Cartilage proteoglycan depletion in acute and chronic antigen-induced arthritis

Enzyme targeted delivery of sivelestat loaded nanomicelle inhibits arthritic severity in experimental arthritis

AIMS

Rheumatoid arthritis (RA) is chronic inflammatory disorder mainly affects the lining of articular cartilage of synovial joints characterized by severe inflammation and joint damage. The expression of proteolytic enzymes like MMP-2 and Neutrophil Elastase (NE) worsens the RA condition. To address this concern, we have synthesized dual enzyme targeted chlorotoxin conjugated nanomicelles loaded with sivelestat as broad spectrum treatment for RA.

MATERIALS AND METHODS

Conjugation of the chlorotoxin over nanomicelle and incorporation of sivelestat in nanomicelle provide it dual targeting potential. The sivelestat loaded nanomicelle (SLM) evaluated for the drug release and in-vitro cytocompatibility. Further, investigated its in-vivo anti-arthritic potential on collagen-induced arthritis in wistar rats.

KEY FINDINGS

The microscopic observation of SLM showed spherical ball like appearance with size ranging from 190 to 230 nm. SLM showed good drug loading and encapsulation efficiency along with no cytotoxicity against healthy cell lines. In-vivo therapeutic assessment on collagen induced arthritis rat model showed potential chondroprotection. The microscopic visualization of articular cartilage by staining showed that it restores the cartilage integrity and lowers the expression of pro-inflammatory enzymes showed by Immunohistochemistry and Immunofluorescence. We observed that, it restrain the mediators of synovial inflammation by simultaneous inhibition of the proteolytic enzymes involved in swelling, cartilage destruction and joint damage which provides strong chondroprotection.

SIGNIFICANCE

We report that significant alleviation of inflammation and inhibition of proteolytic enzymes together might provide enhanced potential for the treatment and management of RA.

Caffeic Acid Modified Nanomicelles Inhibit Articular Cartilage Deterioration and Reduce Disease Severity in Experimental Inflammatory Arthritis

Inflammation plays an important role in the development of rheumatoid arthritis (RA). NR4A1 is an anti-inflammatory orphan nuclear receptor involved in protection from inflammatory stimuli in RA. In this study we have explored the anti-inflammatory potential of the FDA-approved drug 9-aminoacridine (9AA) and the natural compound caffeic acid (CA) conjugated to nanomicelles for the treatment of RA. We have synthesized methoxy polyethylene glycol polycaprolactone block copolymer (mPEG-b-PCL) by ring opening polymerization of ε-caprolactone. Then, we conjugated the hydrophilic caffeic acid (CA) with mPEG-b-PCL micelles via Steglich esterification and incorporated the 9AA drug. These nanomicelles were formulated by the solvent evaporation method with a size distribution around 190 nm and showed maximum drug loading capacity along with sustained drug release behavior. Furthermore, we tested the therapeutic potential of the formulated 9AA-encapsulated CA-conjugated nanomicelles (9AA-NMs) against an experimental RA model. We observed promising results which showed alleviation of arthritic symptoms by reducing inflammation, joint damage, bone erosion, and swelling. Further, collagen destruction was significantly reduced in articular cartilage, as shown by safranin-O and toluidine blue staining. The protective mechanism might be due to the simultaneous inhibition of NF-κB by 9AA and CA, whereas the activation of NR4A1 by 9AA leads to the suppression of HIF-1α. This combined therapeutic effect of 9AA and CA has enhanced the therapeutic efficacy of 9AA-NM and markedly reduced the severity of inflammatory arthritis. Unlike existing drugs for pain management and with limited efficacy, 9AA-NM exerted a disease-relevant activation/blockade that alleviated inflammation and exhibited marked therapeutic efficacy against RA.

An Ion-exchange Bone Demineralization Method for Improved Time, Expense, and Tissue Preservation

Here, we describe an ethylenediaminetetraacetic acid (EDTA)-based bone demineralization procedure that uses cation-exchange resin and dialysis tubing. This method does not require solution changes or special equipment, is faster than EDTA alone, is cost-effective, and is environmentally friendly. Like other EDTA-based methods, this procedure yields superior tissue preservation than formic acid demineralization. Greater protein antigenicity using EDTA as opposed to formic acid has been described, but we also find significant improvements in carbohydrate-based histological staining. Histological staining using this method reveals cartilage layers that are not distinguishable with formic acid demineralization. Carbohydrate preservation is relevant to many applications of bone demineralization, including the assessment of osteoarthritis from bone biopsies and the use of demineralized bone powder for tissue culture and surgical implants. The improvements in time, expense, and tissue quality indicate this method is a practical and often superior alternative to formic acid demineralization.

Anisotropic properties of articular cartilage in an accelerated in vitro wear test

Many material properties of articular cartilage are anisotropic, particularly in the superficial zone where collagen fibers have a preferential direction. However, the anisotropy of cartilage wear had not been previously investigated. The objective of this study was to evaluate the anisotropy of cartilage material behavior in an in vitro wear test. The wear and coefficient of friction of bovine condylar cartilage were measured with loading in directions parallel (longitudinal) and orthogonal (transverse) to the collagen fiber orientation at the articular surface. An accelerated cartilage wear test was performed against a T316 stainless-steel plate in a solution of phosphate buffered saline with protease inhibitors. A constant load of 160 N was maintained for 14000 cycles of reciprocal sliding motion at 4 mm/s velocity and a travel distance of 18 mm in each direction. The contact pressure during the wear test was approximately 2 MPa, which is in the range of that reported in the human knee and hip joint. Wear was measured by biochemically quantifying the glycosaminoglycans (GAGs) and collagen that was released from the tissue during the wear test. Collagen damage was evaluated with collagen hybridizing peptide (CHP), while visualization of the tissue composition after the wear test was provided with histologic analysis. Results demonstrated that wear in the transverse direction released about twice as many GAGs than in the longitudinal direction, but that no significant differences were seen in the amount of collagen released from the specimens. Specimens worn in the transverse direction had a higher intensity of CHP stain than those worn in the longitudinal direction, suggesting more collagen damage from wear in the transverse direction. No anisotropy in friction was detected at any point in the wear test. Histologic and CHP images demonstrate that the GAG loss and collagen damage extended through much of the depth of the cartilage tissue, particularly for wear in the transverse direction. These results highlight distinct differences between cartilage wear and the wear of traditional engineering materials, and suggest that further study on cartilage wear is warranted. A potential clinical implication of these results is that orienting osteochondral grafts such that the direction of wear is aligned with the primary fiber direction at the articular surface may optimize the life of the graft.

Rodent preclinical models for developing novel antiarthritic molecules: comparative biology and preferred methods for evaluating efficacy

Rodent models of immune-mediated arthritis (RMIA) are the conventional approach to evaluating mechanisms of inflammatory joint disease and the comparative efficacy of antiarthritic agents. Rat adjuvant-induced (AIA), collagen-induced (CIA), and streptococcal cell wall-induced (SCW) arthritides are preferred models of the joint pathology that occurs in human rheumatoid arthritis (RA). Lesions of AIA are most severe and consistent; structural and immunological changes of CIA best resemble RA. Lesion extent and severity in RMIA depends on experimental methodology (inciting agent, adjuvant, etc.) and individual physiologic parameters (age, genetics, hormonal status, etc.). The effectiveness of antiarthritic molecules varies with the agent, therapeutic regimen, and choice of RMIA. All RMIA are driven by overactivity of proinflammatory pathways, but the dominant molecules differ among the models. Hence, as with the human clinical experience, the efficacy of various antiarthritic molecules differs among RMIA, especially when the agent is a specific cytokine inhibitor.

Interleukin-1alpha induction of tensile weakening associated with collagen degradation in bovine articular cartilage

OBJECTIVE

To determine whether interleukin-1alpha (IL-1alpha) induces tensile weakening of articular cartilage that is concomitant with the loss of glycosaminoglycans (GAGs) or the subsequent degradation of the collagen network.

METHODS

Explants of young adult bovine cartilage obtained from the superficial (including the articular surface), middle, and deep layers were cultured with or without IL-1alpha for 1 week or 3 weeks. Then, portions of the explants were analyzed for their tensile properties (ramp modulus, strength, and failure strain); other portions of explants and spent culture medium were analyzed for the amount of GAG and the amount of cleaved, denatured, and total collagen.

RESULTS

The effect of IL-1alpha treatment on cartilage tensile properties and content was dependent on the duration of culture and the depth of the explant from the articular surface. The tensile strength and failure strain of IL-1alpha-treated samples from the superficial and middle layers were lower after 3 weeks of culture, but not after 1 week of culture. However, by 1 week of culture, IL-1alpha had already induced release of the majority of tissue GAGs into the medium, without detectable loss or degradation of collagen. In contrast, after 3 weeks of culture, IL-1alpha induced significant collagen degradation, as indicated by the amount of total, cleaved, or denatured collagen in the medium or in explants from the superficial and middle layers.

CONCLUSION

IL-1alpha-induced degradation of cartilage results in tensile weakening that occurs subsequent to the depletion of GAG and concomitant with the degradation of the collagen network.

Anakinra: review of recombinant human interleukin-I receptor antagonist in the treatment of rheumatoid arthritis

BACKGROUND

Interleukin-1 (IL-1) plays an important role in the pathophysiology and progression of rheumatoid arthritis (RA) by contributing to destruction of cartilage, bone, and periarticular tissues. Inhibiting IL-1 synthesis or activity with the use of recombinant human IL-1 receptor antagonist (anakinra) may prove to be an effective approach to the treatment of RA.

OBJECTIVE

The purpose of this article is to review the effects of anakinra in the treatment of RA.

METHODS

A MEDLINE search from 1982 to 2003 was used to identify animal studies and randomized clinical trials of anakinra and other therapies that target IL-1.

RESULTS

Clinical trials of anakinra have shown that it reduces the signs and symptoms of active disease and slows the rate of radiographic destruction in adults with RA. With anakinra 150 mg/d, 43% of patients achieved an American College of Rheumatology (ACR) 20% response, compared with 27% with placebo (P = 0.014). The ACR20 score indicates at least 20% improvement in the ACR composite score, which includes assessment of tender and swollen joint count, and other clinical end points such as pain and disability assessment. Patients treated with anakinra also experienced a 59% reduction in new bony erosion compared with controls (P < 0.001) and a 65% reduction in joint space narrowing as measured by the modified Sharp score (P = 0.020). Injection-site reactions were the most commonly reported adverse event, occurring in 50%, 73%, and 81% of patients receiving anakinra 30, 75, and 150 mg/d, respectively, compared with 25% of patients receiving placebo. Few serious adverse events were reported, and they typically occurred in patients receiving the highest daily dosage.

CONCLUSIONS

IL-1 is an important cytokine in promoting the damage associated with RA. Anakinra is mildly to moderately effective and well tolerated in patients with active RA when used as monotherapy or in combination with methotrexate.

The modulation of intra-articular inflammation, cartilage matrix and bone loss in mono-articular arthritis induced by heat-killed Myobacterium tuberculosis

Inflammation models for the assessment of anti-rheumatic drug activity utilize a variety of stimuli and sites. However, the determination of cartilage and bone degradation remains time consuming and problematic. A rapid rat model of Mycobacterium tuberculosis monoarticular arthritis with induces of inflammation, as well as patellar cartilage proteoglycan and bone degradation has been reported. This study characterizes this model with respect to the actions of anti-rheumatic drugs. Dexamethasone, cyclosporin and prednisolone inhibited all three parameters. Methotrexate inhibited joint inflammation alone, whilst azathioprine was without effect. Levamisole inhibited cartilage and bone degradation without affecting joint inflammation. NSAIDs were divided in their actions. Naproxen, piroxicam, diclofenac and tiaprofenic acid all inhibited joint inflammation and bone loss, but naproxen and piroxicam both significantly potentiated cartilage proteoglycan loss. This model appears to rely on cellular recruitment at this early stage, the anti-metabolites being ineffective. The modulation of inflammation can result in a protection against cartilage and bone damage in arthritis; however, certain NSAIDs are detrimental to cartilage integrity. The pharmacological manipulation of inflammatory arthritis can therefore dislocate inflammation from its effects on tissue destruction.

DA-7911, 188Rhenium-tin colloid, as a new therapeutic agent of rheumatoid arthritis

Radiation synovectomy is one of the most useful methods for treating patients with refractory synovitis because of its convenience, long-term effects, repeatability and the avoidance of surgery. In this study, we investigated the toxicity, stability and biodistribution of a rhenium-188 (188Re)-tin colloid to evaluate its suitability as a synovectomy agent. Twenty four hours after injecting the 188Re-tin colloids (74 KBq/0.1 mL) into the tail vein of ICR mice, most of the 188Retin colloidal particles was found in the lungs. In addition, there were no particle size changes at either room temperature or at 37 degrees C after injecting the 188Re-tin colloids in human plasma and synovial fluid. In vitro stability tests showed that the 188Re-tin colloid remained in a colloidal form without a critical size variation over a 2-day period. We investigated the leakage of 188Retin colloids from the intraarticular injection site with gamma counting in New Zealand white rabbits. The 188Re-tin colloids (55.5 MBq/0.15 mL) were injected at the cavum articular and the mean retention percentage of the 188Re-tin colloid was 98.7% for 1 day at the injection site, which suggests that there was neither change in the particle size nor leakage at the injection sites. In the biodistribution study with the SD rats, the liver showed the highest radioactivity (0.0427% ID/organ) except for the injected knees (99.49%). In the SD rats, mild toxicities including the skin or a synovium inflammation were observed as a result of a radioactivity of 15 mCi/kg at the intraarticular injection site. However, there was no systemic toxicity. In the Ovalbumin (OVA)-induced arthritic rabbits, the 188Re-tin colloid improved the macroscopic, the histological score and reduced the knee joint diameter when compared to the arthritic control. In conclusion, a 188Re-tin-colloid is considered as a strong candidate for radiation synovectomy with a superior efficacy and safety.

Effects of low-dose, noncytotoxic, intraarticular liposomal clodronate on development of erosions and proteoglycan loss in established antigen-induced arthritis in rabbits

OBJECTIVE

To assess the clinical and histologic effects of an intraarticular application of low-dose (non-cytotoxic) liposomal clodronate in established antigen-induced monarthritis (AIA) in rabbits.

METHODS

AIA was monitored by assessments of joint swelling, C-reactive protein levels, and radiographic changes in 17 NZW rabbits for 8 weeks during the course of weekly intraarticular injections of liposomal clodronate (0.145 mg/injection, low dose) or "empty" liposomes. The contralateral knee was injected with liposome buffer alone as the control. End-point analyses included macroscopic joint examination, immuno- and TUNEL staining, Safranin O staining/microspectrophotometry, and tumor necrosis factor alpha (TNFalpha) convertase enzyme (TACE) inhibition assay.

RESULTS

Liposomal clodronate-treated rabbits showed a reduction and delay in joint swelling during the first 3 injections. Expression of matrix-bound (solubilized) TNFalpha, lining cell hyperplasia, and levels of RAM-11+ macrophages were low in the synovium of the liposomal clodronate treatment group, but the proportion of apoptotic lining cells was not affected. The radiologic score was low at the end of weeks 2 and 4, but at 8 weeks, no difference, compared with controls, was found in pannus formation or in the extent of joint erosion; also, joint swelling was higher than before initiation of treatment. Injections of liposomal clodronate prevented cartilage proteoglycan loss, which was significant in the superficial zone only. TACE activity was not inhibited by clodronate.

CONCLUSION

Liposomal clodronate had temporary antiinflammatory and antierosive effects on established AIA in rabbits. Over the long-term, the loss of cartilage proteoglycans was halted. This observed treatment effect may be related to the inhibition of TNFalpha production and processing in the synovium.

Early degradation of type IX and type II collagen with the onset of experimental inflammatory arthritis

OBJECTIVE

To determine whether following the onset of intraarticular inflammation, there is early damage to articular cartilage, specifically to types II and IX collagen, and the proteoglycan (PG) aggrecan, and whether measurement of the degradation products of these molecules in synovial fluid (SF) and serum may permit the detection of cartilage damage.

METHODS

A rabbit model of rheumatoid arthritis, antigen (ovalbumin)-induced arthritis, was studied. Articular cartilage samples were analyzed by immunoassays for total type II collagen content, its denaturation and cleavage by collagenases, and for type IX collagen content. PG content was determined by colorimetric assay. In serum and SF, total PG content and collagenase-generated peptides of type II collagen were measured.

RESULTS

After 6 days, both the PG content and the NC4 domain of type IX collagen were reduced in femoral and tibial cartilage, concomitant with the onset of arthritis. In only the tibial cartilage did this reduction in PG persist up to day 20. However, denatured type II collagen was increased in all cartilage samples, but only on day 20. In SF, the PG content was significantly reduced on day 20, and products of type II collagen cleavage by collagenase were significantly increased on both day 6 and day 20.

CONCLUSION

This study, which is the first of its kind examining changes in both types II and IX collagen and PG content, reveals early damage to both types of collagen as well as to PG in articular cartilage samples following induction of joint inflammation. SF analyses reveal this early damage and may be of value in the study and treatment of inflammatory arthritic diseases such as rheumatoid arthritis.

Development and aging of the articular cartilage of the rabbit knee joint: Distribution of biglycan, decorin, and matrilin-1

We determined the distributions of the small proteoglycans biglycan and decorin and the glycoprotein matrilin-1 (cartilage matrix protein) during development and aging of articular cartilage in the rabbit knee joint. Before cavitation, the matrices of the interzone and the adjacent epiphyseal cartilage do not contain biglycan or decorin, but some chondrocytes express their mRNAs. Matrilin-1 is found only in the deeper epiphyseal cartilage. After cavitation, biglycan and decorin are detected in the presumptive articular cartilage, but there is no matrilin-1. All are present in the underlying epiphyseal cartilage. In the neonate, the epiphyseal cartilage is ossified and the articular cartilage becomes a discrete layer. Biglycan and decorin accumulate in the articular cartilage, but matrilin-1 remains confined to the residual epiphyseal cartilage. In the adult, the distributions of biglycan and decorin are highly variable. Decorin tends to be confined to the central region; matrilin-1 is absent. The findings indicate that the articular and epiphyseal cartilages are different from the earliest developmental stages. The epiphyseal cartilage can be identified by its possession of matrilin-1. Epiphyseal cartilage is removed during development to leave the articular cartilage. The relationships between the distributions of decorin and matrilin-1 and the fibrillar collagens are discussed. (J Histochem Cytochem 47:1603-1615, 1999)

Interleukin-1 receptor antagonist

There are three members of the IL-1 gene family: IL-1 alpha, IL-1 beta, and IL-1ra, IL-1 alpha, and IL-1 beta are both antagonist molecules with many proinflammatory effects. IL-1ra is an antagonist molecule that can inhibit the effect of IL-1 alpha and IL-1 beta by specifically blocking the IL-1 receptor on target effector cells. IL-1 alpha and IL-1 beta are considered to be pivotal cytokines in the pathogenesis of many inflammatory diseases. Anti-IL-1 treatment has been shown to cause amelioration of arthritis in animal models and in RA, suggesting that IL-1ra may be an important therapeutic option in the future management of RA.

Isothiazolones interfere with normal matrix metalloproteinase activation and inhibit cartilage proteoglycan degradation

A series of isothiazolones that inhibit pro-(matrix metallo-proteinase) (proMMP) activation but do not inhibit the active enzyme are effective as cartilage protectants in bovine nasal cartilage organ culture, preventing interleukin-1 (IL-1)-induced proteoglycan (aggrecan) degradation without affecting its synthesis. These compounds were found to bind to prostromelysin (proMMP-3) in a non-dialysable and stoichiometric manner. Preincubation with cartilage-protectant isothiazolones prevented the binding of [14C]iodoacetamide to Cys75 of the MMP-3 propeptide, suggesting that the activity of these compounds involves their binding to the Cys75 of the MMP zymogen. Studies following chymotrypsin activation of proMMP-3 by SDS/PAGE indicated that altered processing of the 57 kDa zymogen to the active form occurred in the presence of compound. The 53 kDa intermediate seen on normal activation was not formed; instead a different intermediate appeared with a molecular mass of approx. 46 kDa. N-terminal sequence analysis indicated that this intermediate was formed by cleavage at the putative 4-aminophenylmercuric acid cleavage site. Importantly the 45 kDa active MMP-3 species formed in the presence of compound was one amino acid residue shorter than the native MMP-3. These results suggest that the inhibition of cartilage proteoglycan degradation by isothiazolones might be due to their ability to bind to the Cys75 in the propeptide region of the MMP zymogen and interfere with its normal activation process.

Biochemical markers in synovial fluid identify early osteoarthritis of the glenohumeral joint

The objective of this study on the glenohumeral joint was to assess the (1) accuracy of clinical diagnosis of osteoarthritis compared with arthroscopic diagnosis, and (2) the ability of biochemical markers in synovial fluid to detect osteoarthritis. Patients (96) were examined clinically and the preoperative diagnosis of osteoarthritis was recorded. At surgery (arthroscopy or arthroplasty), the glenohumeral joint was inspected for signs of osteoarthritis, and the joint osteoarthritis grade (I-IV) was recorded. At surgery, synovial fluid lavage was obtained from the joint, and later analyzed to determine levels of aggrecan components: total sulfated glycosaminoglycan and keratan sulfate epitope, link protein and the chondroitin sulfate epitope recognized by antibody 3B3 (3B3(-)). Compared with arthroscopic diagnosis of osteoarthritis, the results showed that the clinical diagnosis did not wrongly identify joints without osteoarthritis, and was always able to identify joints with advanced (Grade IV) osteoarthritis. Grade II osteoarthritis was rarely identified (10% of the time), and Grade III osteoarthritis was identified 50% of the time. Biochemical assessment of the synovial fluid showed that the catabolic markers (sulfated glycosaminoglycan, keratan sulfate and link protein) were elevated in fluids from joints with moderate (Grade III) and advanced osteoarthritis (Grade IV), and the 3B3(-) epitope was elevated in Grades II, III, and IV. These results show that arthroscopic diagnosis for osteoarthritis, of the glenohumeral joint is particularly useful for early and moderate osteoarthritis, where clinical (nonarthroscopic) diagnosis is poor, and that biochemical analysis of the synovial fluids corresponds well to arthroscopic diagnosis of shoulder osteoarthritis.

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.

The effects of the phospholipase A2 inhibitor, manoalide, on cartilage degradation, stromelysin expression, and synovial fluid cell count induced by intraarticular injection of human recombinant interleukin-1 alpha in the rabbit

OBJECTIVE

To evaluate the effects of the phospholipase A2 (PLA2) inhibitor manoalide on cartilage degradation, stromelysin expression, and inflammatory cell accumulation in rabbits treated intraarticularly with recombinant human interleukin-1 alpha (rHuIL-1 alpha).

METHODS

Rabbits were given an intraarticular injection of rHuIL-1 alpha. At various time points over a 24-hour period, the rabbits were euthanized and the articular space was lavaged with sterile PBS. The proteoglycan content of the lavage fluid was measured using a dimethylmethylene blue assay. PLA2 activity and differential cell counts were also measured. The femur was removed and cartilage proteoglycan content determined. In some experiments, levels of synovial stromelysin messenger RNA (mRNA) were assessed. Manoalide or vehicle was administered 30 minutes before the rHuIL-1 alpha injection.

RESULTS

The rHuIL-1 alpha-induced arthritic response is characterized by significant accumulation of inflammatory cells, loss of proteoglycan from the condylar cartilage, and induction of mRNA for stromelysin. PLA2 activity was also elevated in synovial fluids from rHuIL-1 alpha-injected joints. Pretreatment with manoalide (0.3 mg/joint) significantly inhibited PLA2 activity in the synovial fluid, prevented the loss of proteoglycan from the condylar cartilage, and reduced proteoglycan levels in lavage fluids. However, manoalide either had no effect on, or stimulated, cell accumulation. To assess the relationship between the induction of PLA2 and stromelysin, levels of stromelysin mRNA were measured in synovial tissue from manoalide- and vehicle-treated joints. Stromelysin message levels were significantly suppressed in a dose-dependent manner.

CONCLUSION

These studies demonstrate that manoalide is a potent inhibitor of inflammation and cartilage catabolism, and suggest that PLA2 is involved in the pathophysiology of rHuIL-1 alpha-induced arthritis in rabbits.

Changes in cartilage proteoglycan aggrecan after intra-articular injection of interleukin-1 in rabbits: studies of synovial fluid and articular cartilage

OBJECTIVE

To determine how acute but transient inflammation affects the cartilage proteoglycan aggrecan and the value of analyses of synovial fluid to study this.

METHODS

For 96 hours after a single intra-articular injection of rabbit knees with human interleukin-1 alpha (IL-1 alpha) or vehicle, articular cartilage and synovial fluid were examined using a putative indicator of aggrecan synthesis (aggrecan chondroitin sulphate epitope 846), immunoreactive keratan sulphate, and total glycosaminoglycan (GAG) content. Aggrecan extractability (with 0.5 M NaCl) followed by 4 M guanidine hydrochloride extraction permitted analyses of cartilage damage, total content and aggrecan heterogeneity. Aggrecan epitopes as well as GAG were assayed in synovial fluid. Changes were related to total joint leucocyte content in synovial fluid.

RESULTS

At 10 ng, IL-1 alpha produced a transient increase in synovial fluid leucocytes at six hours and 24 hours. This accompanied a reduction in content and increased extractability of GAG, which was greatest in the tibial medial compartment of the knee. Further studies of this compartment showed no change in keratan sulphate epitope content, but a transient increase in extractability in 0.5 M NaCl. Epitope 846 content and extractability were unchanged. Total contents and extractability for GAG were inversely correlated in both controls and joints injected with IL-1 alpha. These changes were accompanied by transient increases in GAG, keratan sulphate epitope, and 846 content in synovial fluid.

CONCLUSION

According to the aggrecan component measured, damage to the matrix of articular cartilage was sometimes reflected by a transient increased extractability and a net loss of aggrecan. There was always an increased release of GAG, and keratan sulphate, and 846 epitopes into synovial fluid. These studies show that changes in aggrecan epitopes and GAG in synovial fluid reflect changes in cartilage metabolism induced by acute transient inflammation.

2,5-Diarylisothiazolone: novel inhibitors of cytokine-induced cartilage destruction

A series of 2,5-diarylisothiazolones is reported that inhibit the IL-1 beta-induced breakdown of bovine nasal septum cartilage in an organ culture assay. The synthesis and preliminary SAR of these compounds are described. These compounds represent a novel, nonpeptide lead series approach to the mediation of the chronic cartilage breakdown associated with arthritic disease. These compounds are relatively resistant to reductive metabolism by liver microsomal preparations and appear to inhibit cartilage breakdown by interfering with the proteolytic activation of matrix metalloproteinases.

Signal transduction through chondrocyte integrin receptors induces matrix metalloproteinase synthesis and synergizes with interleukin-1

OBJECTIVE

To study the role of signal transduction via integrin receptors in the production of metalloproteinase by rabbit articular chondrocytes.

METHODS

Confluent, primary rabbit articular chondrocytes (RAC) were incubated for 72 hours in the presence of interleukin-1 (IL-1), Arg-Gly-Asp (RGD) peptide, or a combination of IL-1 and RGD peptide. Media were analyzed for stromelysin enzymatic activity using a 3H-labeled transferrin substrate, and for stromelysin and collagenase protein by Western analysis. Gelatinase activity was analyzed by gelatin zymography. IL-1 receptor antagonist (IL-1Ra) protein was used to determine the involvement of IL-1 in mediating the effects of RGD peptide, and fluorescence-activated cell sorter analysis (FACS) was used to examine the effect of IL-1 on chondrocyte integrin subunit expression.

RESULTS

RGD peptides induced chondrocyte synthesis of stromelysin, collagenase, and 92-kd gelatinase B, and increased synthesis of the constitutively expressed 72-kd gelatinase A. Further studies focusing on stromelysin demonstrated that this up-regulation was concentration dependent and that RGD peptides synergized with IL-1 in inducing stromelysin synthesis. RGD-induced stromelysin production was inhibited by the IL-1Ra in a concentration-dependent manner, indicating that induction by RGD requires binding of IL-1 to its receptor. FACS analysis of RAC showed that IL-1 stimulation increased the expression of beta 1 and alpha v integrin subunits on the chondrocyte surface.

CONCLUSION

Our data demonstrate that signal transduction through chondrocyte integrin receptors up-regulates metalloproteinase expression and that this is likely mediated through induction of IL-1. They also suggest that the binding of adhesion molecules to their chondrocyte integrin receptors reduces the amount of IL-1 required to induce stromelysin synthesis. Up-regulation of chondrocyte integrin expression by IL-1 may play a role in the synergistic effects seen with a combination of IL-1 and RGD peptides. Since elevated levels of both IL-1 and adhesion molecules are present in rheumatoid arthritis and osteoarthritis synovial fluid, our data suggest that this interaction may be important in mediating the cartilage destruction accompanying these diseases.

Even low-grade synovitis significantly accelerates the clearance of protein from the canine knee. Implications for measurement of synovial fluid "markers" of osteoarthritis

OBJECTIVE

In recent studies, the synovial fluid concentration of molecules derived from the extracellular matrix of articular cartilage has been used to deduce the magnitude of cartilage destruction or repair in osteoarthritic (OA) joints. Because low-grade synovitis is often present in such joints, we assessed the effect of synovial inflammation on the clearance of a prototypical protein, albumin, from synovial fluid.

METHODS

131I-labeled albumin (RISA) was injected into 1 (control) knee of each of 14 dogs. The concentration of RISA in synovial fluid aspirated 7 hours after the injection and serial measurements of surface radioactivity were used to calculate the volume of distribution (Vd) and clearance of RISA. One week later, synovitis was induced in the contralateral knee by intraarticular injection of various quantities of calcium pyrophosphate dihydrate (CPPD) crystals, after which RISA was injected into that joint and these measurements were repeated.

RESULTS

Intraarticular injection of 500 micrograms of CPPD crystals produced intense synovitis, with a mean synovial fluid white blood cell (WBC) count of 43,200 cells/mm3, and values for RISA Vd and RISA clearance (36.5 ml and 33.7 microliters/minute) were much higher than those for saline-injected control knees (2.7 ml and 1.5 microliters/minute, respectively). Injection of 0.5 microgram of CPPD also produced marked synovitis and values for Vd and RISA clearance that were 2-3-fold greater than those in the contralateral knee. The low-grade synovitis produced by only 0.05 microgram of CPPD, which resulted in synovial fluid WBC counts as low as 1,000-2,000 cells/mm3, was accompanied by increases in the clearance and Vd of RISA to levels approximately 40% and approximately 80% higher, respectively, than those for the contralateral knee.

CONCLUSION

Even mild synovitis, as seen in OA, may significantly increase the clearance of a protein from the joint. Synovitis is a significant variable which must be considered in studies of putative chondroprotective drugs if conclusions about the effects of drugs on cartilage metabolism are to be drawn from changes in the synovial fluid concentration of a "marker" protein.

Pathogenesis of degenerative joint disease in the human temporomandibular joint

The wide range of disease prevalences reported in epidemiological studies of temporomandibular degenerative joint disease reflects the fact that diagnoses are frequently guided by the presence or absence of non-specific signs and symptoms. Treatment is aimed at alleviating the disease symptoms rather than being guided by an understanding of the underlying disease processes. Much of our current understanding of disease processes in the temporomandibular joint is based on the study of other articular joints. Although it is likely that the molecular basis of pathogenesis is similar to that of other joints, additional study of the temporomandibular joint is required due to its unique structure and function. This review summarizes the unique structural and molecular features of the temporomandibular joint and the epidemiology of degenerative temporomandibular joint disease. As is discussed in this review, recent research has provided a better understanding of the molecular basis of degenerative joint disease processes, including insights into: the regulation of cytokine expression and activation, arachidonic acid metabolism, neural contributions to inflammation, mechanisms of extracellular matrix degradation, modulation of cell adhesion in inflammatory states, and the roles of free radicals and heat shock proteins in degenerative joint disease. Finally, the multiple cellular and molecular mechanisms involved in disease initiation and progression, along with factors that may modify the adaptive capacity of the joint, are presented as the basis for the rational design of new and more effective therapy.

Antifibrotic action of interleukin-1 receptor antagonist in lapine monoarticular arthritis

OBJECTIVE

To determine if the administration of interleukin-1 receptor antagonist (IL-1ra) to animals with established antigen induced arthritis had any beneficial effects on the synovitis and cartilage destruction.

METHODS

Antigen induced arthritis was induced in New Zealand White rabbits, and after two weeks IL-1ra was administered every six hours over a 72 hour period. Animals were then killed and joint tissues examined for the degree of synovitis, synovial fibrosis, and cartilage damage.

RESULTS

The response of the arthritis to the treatment was minor in terms of joint swelling, leucocyte accumulation, or cartilage proteoglycan loss. However, the synovial fibrosis was not only halted by administration of IL-1ra, but reversed. The inflamed synovial linings of IL-1ra treated animals showed a significant loss of synovial collagen content and a reappearance of the synovial fat spaces which are prominent in the normal synovial lining.

CONCLUSION

This study shows that IL-1ra has potent antifibrotic activity and suggests the use of this agent for the reversal of the fibroproliferative process which is so important in the pathology of rheumatoid arthritis.

Metabolism resistant isothiazolone inhibitors of cartilage breakdown

A series of 2-(arylmethyl)pyridoisothiazolones is reported that inhibit the IL-1 beta induced breakdown of bovine nasal septum cartilage in an organ culture assay. The synthesis and preliminary SAR of these compounds are described. These compounds represent a novel, non-peptide lead series approach to the mediation of the chronic cartilage breakdown associated with arthritic disease. These compounds are relatively resistant to reductive metabolism by liver microsomal preparations and appear to inhibit cartilage breakdown by interfering with the proteolytic activation of matrix metalloproteinases.

Evaluation of treatment modalities for septic arthritis with histological grading and analysis of levels of uronic acid, neutral protease, and interleukin-1

We compared the effectiveness of antibiotics alone and in combination with arthroscopy, arthroscopy with debridement, arthrotomy, or needle aspiration for the treatment of septic arthritis. Each modality has its proponents, but, to our knowledge, no comparative studies have been conducted in animals. We used biochemical and histological analysis to compare these methods of treatment in an experimental model. The right hind knee of thirty goats was injected with 1 x 10(5) Staphylococcus aureus bacilli. The left hind knee was not inoculated and served as the normal control. Seventy-two hours after inoculation, a two-week course of treatment with intramuscular administration of cefuroxime sodium, either alone or in combination with another mode of treatment, was initiated in each of five groups. The cartilage was evaluated histologically with biochemical, enzymatic, and interleukin-1 analyses. Despite the early therapeutic intervention, on the average, there was a 25 per cent loss of uronic acid (t test, p < 0.001) and a 43 per cent increase in neutral protease activity (signed-rank test, p = 0.003) in the treatment groups. There were no significant intergroup differences with regard to the histochemical-histological rating or the levels of uronic acid, neutral protease, or interleukin-1.

A simple in vivo model of collagen degradation using collagen-gelled cotton buds: the effects of collagenase inhibitors and other agents

A simple in vivo model of collagen degradation has been developed, and the effects of various agents have been tested. Type I collagen was prepared from rat skin and acetylated with either [3H]- or [14C] acetic anhydride. The radiolabelled collagen was added to sterile cotton buds and incubated at 37 degrees C to allow the collagen to form native fibrils that were firmly adsorbed to the cotton matrix. After subcutaneous implantation of the collagen-gelled cotton buds into rats, the radiolabelled collagen was progressively removed over a period of weeks by an infiltrating granuloma. Of the agents that were administered directly into the cotton buds using subcutaneously implanted osmotic mini-pumps, only the synthetic collagenase inhibitors CI-A (containing a hydroxamate moiety as a zinc ligand) and CI-C (containing a thiol moiety as a zinc ligand) were able to prevent the removal of collagen: their efficacy correlated with the level of collagenase inhibitory activity assayed in the exudate fluid sequestered within the cotton bud granuloma. Of the agents that were administered systemically, including anti-inflammatory drugs and other compounds used as therapies for arthritis, only hydrocortisone was able to inhibit the removal of radiolabelled collagen. These results suggest that, in this model, interstitial collagenase, a member of the matrix metalloproteinase family, comprised the major degradative pathway for collagen. The collagen-gelled cotton bud model is a useful test system for delineating those processes that result in collagen catabolism. In addition, the model can be used for testing agents, including those of limited or unknown systemic bioavailability, in order to discover novel therapeutic agents for preventing collagen degradation in connective tissue diseases such as arthritis.

Different immunological mechanisms contribute to cartilage destruction in antigen-induced arthritis

Antigen-induced arthritis in guinea pigs was used as a model to investigate the pathogenic mechanisms responsible for cartilage destruction in chronic joint inflammation. The activation of macrophages, their effects on cartilage metabolism, and the development of autoimmunity to cartilage constituents were studied during the progression of arthritis. The results show that in arthritic animals the macrophages are systemically activated, with a peak in the early phase of inflammation. Interleukin 1, produced by the activated cells, suppresses the proteoglycan synthesis in cartilage explants and cultured chondrocytes and increases the proliferation of the cells in vitro. During the progression of arthritis humoral and cell-mediated immune responses to collagen type II and cartilage proteoglycans occur correlating with the severity of arthritis. It is concluded that different immunological mechanisms may be involved in cartilage destruction during antigen-induced arthritis. Mediator-induced metabolic reactions dominate in the early phase, whereas autoimmunity to cartilage might play an essential role in later phases of arthritis.

In vivo protection against interleukin-1-induced articular cartilage damage by transforming growth factor-beta 1: age-related differences

OBJECTIVES

Transforming growth factor-beta (TGF-beta) has been shown to antagonise interleukin-1 (IL-1) effects in different systems. Investigations were carried out to study whether TGF-beta 1 modulates IL-1 induced inflammation and IL-1 effects on articular cartilage in the murine knee joint.

METHODS

IL-1, TGF-beta 1 or both factors together were injected into the knee joint. Inflammation was studied in whole knee histological sections. Patellar cartilage proteoglycan synthesis was measured using 35S-sulphate incorporation while patellar cartilage glycosaminoglycan content was determined with automated image analysis on joint sections.

RESULTS

Co-injection of TGF-beta 1 and IL-1 resulted in synergistic attraction of inflammatory cells. In contrast, TGF-beta 1 counteracted IL-1 induced suppression of articular cartilage proteoglycan synthesis. Proteoglycan depletion was similar shortly after the last injection of IL-1 or IL-1/TGF-beta 1, but accelerated recovery was found with the combination at later days. This protective effect of TGF-beta 1 could not be demonstrated in older mice.

CONCLUSIONS

TGF-beta 1 aggravates IL-1 induced knee joint inflammation, but counteracts the deleterious effects of IL-1 on articular cartilage proteoglycan synthesis and content. The data indicate that TGF-beta 1 could play an important part in articular cartilage restoration after IL-1 induced proteoglycan depletion.

Differential levels of synovial fluid aggrecan aggregate components in experimental osteoarthritis and joint disuse

The levels of proteoglycan aggregate components (link protein, keratan sulfate epitope, and total sulfated glycosaminoglycan) were determined in the synovial fluid lavages of dogs with experimental osteoarthritis or disuse atrophy. A model of experimental osteoarthritis was created by transection of the anterior cruciate ligament of the right knee; studies were carried out 6 and 12 weeks after surgery. Joint disuse was studied at 4 and 8 weeks after initiation of the disuse. Recovery after disuse also was studied in joints that had 3 weeks of remobilization after 4 or 8 weeks of disuse. Synovial fluid lavages from the right knee joints of untreated animals were used as controls. The concentrations of keratan sulfate epitope, sulfated glycosaminoglycan, and link protein in the synovial fluid lavages at 6 and 12 weeks after transection of the anterior cruciate were elevated compared with the control values. Similar analysis of the fluid after disuse showed that the levels of keratan sulfate epitope and sulfated glycosaminoglycan were increased compared with the control levels and the levels after transection. However, the concentration of link protein in the fluid after disuse was not significantly different from the control level. The levels of keratan sulfate epitope and sulfated glycosaminoglycan in the synovial fluid lavages after disuse with recovery were high, but the levels of link protein remained low. The results indicate that the catabolism of proteoglycan aggregates in articular cartilage during early osteoarthritis and disuse is different. The determination of keratan sulfate epitope in synovial fluid lavages appears to provide a relatively general indication of proteoglycan catabolism, whereas increased levels of link protein may be more indicative of cartilage degeneration.

Animal models for osteoarthritis: processes, problems and prospects

Images

Effect of animal age and chronicity of interleukin-1 exposure on cartilage proteoglycan depletion in vivo

Rheumatoid arthritis and osteoarthritis are characterized by an early depletion of cartilage proteoglycans, which leads to a decrease in cartilage compressibility and, eventually, to a loss of joint function. Interleukin-1, which is thought to have a role in mediating this loss of proteoglycans in arthritis, induces an acute depletion of proteoglycans from articular cartilage following intra-articular injection in rabbits. As the structure and metabolism of proteoglycans are known to change with age, my laboratory investigated the effect of age on depletion and recovery of proteoglycans in response to interleukin-1 in the rabbit. Loss of cartilage proteoglycans induced by interleukin-1 was less severe in immature animals, increased until the age of sexual maturity, and then remained constant. The rate of recovery and compensatory overshoot in the rate of proteoglycan synthesis following challenge with interleukin-1 was more rapid in immature animals and may have been responsible for the quicker return of the cartilage proteoglycan content to control levels in younger animals. With multiple exposures to interleukin-1 at time intervals too short for recovery to occur, smaller amounts of interleukin-1 induced loss of proteoglycans, and the proteoglycan content and the rate of synthesis remained depressed longer after treatment had stopped. The decreased ability of mature cartilage to replace proteoglycans rapidly after exposure to cytokines would increase the probability of subsequent inflammatory episodes before recovery is complete; this may result in increased susceptibility of adult cartilage to proteoglycan depletion.

Cloning and expression in Escherichia coli of the gene encoding the Proteus vulgaris chondroitin ABC lyase

The structural gene encoding chondroitin ABC lyase from Proteus vulgaris was cloned and sequenced. This gene consists of a single open reading frame of 3,063 bp, including a sequence (72 bp) for a possible secretory protein leader peptide, preceded by a Shine-Dalgarno ribosomal binding site. Promoter-like and rho-independent terminator sequences were detected upstream and downstream of the open reading frame, respectively. The G+C content of the coding region was 38.6%. The transcription startpoint was located 41-bp upstream of the initiation codon (ATG). Chondroitin ABC lyase is composed of 997 amino acids, and has a relative molecular mass of 112,635. When the 5.2-kb fragment containing the 1.2-kb upstream from the gene was inserted into pSTV29, and cloned in Escherichia coli, chondroitin ABC lyase was induced in the medium containing chondroitin-6-sulfate as the carbon source. On the other hand, when a 4.2-kb fragment containing only 0.2 kb upstream was inserted into pSTV29(pCHS delta 6), and pCHS delta 6 was introduced into E. coli, the enzyme was constitutively produced, even in medium containing glucose as the carbon source. By immunoblot analysis, the polypeptide synthesized by E. coli cells carrying pCHS delta 6 appeared to be the same as that of the purified chondroitin ABC lyase from P. vulgaris.

Production of IL-1 and IL-1 receptor antagonist and the pathological significance in lipopolysaccharide-induced arthritis in rabbits

Injection of lipopolysaccharide (LPS) into rabbit knee joints provoked leucocyte infiltration and loss of proteoglycan (PG) from the cartilage. We investigated the role of IL-1 and IL-1 receptor antagonist (IL-1Ra) and its significance in the pathogenesis of LPS-arthritis. Production of IL-1 beta peaked at 6 h (196.7 +/- 89.4 pg/joint) after injection of 10 ng of LPS, while IL-1Ra peaked at 9 h (34.5 +/- 13.4 ng/joint). The amount of IL-1Ra was 180-200-fold molar excess of IL-1, and a large amount of IL-1Ra was sustained for 1 week. Both IL-1 beta and IL-1Ra were mainly produced by synovial exudate cells. Arthritis was reproduced by rabbit IL-1 beta. LPS-induced leucocyte infiltration was inhibited 70-75% by rabbit IL-1Ra. Loss of PG in LPS-arthritis was prevented by IL-1Ra and also by neutrophil elastase inhibitor, and superoxide dismutase. In leucopenic rabbits, injection of LPS induced neither production of IL-1 beta nor loss of PG. Direct injection of inflammatory exudated cells in leucopenic rabbits reproduced loss of PG, and there was only a partial recovery by IL-1Ra. These results suggest that LPS-initiated IL-1 acts as a key mediator in LPS-arthritis and that endogenous IL-1Ra may suppress a part of IL-1 activity at the site, but its amount was too low for suppression of the produced IL-1. Loss of PG is a sequela of infiltrated leucocytes and leucocyte-derived elastase, and superoxide anion may play a pivotal role in the destruction of cartilage.

Toxicity of complement for chondrocytes. A possible source of cartilage degradation in inflammatory arthritis

Cartilage from patients with rheumatoid arthritis and from animals with antigen-induced arthritis is frequently contaminated with complement-containing immune complexes. A possible role for complement activation in cartilage degradation was modeled in vitro by exposing cultured bovine chondrocytes to homologous serum, and determining cytotoxicity by monitoring the release of intracellular 51Cr. Complement activation was found to be cytotoxic, having maximal effect at 20-30% serum by 18 h. Serum toxicity was ablated by heat (50 degrees C, 20 min) or methylamine treatment but not by EGTA, suggesting that in these experiments activation occurred by the alternate route. The implications of the results are discussed in relation to ultrastructural evidence for the involvement of complement in the pathogenesis of cartilage degradation in inflammatory arthritis.

The quantitation of a native chondroitin sulfate epitope in synovial fluid lavages and articular cartilage from canine experimental osteoarthritis and disuse atrophy

OBJECTIVE

Previous studies have shown the presence of a native chondroitin sulfate epitope in articular cartilage proteoglycans from canine knee joints with experimental early osteoarthritis (OA), but not in normal cartilage. The objective of this study was to quantitate the native epitope recognized by monoclonal antibody 3-B-3 in synovial fluids and articular cartilage of diseased joints.

METHODS

An immunoassay with monoclonal antibody 3-B-3, which recognizes a native chondroitin-6-sulfate structure, was developed and used to analyze synovial fluid lavage material and extracts of articular cartilage from canine knee joints with early experimental OA or with mild disuse atrophy, and from control animals.

RESULTS

The concentration of epitope in the OA fluids was elevated 33-35-fold, and in the OA articular cartilage extracts it was elevated > 200-fold, compared with samples from the control group. No significant difference was detected in the levels of 3-B-3 epitope in the synovial fluid lavage material or cartilage extracts from the joints of the disuse group versus the control group.

CONCLUSION

The native 3-B-3 epitope in articular cartilage and synovial fluids may be a specific marker of ongoing anabolic events in early degenerative joint disease.

Intrasynovial levels of sulphated glycosaminoglycans and autoantibodies to type II collagen in rheumatoid arthritis: a correlative analysis

It is uncertain whether the autoantibodies to type II collagen that occur frequently in the serum and synovial fluid of patients with rheumatoid arthritis (RA), but rarely in other articular diseases, are primary or secondary to cartilage damage. Hence, we measured antibodies in synovial fluid from patients with RA and other articular diseases and related these to the concentration of sulphated glycosaminoglycans, as a measure of ongoing cartilage catabolism. Synovial fluids from 42 patients with RA and 30 patients with other articular diseases were studied. We found that levels of antibodies to native and denatured collagen were significantly higher in RA than in all other articular diseases, whereas concentrations of sulphated glycosaminoglycans were similar. The absence of any correlation between levels of sulphated glycosaminoglycans and antibodies to collagen weighs against the occurrence of such antibodies in RA as a secondary effect of cartilage damage.

Comparison of magnetic resonance imaging (MRI) and histopathology in rabbit models of osteoarthritis and immune arthritis

Osteoarthritis was surgically induced in mature male Dutch Belted rabbits by sectioning the fibular collateral and sesamoid ligaments and removal of the anterior horn of the lateral meniscus. The site of surgical intervention was detectable by MRI. Histopathologic analysis revealed severe focal cartilage lesions on opposing surfaces of the tibia and femur. Histology of cartilage adjacent to the osteoarthritic lesions appeared normal. In another animal model, arthritis was induced by immunization against ovalbumin followed by intra-articular injection of ovalbumin. MRI of immune arthritic rabbit knees showed accumulation of synovial fluid and cartilage degradation. Histopathology was characterized by vascular necrosis of the synovium and depletion of cartilage proteoglycan. MRI can be used to non-invasively follow the therapeutic effects of drug treatment on synovial inflammation and cartilage degradation in rabbit knees.

The effect of naproxen and interleukin-1 on proteoglycan catabolism and on neutral metalloproteinase activity in normal articular cartilage in vitro

The events in inflammatory and degenerative joint diseases involve major changes in the metabolic events in the articular cartilage. The effects of nonsteroidal anti-inflammatory drugs (NSAIDs) on articular cartilage metabolism remain unclear, however. The objective of this catabolism of proteoglycans in articular cartilage explants maintained in culture. Release of proteoglycan from the cartilage was compared with release of neutral metalloproteinase activity. The effect of the drug also was determined on the IL-1-stimulated release of proteoglycan and neutral metalloproteinase activity from the explants. At concentrations that included those present in synovial fluids of patients treated with the drug, naproxen sodium was found to suppress the release of proteoglycan and neutral metalloproteinase activity from the articular cartilage extracts. This is in contrast to the well-documented effect of interleukin-1 (IL-1), which was shown to stimulate release of proteoglycan and neutral metalloproteinase activity from articular cartilage. The effect of naproxen sodium on the IL-1-stimulated release was to suppress, but not totally overcome, the increased release of proteoglycan and neutral metalloproteinase activity. In summary, these in vitro studies of cartilage metabolism indicate that naproxen sodium has the potential to suppress catabolic activities in articular cartilage, including those that are motivated by IL-1.

The role of CD18 in IL-8 induced dermal and synovial inflammation

1. The intradermal administration of endothelial IL-8 (IL-8(1-77) or monocyte derived IL-8 (IL-8(1-72) to rabbits produced a concentration-dependent increase in plasma extravasation and an accumulation of polymorphonuclear leukocytes (PMNs) when measured over a 3 h time period. When plasma extravasation and PMN accumulation were measured over a 30 min time period no significant increases in PMN accumulation or plasma extravasation were observed in response to IL-8 alone. However, under these conditions, the addition of prostaglandin E2 (100 pmol) produced a significant potentiation of IL-8-induced plasma extravasation. There was no significant difference between the biological activities of IL-8(1-77) and IL-8(1-72). 2. Plasma extravasation and PMN accumulation induced by IL-8 were inhibited in rabbits pretreated with the monoclonal antibody designated IB4 (1 mg kg-1, i.v.) directed against the common beta chain (CD18) of the leukocyte integrins. 3. The intra-articular administration to rabbits of IL-8(1-77) (1 nmol) resulted 24 h later in the appearance of a mixed population of leukocytes (PMNs and mononuclear cells) in synovial lavage fluid. Biochemical analyses revealed the presence of an increased level of sulphated proteoglycans (sPG) and of the metalloproteinase stromelysin. Pretreatment of rabbits with IB4 (3 mg kg-1, i.v.) inhibited the accumulation of PMNs but had no effect on the mononuclear infiltrate nor on the levels of sPG or stromelysin. 4. The intradermal or intra-articular injection of E. coli-derived endotoxin induced similar inflammatory changes to those observed with IL-8.The possibility that the biological activities of IL-8 were attributable to minor contamination with endotoxin is unlikely for two reasons. Firstly, biological effects of endotoxin were observed at levels greater than that contained in the IL-8 preparation. Secondly,reduction of the endotoxin content of the IL-8 preparation by a factor of 10 did not produce a concomitant reduction in the observed biological activity of the IL-8.

Substance P in the synovial membrane and fluid of the equine middle carpal joint

This preliminary study was designed to determine whether the neurotransmitter substance P was present in the middle carpal synovial membrane of the normal horse and whether the neuropeptide could be identified in the synovial fluid of normal horses and those with joint diseases. Immunocytochemistry on middle carpal synovial membrane biopsies from fresh cadavers was used to demonstrate substance P-containing neural elements. Substance P was most abundant in the subintimal portion of the membrane, with occasional filaments coursing via synovial fronds to the intimal portion. Radioimmunoassay techniques were used on acidified acetonitrile-preserved synovial fluid samples to measure substance P concentrations. Fluid from 9 joints of 5 normal horses and 6 joints of 4 horses with joint diseases were analysed. Disease conditions included acute and chronic osteoarthritis and osteochondrosis. Synovia from normal horses contained a mean concentration of substance P significantly less than that of horses with joint diseases (P less than 0.05). Elevated concentrations of neurotransmitters in diseased joints suggests a potential contribution to the pathophysiology of joint disorders in horses.

Proteoglycan fragments in joint fluid. Influence of arthrosis and inflammation

We determined the concentration of proteoglycan fragments in knee joint fluid collected from knee-ligament injured patients more than 6 months after the trauma and from patients with acute pyrophosphate arthritis and arthrosis or with arthrosis only. Injured patients with normal or only mildly altered cartilage at arthroscopy and with normal radiographs, had twice the average concentration of healthy volunteers. Other injured patients with advanced, radiographic signs of arthrosis, had synovial fluid proteoglycan fragment concentrations within the range of healthy volunteers. Patients with pyrophosphate arthritis had the highest concentrations, substantially increased compared with both arthrosis patients, with or without knee injury and healthy volunteers. Likewise, there was an inverse relation between the degree of arthrosis and the concentration of proteoglycan fragments in the joint fluid in patients with pyrophosphate arthritis and arthrosis or with arthrosis only. We conclude that synovial fluid levels of proteoglycan fragments are influenced by the mass of cartilage matrix remaining in the joint, the inflammatory activity in the joint, and the metabolic activity of the cartilage cells.

Characterization of proteoglycan degradation by calpain

Degradation of cartilage proteoglycans was investigated under neutral conditions (pH 7.5) by using pig kidney calpain II (EC 3.4.22.17; Ca(2+)-dependent cysteine proteinase). Aggregate and monomer degradation reached a maximum in 5 min at 30 degrees C when the substrate/enzyme ratio was less than 1000:1. The mode of degradation was limited proteolysis of the core protein; the size of the products was larger than that of papain-digested products and comparable with that of trypsin-digested products. The hyaluronic acid-binding region was lost from the major glycosaminoglycan-bearing region after incubation with calpain II. Calpains thus may affect the form of proteoglycans in connective tissue. Ca(2+)-dependent proteoglycan degradation was unique in that proteoglycans adsorb large amounts of Ca2+ ions rapidly before activation of calpain II: 1 mg of pig cartilage proteoglycan monomer adsorbed 1.3-1.6 mu equiv. of Ca2+ ions before activation of calpain II, which corresponds to half the sum of anion groups in glycosaminoglycan side chains. This adsorption of Ca2+ was lost after solvolysis of proteoglycan monomer with methanol/50 mM-HCl, which was used to desulphate glycosaminoglycans. Therefore cartilage proteoglycans are not merely the substrates of proteolysis, but they may regulate the activation of Ca(2+)-dependent enzymes including calpains through tight chelation of Ca2+ ions between glycosaminoglycan side chains.

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.

Microbiochemical analysis of changes in proteoglycan and collagen in joint tissues during the development of antigen-induced arthritis in the rabbit

Microbiochemical assays of the proteoglycan and collagen content of articular cartilage and synovial lining have been performed on tissue sections taken from rabbits with antigen-induced arthritis. This experimental arthritis is a close analogue of the natural disease-rheumatoid arthritis. Animals were killed at intervals during the first 21 days following induction of arthritis to assess changes in the composition of the extracellular matrices of the synovial lining and articular cartilage during the early development of this experimental lesion. In confirmation of earlier studies these microbiochemical assays revealed a rapid and significant loss of proteoglycan from the articular cartilage. This loss was, however, not uniform but was restricted to the intermediate zone of the cartilage. Over the period studied, there was only a slight loss of proteoglycan from the superficial zone of the cartilage facing the joint cavity. These findings demonstrate that, at least in this model, cartilage proteoglycan loss is not due to the action of proteases present in the synovial fluid. Moreover it suggests that the chondrocytes in the mid-zone of the cartilage are responsive to those signals stimulating proteoglycan breakdown. There was no significant loss of collagen from the cartilage over the time period of this study. The synovial lining from arthritic joints, in contrast, showed a progressive increase in both proteoglycan and collagen.

Increased release of matrix components from articular cartilage in experimental canine osteoarthritis

The release rates of specific components of the proteoglycan aggregates (G1 domain, the chondroitin sulfate and keratan sulfate containing portion of the protein core, and link protein) of the articular cartilage of mature beagles were studied at early stages of canine experimental osteoarthritis (OA), generated by transection of the anterior cruciate ligament. Analysis of cartilage explants and synovial fluids indicates that at early stages of experimental OA, there is increased release of the proteoglycan aggregates of the articular cartilage. This involves a release from the tissue of the components of the proteoglycan that are specifically involved with aggregation together with the glycosaminoglycans of the proteoglycan. These components were detected at elevated levels in the media of explants of cartilage from the operated joint, and in the synovial fluids of the operated joints.

Studies on the quantification of proteoglycans by the dimethylmethylene blue dye-binding method. Specificity, quantitation in synovial lavage fluid, and automation

The dimethylmethylene blue (DMMB) dye-binding technique is widely used for the quantification of sulfated glycosaminoglycans (sGAG) and proteoglycans. We conducted further studies on this technique in our laboratory and found that concentrations of DNA and RNA in excess of 20 micrograms/ml interfered negatively with the detection of sGAGs; interference was eliminated by using DNase and RNase. Hyaluronan at 40 micrograms per ml did not interfere with the detection of sGAG. However, because of the higher concentrations of hyaluronan in synovial lavage fluid, it was necessary to treat this fluid with Streptomyces hyaluronidase in order to quantify sGAG. The DMMB assay was automated with a laboratory work station and compared to the standard method.

Inhibition of interleukin-1-induced synovitis and articular cartilage proteoglycan loss in the rabbit knee by recombinant human interleukin-1 receptor antagonist

Intra-articular injection of interleukin-1 (IL-1) into the knee joints of rabbits produces a synovitis associated with the loss of proteoglycan from the matrix of articular cartilage. This experimental finding supports the hypothesis that IL-1 is a possible mediator of the pathology of inflammatory joint diseases and suggests that antagonism of IL-1 could offer a therapeutic approach to these diseases. It has recently been reported that culture of human monocytes on adherent IgG stimulates these cells to synthesize a specific inhibitor of IL-1 bioactivity (IL-1ra) that acts as a receptor antagonist with lymphocytes and mesenchymal cells. We have now shown that intravenous injection of IL-1ra into rabbits given an intra-articular injection of recombinant IL-1 beta not only inhibits the entry of leukocytes into the synovial lining and joint cavity but blocks the ability of IL-1 to cause loss of proteoglycan from articular cartilage. This ability of IL-1ra to inhibit IL-1-induced arthritis in the rabbit reveals that this protein has appropriate pharmacokinetic and pharmacodynamic properties and further strengthens the belief that it may be a useful therapeutic agent.

In vivo effects of interleukin-1 on articular cartilage. Prolongation of proteoglycan metabolic disturbances in old mice

We investigated the effects of intraarticular injections of interleukin-1 alpha (IL-1 alpha) into the knee joints of young (3-month-old) and old (18-month-old) C57Bl/10 mice. In this in vivo study, 35S-sulfate incorporation and release were used to compare the effects of IL-1 on patellar cartilage proteoglycan metabolism. IL-1-induced stimulation of proteoglycan degradation was confined to the first 24 hours after injection in both young and old animals, and was only slightly lower in old cartilage than in young. In old patellar cartilage, IL-1-induced suppression of proteoglycan synthesis appeared to be more prolonged. Also, the amount of time needed to restore the cartilage matrix, characterized by proteoglycan synthesis above normal levels, was longer in old animals. Histologic analysis confirmed the retarded recovery in the cartilage of old mice. Autoradiography showed that the chondrocytes of the medial side of the femorotibial area were most vulnerable to IL-1-induced suppression of proteoglycan synthesis, especially the medial tibial plateau. As with the patellar cartilage, IL-1-induced suppression of proteoglycan synthesis in this area of articular cartilage was more prolonged in old animals. Our data indicated that the impact of IL-1 on articular cartilage is higher in old mice and that, consistent with certain loci found to be at risk in experimental osteoarthritis, there are sites at which IL-1 is more likely to act.

Proteoglycans of articular cartilage: changes in aging and in joint disease

In human osteoarthritis and animal models of degenerative joint disease, damage to the structure of cartilage proteoglycan is a central event. Loss of proteoglycan from the matrix alters the physicochemical properties of the tissue, but the pathological process and biochemical mechanisms that lead to this loss are poorly understood. This review examines the present state of knowledge regarding proteoglycan structure and the changes that occur in aging and osteoarthritis. It also discusses how these studies will influence the development of new methods for measuring cartilage breakdown.