized by a chronic process of inflammation probably caused by a continuous release of endogenous elastase from infiltrating PMN's. Repeated applications of 1 mg of ALP 242 reduced the LPS-induced emphysema by 70 to 80%. In contrast, equal amounts of the native molecule resulted in significantly lower inhibition of the LPS-induced emphysema, only 23-30% reduction was observed. Repeated applications of 1 mg of ALP 231 reduced the LPS-induced emphysema only about 50%. So far it is not yet clear, why the totally oxidant resistant ALP 231 was less effective than the ALP 242 molecule. (Stolk J. et al., Pulmonary Pharmacology in press (1992))

Synthesis of 35S-labelled macromolecules by polymorphonuclear neutrophils. Evidence for the production of [35S]sulphite which can modify both endogenous and exogenous proteins

The incorporation of [35S]sulphate into macromolecules by rabbit peritoneal polymorphonuclear neutrophils (PMN) in vitro revealed that two major groups of 35S-labelled macromolecules were synthesized by these cells. The first group did not bind to anion-exchange columns at pH 6.0 and contained 60-80% of the total incorporated radiolabel. The second group did bind to anion-exchange columns at pH 6.0 and eluted as a single peak of radioactivity at an ionic strength characteristic of sulphated proteoglycans; it accounted for the remaining incorporated radiolabel. Analysis of this material on Sepharose CL-6B demonstrated that 35S-labelled macromolecules isolated from the cell extract migrated with Kav. of 0.36, while corresponding material isolated from the medium migrated with Kav. of 0.51. When subjected to electrophoresis on SDS/polyacrylamide gels the intact proteoglycan had a molecular mass of approx. 90 kDa and yielded two core proteins of molecular mass 31 kDa and 28 kDa after digestion with chondroitinase ABC. The peak of labelled macromolecules which did not bind to the anion-exchange column was found, by SDS/PAGE, to comprise 35S-labelled proteins of various molecular masses. The 35S label was displaced from this fraction by treatment with 0.1 M-sodium sulphite, suggesting that the radiolabel was in the form of an S-sulpho sulphite derivative. Using the sulphite-trapping agents N-2,4-dinitroanilinomaleimide and cyst(e)ine, [35S]sulphite was detected in the incubation medium of PMN, indicating that these cells were able to synthesize [35S]sulphite from [35S]sulphate. The release of [35S]sulphite from neutrophil cultures was calculated to be 78 pmol/h per 10(6) cells. When exogenous proteins were included in the incubation medium of cell cultures, the [35S]sulphite reacted with these proteins to form a stable 35S-labelled conjugate.

Damage of cultured chondrocytes by hydrogen peroxide derived from polymorphonuclear leukocytes: a possible mechanism of cartilage degradation

To study the mechanisms of chondrocyte damage, chondrocyte cytotoxicity as shown by chromium-51 release induced by polymorphonuclear leukocytes (PMNLs) was examined. PMNLs significantly enhanced chondrocyte cytotoxicity in the presence of phorbol dibutyrate. This chondrocyte damage was abolished by the addition of catalase, whereas superoxide dismutase and scavengers of hydroxyl radicals and protease inhibitors failed to reverse it. When cartilage matrix components such as hyaluronic acid and various proteoglycans were added to the PMNL-chondrocyte cultures, these components failed to affect the chromium-51 release. These results suggest that the increase in chondrocyte cytotoxicity is due to hydrogen peroxide generated by the PMNLs, and that cartilage matrix components do not prevent it. Hydrogen peroxide from PMNLs may therefore play an important role in cartilage degradation through direct damage of chondrocytes during inflammatory process.

Analysis of intraarticular fibrinolytic pathways in patients with inflammatory and noninflammatory joint diseases

OBJECTIVE

Intraarticular activation of the fibrinolytic system has been suspected to occur in patients with arthritis. We undertook the present study to investigate the relation of this activation to clinical symptoms, and the molecular pathways involved.

METHODS

We quantitatively assessed levels of plasmin-alpha 2-antiplasmin (PAP) complexes in synovial fluid (SF) from 25 patients with rheumatoid arthritis (RA), 7 with seronegative spondylarthropathy (SSA), and 10 with osteoarthritis (OA), and conducted an analysis to determine the plasminogen-activating pathway via which these complexes were generated. In addition, we studied the relationship of intraarticular fibrinolysis to clinical and biochemical parameters.

RESULTS

All patients studied had increased SF levels of PAP complexes. Levels in patients with RA and SSA were slightly higher than those in patients with OA. These complexes were probably formed by activation of urokinase-type plasminogen activator (u-PA), and not tissue-type plasminogen activator (t-PA), since SF levels of both u-PA antigen and u-PA-plasminogen activator inhibitor (PAI) complexes were increased in 27 of the 42 patients. Conversely, SF levels of t-PA were below normal in all but 1 patient. In some patients, activation of factor XII presumably also contributed to plasminogen activation in SF, since levels of factor XIIa-C1 inhibitor in SF were increased in 8 of the 42 patients and correlated, as did u-PA-PAI levels, with levels of PAP complexes. Several of the parameters of fibrinolysis in SF, particularly u-PA antigen and u-PA-PAI-1 complexes, were found to correlate with clinical and biochemical parameters.

CONCLUSION

Our results suggest that plasminogen is frequently activated in the joints of patients with inflammatory or noninflammatory arthropathy and that this activation mainly occurs via a u-PA-, and in some cases also via a factor XII-, dependent pathway. The possible relation of this activation process to stimulation of synovial cells by cytokines is discussed.

The serine-protease inhibitor of cartilage matrix is not a chondrocytic gene product

Human articular cartilage contains significant amounts of antileukoprotease, a cationic low-molecular-mass serine-protease inhibitor, which was originally purified from mucous secretions (synonym: secretory leukocyte proteinase inhibitor). As it was not known whether the inhibitor molecule is also synthesized locally, we investigated antileukoprotease gene expression in chondrocytes. No antileukoprotease-specific mRNA was detected in adult or foetal human chondrocytes by in situ hybridization, Northern-blot analysis or polymerase chain reaction. Concurrently, the chondrocytes remained unstained on immunohistology, whereas immunoreactive antileukoprotease was demonstrated in the cartilage matrix. By Northern-blot analysis, the antileukoprotease message was detected in the promyelocytic cell line HL60, the myelomonocytic cell line U937 and even in mature polymorphonuclear leukocytes from the peripheral blood of healthy donors. Immunoperoxidase staining of polymorphonuclear leukocytes for the antileukoprotease protein indicated that this cell is likely to be the physiological source of the inhibitor in serum. The results further suggest an accumulation of the inhibitor in the cartilage matrix.

The effects of selective matrix degradation on the short-term compressive properties of adult human articular cartilage

The effects of proteoglycan and collagen digestion on the transient response of human articular cartilage when tested in unconfined compression were determined. Small cylindrical specimens of cartilage, isolated from the femoral head of the hip joint and from the femoral condyles of the knee joint, were subjected to a suddenly applied compressive load using a test apparatus designed to yield a transient oscillatory response. From this response values of the elastic stiffness and the viscous damping coefficient were determined. Cathepsin D and cathepsin B1 were used to digest the proteoglycan in some specimens, while in other specimens leukocyte elastase was used to attack the non-helical terminal regions of the Type II tropocollagen molecules and possibly the Type IX collagen molecule and thereby disturb the integrity of the collagen mesh. The results showed that proteoglycan digestion alone reduced the viscous damping coefficient but it did not significantly alter the elastic stiffness as determined from the oscillatory response. In contrast, the action of elastase reduced both the damping coefficient and the elastic stiffness of the cartilage. The results demonstrated the role of proteoglycans in regulating fluid transport in cartilage and hence controlling the time-dependent viscous properties. The elastic stiffness was shown to be dependent on the integrity of the collagen fibre network and not on the proteoglycans.

Michaelis complexes of porcine pancreatic elastase with 7-[(alkylcarbamoyl)amino]-4-chloro-3-ethoxyisocoumarins: translational sampling of inhibitor position and kinetic measurements

A step leading to the formation of the covalent complexes between porcine pancreatic elastase (PPE) and 7-[(alkylcarbamoyl)amino]-4-chloro-3-ethoxyisocoumarins (alkylHNCO-EICs) is the formation of the noncovalent Michaelis complex. No average structures are available for the Michaelis complexes of PPE with alkylHNCO-EICs. We present the results of an initial step in obtaining these structures and have determined kinetic constants as well. The kinetic results indicate that formation of the Michaelis complex is what differentiates the effectiveness of these inhibitors in inactivating PPE. The structural and kinetic results together suggest that the structure of the Michaelis complex is necessary for the design of potent alkylHNCO-EIC inhibitors of PPE. Two novel alkylHNCO-EICs are predicted to be the best inhibitors of this series. An alternate mechanism for serine protease inhibition is also proposed. Evidence for, and studies that may add support to, the hypothesized mechanism are discussed.

Arthritis induced immunologically with cationic amidated bovine serum albumin in the guinea pig. A morphological and biochemical study on the destruction of articular cartilage

Arthritis was induced by injecting cationic amidated bovine serum albumin (aBSA) (pI approximately 9.2) into the knee joint of immunized guinea pigs and the mechanisms of articular cartilage destruction were studied morphologically and biochemically. Marked synovitis associated with polymorphonuclear leukocyte (PML) infiltration occurred within 1 day of the challenge. Articular cartilage infiltrated by PMLs was almost completely destroyed after 2 weeks. During the initial destructive process, proteoglycans were depleted from the cartilage and later collagen fibers disappeared. Granulation tissue growing in the inflamed synovium and bone marrow replaced the destroyed cartilage and joint cavity and formed fibrous scar tissue (fibrous ankylosis) by 8 weeks. Subsequently, the knee joints developed cartilagenous ankylosis by 12 weeks and finally bony ankylosis at 28 weeks. Autoradiography using 125I-aBSA and immunofluorescence studies for immunoglobulin (IgG) and complement (C3) demonstrated that the antigen is trapped in all zones of the articular cartilage and serves as a trigger for immune complex formation. Significantly increased neutral proteinase activities against substrates of proteoglycan subunits, [3H]carboxymethylated transferrin and L-pyroglutamyl-L-prolyl-L-valine-paranitroanilide were detected in homogenates of the synovium and cartilage from arthritic knee joints 1 and 2 weeks after induction. Inhibitor studies and pH curves suggested that the proteinase is leukocyte elastase. Measurable amounts of gelatinolytic activity, detected by activation with 4-aminophenylmercuric acetate and inhibited with EDTA, were also present in the same samples, but there was no detectable collagenase activity. The data on SDS-gelatin substrate gel showed that the proteinase is gelatinase derived from PMLs. These results suggest that in aBSA-induced arthritis, elastase and gelatinase from PMLs invading articular cartilage may play important roles in cartilage destruction.

Predominant role of neutrophils in the inactivation of alpha 2-macroglobulin in arthritic joints

We studied the state of alpha 2-macroglobulin (alpha 2M), an important inhibitor of cartilage-degrading proteinases, in relation to activation of neutrophils in 82 patients with several types of arthritis, including 52 with rheumatoid arthritis and 11 with osteoarthritis. Levels of total inactive alpha 2M (i alpha 2M), which comprises alpha 2M complexed to proteinases and alpha 2M inactivated by oxidation or hydrolysis, were measured with a monoclonal antibody specific for i alpha 2M. In addition, levels of alpha 2M complexed to proteinases were quantitated with specific assays. Neutrophil activation was assessed by measuring elastase-alpha 1-antitrypsin complexes and lactoferrin. In 83% of the 82 patients tested, the synovial fluid (SF) to plasma ratio of i alpha 2M exceeded 1, indicating an intraarticular generation. Levels of i alpha 2M significantly correlated with neutrophil numbers (P less than 0.0005) and with levels of elastase-alpha 1-antitrypsin complexes and of lactoferrin (P less than 0.00001 for both). Moreover, part of i alpha 2M consisted of alpha 2M complexed to elastase-like and chymotrypsin-like proteinases, presumably, neutrophil elastase and cathepsin G, respectively. However, the amount of i alpha 2M was approximately 10-fold larger than the amount complexed to these proteinases. In vitro inactivation of alpha 2M by activated neutrophils was only partly inhibitable by eglin C, a specific inhibitor of both elastase and cathepsin G. Release of reactive oxygen species was presumably responsible for the additional inactivation of alpha 2M, because eglin C completely abolished the inactivation of alpha 2M by cell-free supernatant of activated neutrophils. Thus, our results suggest a predominant role of neutrophils in the inactivation of alpha 2M in the SF of patients with inflammatory joint diseases. However, this inactivation could be explained only in part by the release of neutrophilic proteinases. We propose that the inactivation of alpha 2M in SF was due to the concerted action of both reactive oxygen species and lysosomal proteinases.

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.

Purification of a serine-proteinase inhibitor from human articular cartilage. Identity with the acid-stable proteinase inhibitor of mucous secretions

An inhibitor of the serine proteinases human leucocyte elastase (EC 3.4.21.37), of cathepsin G (EC 3.4.21.20) and of trypsin (EC 3.4.21.4) has been purified from human articular cartilage. The apparent Mr of the cationic (pI greater than 10) protein was determined to 15,000 by SDS/PAGE. It was shown to cross-react in Western blot with a specific antibody to a recombinant-derived serine-proteinase inhibitor of human mucous secretions. Identity of both inhibitors is indicated by the determination of the N-terminal amino acid sequence of the cartilage-derived serine-proteinase inhibitor. In all 24 residues the cartilage inhibitor was shown to be identical with the human secretory leucocyte proteinase inhibitor ('SLPI'). The inhibitor molecule may play a crucial role in the protection of cartilage matrix proteins against proteolytic attack.

The role of proteinases in cartilage destruction

Most of the organic, extracellular matrix of articular cartilage consists of collagens and proteoglycans. Their degradation is initiated extra- or peri-cellularly by proteinases produced locally by cells in and around the joint. Although enzymes from all four classes of proteinases can degrade the cartilagenous matrix, serine proteinases, particularly plasmin, and various neutral metalloproteinases (NMPs) are likely to be the key enzymes in this process. Much attention has been paid to members of the latter group, which are synthesised both by the resident, mesenchymal cells of the joint and by various types of white blood cells which colonise it during inflammation. NMPs can be conveniently grouped into three classes, the collagenases, the stromelysins and the gelatinases. Two members are known for each class, with the recently identified "pump" (Putative Metalloproteinase) probably constituting a third member of the stromelysin group. Regulation of these enzymes is complex. Cells normally synthesise NMPs at low rates, but their production increases markedly following cellular activation by cytokines or certain other stimuli. Major control points for enzyme synthesis occur at the levels of transcription and the conversion of proenzyme to active enzyme; enzyme activity is further regulated through the action of inhibitors. Alpha-2 macroglobulin is the major systemic inhibitor, while a number of tissue inhibitors act as local regulators. These include at least two TIMPs and several IMPs. Pharmacologic manipulation of NMP activity holds promise as an approach to anti-erosive therapy in arthritis.

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.

Effects of dietary supplementation with eicosapentaenoic acid or gamma-linolenic acid on neutrophil phospholipid fatty acid composition and activation responses

Previous data that alimentation with fish oil rich in eicosapentaenoic acid (EPA; 20:n-3) or vegetable oil rich in gamma-linolenic acid (GLA; 18:3n-6) can reduce symptoms of inflammatory skin disorders lead us to determine the effects of dietary supplements of oils rich in EPA or GLA on guinea pig (GP) neutrophil (PMN) membrane potential (delta gamma), secretion, and superoxide (O2-) responses. Weanling GPs were initially fed diets supplemented with olive oil (less than 0.1% EPA; less than 0.1% GLA) for 2 weeks, followed by a crossover by two sets of animals to diets supplemented with fish oil (19% EPA) or borage oil (25% GLA). At 4-week intervals, 12% sterile casein-elicited peritoneal neutrophils (PMN) were assessed for membrane polyunsaturated fatty acid (PUFA) profiles and FMLP-, LTB4-, and PMA-stimulated delta gamma changes, changes in flow cytometrically measured forward scatter (FWD-SC) (shape change), 90 degrees scatter (90 degrees -SC) in cytochalasin B-pretreated-PMN (secretion response), and superoxide responses, GP incorporated EPA and GLA (as the elongation product, dihomo-GLA or DGLA) into their PMN phospholipids by 4 weeks. The peritoneal PMN of all groups demonstrated broad resting FWD-SC and poor activation-related FWD-SC increases, suggesting in vivo activation. While secretion was comparable in the three groups in response to FMLP, there was a trend toward inhibition of LTB4-stimulated 90 degrees -SC loss in both fish and borage oil groups. This was significant only with borage oil (21.7 +/- 2.1 vs 15.3 +/- 1.2% loss of baseline 90 degrees -SC, olive vs borage: P = 0.03). PMN from borage- and fish oil-fed GPs showed a progressively lower O2- response to FMLP than the olive oil group (73.9 +/- 3.9 and 42.9 +/- 6.8% of olive oil response for borage and fish oils, respectively; P less than 0.005 and P less than 0.01, respectively, at 12 weeks), while PMA-stimulated O2- was inhibited only in the fish oil-fed group and only at 12 weeks (62.0 +/- 2.7% of control; P less than 0.025). We conclude that dietary supplementation with oils rich in PUFAs can modify PMN activation responses.

Plasma and synovial fluid levels of granulocytal elastase-alpha-1-protease inhibitor complex in patients with rheumatoid arthritis

Plasma and synovial fluid levels and granulocytal elastase-alpha-1-protease inhibitor complex (EIC) in patients with rheumatoid arthritis (RA) were measured by enzyme-linked immunoassay and the results compared with those in patients with osteoarthrosis (OA). It was found that the plasma and synovial fluid levels of EIC in RA patients were higher than those in OA patients. There was a positive correlation between plasma EIC level in RA patients in Lansbury's index score of disease activity, as this tends to be higher when titer of RAHA in the plasma is high. The level of EIC in the synovial fluids correlated positively with granulocyte count and alpha-1-protease inhibitor (alpha-1-PI) level, and this, too, tends to be higher when titer of RAHA in synovial fluid is high. The results suggested that the level of EIC in the plasma or synovial fluids can be a good marker for the systemic or localized activation of the granulocytes and that IgM rheumatoid factor (IgMRF) is involved in the mechanism of the release of elastase.

The kinetic mechanism of inhibition of human leukocyte elastase by MR889, a new cyclic thiolic compound

The cyclic thiolic compound 2-[3-thiophencarboxythio]-N-[dihydro-2(3H)-thiophenone-3-il] - propionamide (MR889) was investigated as inhibitor of endopeptidases. The activity of bovine pancreatic alpha-chymotrypsin, human leukocyte cathepsin G and rabbit liver cathepsin B was not affected by MR889, whereas porcine pancreatic elastase and human leukocyte elastase were inhibited. The kinetic mechanism of inhibition of human leukocyte elastase was of the reversible, slow-binding, fully competitive type. The rate constants for complex formation between MR889 and leukocyte elastase, determined by pre-steady-state kinetic analysis in the presence of a tetrapeptide substrate at 37 degrees and pH 7.40, were kon = 2363 +/- 15 M-1 sec-1, koff = 3.01 +/- 0.34 x 10(-3) sec-1. The inhibition equilibrium constant was Ki = koff/kon = 1.27 +/- 0.15 microM. Ki, calculated from steady-state kinetic experiments, was 1.38 microM. MR889 also inhibited the elastolytic activity of leukocyte elastase, as determined with insoluble elastin as the substrate.

Synovial fluids from infected joints contain metalloproteinase--tissue inhibitor of metalloproteinase (TIMP) complexes

Samples of synovial fluids aspirated from patients with septic arthritis prior to the commencement of any treatment contained active metalloproteinases but no proteinase inhibitory activity. We therefore assayed these samples for proteinase-inhibitor complexes. Although no biologically active alpha 2-macroglobulin or tissue inhibitor of metalloproteinase (TIMP) was present in the fluids, immunoassay of the samples clearly showed that high molecular weight proteinase-TIMP complexes were present. It is proposed that high levels of active metalloproteinases are released from neutrophils into septic synovial fluids and that these proteinases complex all the available TIMP, forming metalloproteinase-TIMP complexes.

Production and purification of prostromelysin and procollagenase from IL-1 beta-stimulated human gingival fibroblasts

Conditions were established to stimulate human gingival fibroblast explant cultures to synthesize milligram quantities of the metalloproteinase proenzymes, prostromelysin and procollagenase. To stimulate enzyme production, cells were treated with 1 nM recombinant human IL-1 beta for approximately 7 days under serum free conditions. Using a combination of rapid column chromatography steps, approximately 10 milligrams of prostromelysin and 5 milligrams of procollagenase were purified from 1 liter of conditioned media. Prostromelysin electrophoresed as a doublet with molecular weights of 55,57 kD, whereas, procollagenase migrated with slightly lower molecular weights of 52, 54 kD. Both proenzymes were treated with trypsin or aminophenylmercuric acetate to generate active species. The molecular weights of the active enzymes were approximately 10 kD smaller than the proenzymes. Active enzymes were inhibited by metal chelators and the natural metalloproteinase inhibitor, tissue inhibitor of metalloproteinase (TIMP), but not by the serine protease inhibitor, phenylmethylsulfonyl fluoride (PMSF). Activated stromelysin degraded a number of substrates including transferrin, proteoglycan monomer, proteoglycan aggregated with hyaluronic acid, and substance P. By contrast, collagenase degraded interstitial type I collagen and the peptide thioester, Ac-Pro-Leu-Gly-SCH(iBu)Co-Leu-GlyOEt. Identity of both enzymes were confirmed by amino-terminal protein sequence analysis as well as by immunoblot analysis using monoclonal antibodies.

Mechanisms of human neutrophil-mediated cartilage damage in vitro: the role of lysosomal enzymes, hydrogen peroxide and hypochlorous acid

Cartilage is a focal point of attack by cellular and molecular elements of the inflammatory response which occurs in arthritic diseases. Neutrophils damage articular cartilage by degrading matrix components and inhibiting their synthesis. The aim of this study was to elucidate mechanisms of this damage. Human neutrophils were isolated from blood by centrifuging through Ficoll-Hypaque and granule extract prepared from them. Articular cartilage from adult humans and cattle was maintained in organ culture. Cartilage degradation (release of 35S-labelled proteoglycan) or synthesis (incorporation of 35S into proteoglycan) was determined after various treatments. Human neutrophils and neutrophil granule extract degraded proteoglycan and inhibited proteoglycan synthesis. The specific leucocyte elastase inhibitor N-methoxysuccinyl-(ala)2-pro-val-chloromethylketone (MAAPVCMK) partially reversed these effects. H2O2, a product of the neutrophil respiratory burst, when added directly at 10(-6)mol/L, or generated by glucose oxidase (GO)/glucose inhibited proteoglycan synthesis but had no effect on degradation. Hypochlorous acid (OHCl), a product of the myeloperoxidase (MPO)/H2O2/Cl system at 50 mumol/L degraded proteoglycan and inhibited its synthesis. OHCl produced by granule extract (as a source of MPO) + GO-generated H2O2 + Cl- degraded proteoglycan. The results indicate that neutrophil-mediated proteoglycan degradation and inhibition of synthesis is largely attributable to elastase and secondarily to OHCl, whereas H2O2 impairs synthesis without affecting degradation of proteoglycan.

Immunolocalization of matrix metalloproteinase 3 (stromelysin) in rheumatoid synovioblasts (B cells): correlation with rheumatoid arthritis

Metalloproteinases produced by connective tissue cells may play a key part in the destruction of joints in rheumatoid arthritis. Matrix metalloproteinase 3 (MMP-3; stromelysin) capable of degrading cartilage proteoglycans and type IX collagen and of activating procollagenase was immunolocalised in hyperplastic synovial lining cells in rheumatoid synovium, but not in the cells of normal synovium. Cells responsible for synthesis of MMP-3 have the phenotype of synovioblasts (B cells) by immunoelectron microscopy, but not of phagocytic synovial macrophages (A cells). Cultured monolayer of rheumatoid synovial cells synthesises MMP-3 only under treatment with macrophage conditioned medium. Immunolocalisation of MMP-3 in rheumatoid synovium and cultured synovial cells was possible when the specimens were treated with a monovalent ionophore, monensin. These results suggest that MMP-3 is synthesised and secreted continuously without storage from hyperplastic synovioblasts stimulated by factor(s) derived from activated macrophages present in the synovium.

Chondrocyte activation by a putative interleukin-1 derived from lapine polymorphonuclear leukocytes

Polymorphonuclear leukocytes (PMNs) recovered from 4-h lapine peritoneal exudates contained factors which provoked the synthesis of collagenase, gelatinase, caseinase, and prostaglandin E2 by lapine articular chondrocytes. Rapid secretion of these factors occurred after exposing the polymorphs to phorbol myristate acetate or formyl-Met-Leu-Phe. Fractionation of polymorph lysates by HPLC size exclusion chromatography provided a molecular weight of approximately 14,000 for the active principle. Examination of the most active fraction by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, followed by silver staining, confirmed the presence of a single band with this apparent molecular weight. Isoelectric focusing of this fraction revealed the presence of four distinct bands with the pI values 6.90, 7.05, 7.45, and 7.55. This fraction tested positive in a bioassay for interleukin-1. We were unable to activate chondrocytes by exposure to extracts of human PMNs from either peripheral blood or inflammatory synovial fluid.

Semisynthesis of Arg15, Glu15, Met15, and Nle15-aprotinin involving enzymatic peptide bond resynthesis

The semisynthesis of homologues of aprotinin, the bovine pancreatic trypsin inhibitor, is described. The P1 lysine15 residue was replaced by two methods. The first procedure, which consisted of two enzymatic steps for the incorporation of other amino acids has previously been described. The second approach consisted of six steps of both enzymatic and chemical nature. The modified inhibitor, in which the lysine15-alanine16 peptide bond is hydrolyzed, was used as the starting material. All carboxyl groups of the modified inhibitor were esterified with methanol; the lysine15 methylester group was then selectively hydrolyzed. Afterward, lysine15 itself was split off. Arginine, glutamic acid, methionine, and L-2-aminohexanoic acid (norleucine, Nle) were incorporated using water-soluble carbodiimide combined with an acylation catalyst. The methylester group was used to prevent polymerization. The reactive-site peptide bonds were resynthesized using either chymotrypsin or trypsin.