Cartilage Proteoglycan Synthesis Research Articles

The effect in vitro of irrigating solutions on intact rat articular cartilage

Rat patellae were preincubated with culture medium M199 for one hour and then with either fresh culture medium or Ringer's solution, Ringer lactate, Ringer glucose, normal saline or Betadine for another hour. The rate of proteoglycan synthesis in the articular cartilage was then measured by uptake of 35SO4 for the next 16 hours. Cartilage metabolism was inhibited by all of the solutions even after a recovery time of 16 hours. The inhibition was by 5% for Ringer's solution, 10% for Ringer glucose (p < 0.01), 20% for saline and Ringer lactate (p < 0.001) and 55% for Betadine (p < 0.001). Ringer's solution is therefore the best choice for joint irrigation during arthroscopy or other procedures.

Nitric-Oxide Mediates Suppression of Cartilage Proteoglycan Synthesis by Interleukin-1

Slices of rabbit articular cartilage synthesized large quantities of nitric oxide (NO) following exposure to human recombinant interleukin-1β (hrIL-1β) or rabbit synovial cytokines (CAF). Each of these stimuli also strongly suppressed the biosynthetic incorporation of into the glycosaminoglycans (GAGs) of cartilage proteoglycans. Treatment of cartilage fragments with L-NG-monomethylarginine (L-NMA), a competitive inhibitor of NO synthase, both inhibited NO synthesis in response to IL-1 and CAF and restored proteoglycan synthesis. D-NMA was inactive in this regard, and L-arginine reversed the effects of L-NMA. S-nitrosylacetylpenicillamine (SNAP), an organic donor of NO, reversibly mimicked the effect of IL-1 and CAF on 35SO2−4 incorporation. These data suggest that endogenously synthesized NO is the mediator which reduces cartilage proteoglycan synthesis in response to cytokines such as IL-1 and CAF. Antagonists of NO production may promote cartilage matrix synthesis and thus have potential as chondroprotective or chondroreparative agents.

ARG-Gly-AsP-Ser Peptide Analogs Suppress Cartilage Chondrolytic Activities of Integrin-Binding and Nonbinding Fibronectin Fragments

We have reported that Fn fragments (Fn-f), which have been detected in synovial fluids of osteoarthritis and rheumatoid arthritis patients, can potently cause cartilage chondrolysis and depress proteoglycan (PG) synthesis in cartilage tissue cultured as explants. Amino-terminal 29-kDa, gelatin-binding 50-kDa, and integrin-binding 140-kDa Fn-f are active. In order to investigate the mode of action and devise means of blocking the damage mediated by all Fn-f, we have tested the effects of various analogs resembling the integrin binding sequence, Arg-Gly-Asp-Ser, on blocking Fn-f-mediated chondrolysis. The analog peptides, Gly-Arg-Ala-Asp-Ser-Pro-Lys and Arg-Phe-Asp-Ser, at concentrations as low as 1 μM, blocked the effects of all three Fn-f on cartilage degradation, while the native sequence peptide, Arg-Gly-Asp-Ser, had very low Fn-f-blocking activity and by itself caused cartilage damage. Random sequence peptides dissimilar to the analog sequences were inactive as inhibitors as well as was a sequence analog, Phe-Asp-Arg-Ser, related to the Arg-Phe-Asp-Ser inhibitor. The analog inhibitory peptides decreased rates of Fn-f-mediated PG degradation and release from cartilage and decreased Fn-f-mediated PG synthesis depression. The analog inhibitory peptides alone had no detectable effect on cartilage PG degradation or PG synthesis rates. These data show that the chondrolytic activities of integrin-binding and nonbinding Fn-f can be blocked by synthetic peptide analogs of the Arg-Gly-Asp-Ser sequence and suggest that these peptides may be useful for blocking other activities of Fn-f.

Site-specific cartilage changes in murine degenerative knee joint disease induced by iodoacetate and collagenase.

Degenerative joint disease was induced in the knee joints of mice by intraarticular injection of two different stimuli: iodoacetate and highly purified collagenase. Proteoglycan synthesis was measured in vivo at different time points in four topographical areas of the knee joint (central and peripheral parts of the patella and central parts of the medial and lateral tibial plateaus) and was compared with histological observations of localized damage to the joint. In vitro incubation with iodoacetate had a direct effect on proteoglycan metabolism. Intra-articular injection of iodoacetate in vivo inhibited the proteoglycan synthesis in cartilage from the central part of the patella. In the peripheral part of the patella, inhibition on day 1 was followed by stimulation of synthesis on days 3-30. Proteoglycan synthesis also was inhibited in the central parts of the medial and lateral tibial plateaus. The areas with inhibited synthesis had loss of safranin O staining on histology. In vitro incubation with collagenase did not have a direct effect on the proteoglycan metabolism of intact cartilage; this led to the assumption that osteoarthritis after injection of collagenase is caused by ligamentous injury, which leads to an unstable joint. Injection of collagenase in vivo stimulated the proteoglycan synthesis in cartilage from the central and peripheral parts of the patella. In an early stage of the process, the cartilage from the tibial plateaus also was slightly stimulated.(ABSTRACT TRUNCATED AT 250 WORDS)

Fibronectin Fragments Alter Matrix Protein Synthesis in Cartilage Tissue Cultured in Vitro

We reported earlier that fibronectin fragments (Fn-f) added to bovine articular cartilage cultured in serum-free culture causes marked protease expression with resultant proteoglycan (PG) degradation and release into the culture media. We have further characterized the effects of Fn-f by studies of the effects on proteoglycan, collagen, general protein, and DNA synthesis and reversibility of the cartilage damage. We report here that the most active Fn-f, a 29-kDa amino-terminal Fn-f, when added to a 1 μM concentration, depressed PG and general protein synthesis in cartilage by over 50% within 24 h, as measured by sulfate and methionine/cysteine incorporation, respectively. This same Fn-f decreased PG synthesis throughout the full thickness cartilage section as shown by autoradiography. PG and general protein synthesis were significantly depressed within 24 h by 29-kDa Fn-f concentrations as low as 10 nM. Synthesis rates were effected by 100-fold lower Fn-f concentrations than was induction of proteinases. Removal of the 29-kDa Fn-f allowed a gain to supernormal levels of PG and protein synthesis. Cartilage damaged to the extent of removal of over 50% of the total PG did not replace PG after over 4 weeks in 10% serum - Dulbecco′s modified Eagle minimum with or without added TGF-bl and rIGF-a. These data show that while the effects of Fn-f on elevating protease expression and depressing PG synthesis are reversible, the resultant cartilage damage is apparently irreversible in vitro. Therefore, if Fn-f-mediated cartilage damage occurs as part of cartilage disease processes, the pathologic effects would be quite significant.

Alterations of proteoglycan synthesis in rabbit articular cartilage induced by intra-articular injection of papain

In order to investigate the biochemical alteration of proteoglycan (PG) synthesis during cartilage repair, reversible destruction was induced by injecting papain into the knee joint cavity of rabbits. The PG synthesis in the cartilage was examined using Na2 35SO4 and high performance liquid chromatography (HPLC). PGs labeled with 35SO4(2-) (35S-PGs) were extracted from normal and papain-treated cartilage, and the amount of synthesis, ability to aggregate with hyaluronan (HA), and the composition of glycosaminoglycan and chondroitin sulfate isomer labeled with 35SO4(2-) (35S-GAG and 35S-CS isomer) were analyzed. Synthesis of 35S-PGs, especially those that were unable to aggregate with HA (nonaggregating 35S-PGs), increased in papain-treated cartilage compared with that in normal cartilage. The acceleration and qualitative change in PG synthesis in the papain-treated cartilage are considered to be responses to the supplementation of the loss of cartilage PGs induced by papain. The compositions of 35S-GAG and 35S-CS isomer of the nonaggregating 35S-PGs differed from those of 35S-PGs which were able to aggregate with HA (aggregating 35S-PGs) in the papain-treated cartilage as well as in the normal cartilage. However, the compositions of both nonaggregating and aggregating 35S-PGs in the papain-treated and normal cartilage were similar. These results indicate that most of the nonaggregating 35S-PGs in papain-treated cartilage have properties similar to those in normal cartilage and are not simple degradation products of aggregating 35S-PGs; they also suggest that the supplementary reaction for PG content in the cartilage during its repair process is not simple acceleration in PG turn-over but the enhancement of PG synthesis accompanied by alterations in aggregating ability and the compositions of GAG and CS isomer.

Maintenance of the synthesis of large proteoglycans in anatomically intact murine articular cartilage by steroids and insulin-like growth factor I.

The exact regulation of the synthesis of cartilage specific molecules, such as collagen type II and aggrecan, by articular chondrocytes is unknown, but growth factors and hormones probably play an important part. The effects of glucocorticosteroids (prednisolone and triamcinolone), in combination with insulin-like growth factor I (IGF-I), on the synthesis and hydrodynamic volume of proteoglycans from murine patellar cartilage were investigated. The in vitro effect of IGF-I and steroids on proteoglycan synthesis in murine patellar cartilage was evaluated by [35S]sulphate incorporation in combination with dissociative gel chromatography using a Sephacryl S-1000 column. The impact of in vivo prednisolone (0-5 mg/kg) on proteoglycan synthesis in murine patellar cartilage was analysed by [35S]sulphate incorporation immediately after dissection from the knee joint. Prednisolone stimulated proteoglycan synthesis in murine patellar cartilage from normal knees and in cartilage from knees injected with papain in vitro in the absence and presence of IGF-I. Moreover, oral administration of prednisolone for seven days to C57Bl10 mice resulted in enhanced proteoglycan synthesis in patellar cartilage. The incubation of patellar cartilage for 48 hours without serum or growth factors led to the synthesis of proteoglycans with a smaller hydrodynamic volume than those synthesised immediately after dissection of the patellae. This could either be circumvented by the addition of IGF-I or by the addition of glucocorticosteroids (prednisolone or triamcinolone) to the culture medium. These results show that in a dose range of 0.0003-0.3 mmol/l, glucocorticosteroids, like IGF-I, stimulate proteoglycan synthesis and maintain the synthesis of hydrodynamically large proteoglycans by chondrocytes from murine articular cartilage. This indicates that glucocorticosteroids might play a part in the preservation of matrix integrity in articular cartilage.

Elevated synovial fluid levels of interleukin‐6 and tumor necrosis factor associated with early experimental canine osteoarthritis

To measure levels of cytokines, proteases, and glycosaminoglycans (GAG) in synovial fluid (SF) from the knees of animals with experimental osteoarthritis (OA) and from their contralateral (control) knees, and to compare and correlate these values with each other as well as with measures of proteoglycan synthesis in the corresponding articular cartilage. This study will help to identify cytokines of potential importance in the early stages of the development of OA. OA was induced in 12 mature animals by sectioning the anterior cruciate ligament. After 3 months, SF from the operated and contralateral (control) knee joints was assayed for interleukin-6 (IL-6), tumor necrosis factor (TNF), IL-1, latent metalloproteinase, and sulfated GAG. Proteoglycan synthesis in the corresponding articular cartilage was also measured. IL-6 levels in SF from the operated joint compared with the control joint were significantly elevated in 11 of 12 animals. TNF levels were also elevated in 10 of 11 SF samples from operated joints, but to a lesser extent than those of IL-6. IL-1 and IL-1 inhibitors were undetectable in either the operated or control joint SF. The GAG concentration was elevated in SF from experimental OA joints. This elevation correlated with that of TNF, but not IL-6. There was no significant difference in the concentration of APMA-activatable metalloproteinase. The rate of proteoglycan synthesis was higher in the cartilage from the operated joint in 8 of 12 animals, and the mean rate of synthesis was significantly higher than in the control joint. There was a positive correlation between this increase in cartilage proteoglycan synthesis (operated versus control) and the increase in SF IL-6, but there was no correlation with the levels of TNF or GAG. This is the first study of SF levels of cytokines in early experimental OA. Our results show surprisingly high levels of IL-6 in operated joints, where the cytokine could act directly on the chondrocytes, and thus play a role in mediating their responses to cartilage injury.

Differential modulation of degradative and repair responses of interleukin-1-treated chondrocytes by platelet-derived growth factor

Interleukin 1 (IL-1) plays a dual role in cartilage matrix degeneration by promoting extracellular proteinase action such as the matrix metalloproteinases (increased degradation) and by suppressing the synthesis of extracellular matrix molecules (inhibition of repair). Platelet-derived growth factor (PDGF) is a wound-healing hormone which is released along with IL-1 during the inflammatory response. Since previous studies have shown that PDGF enhances IL-1 alpha effects on metalloproteinase activity, in this report, we have examined whether PDGF modifies IL-1 beta effects on cartilage proteoglycan synthesis. Initially, we confirmed that rabbit articular chondrocytes treated with IL-1 beta + PDGF induced higher proteinase activity, in comparison with IL-1-treated cells. We further observed that the increased proteinase activity correlated with an increase in the synthesis of collagenase/stromelysin proteins and a corresponding increase in the steady-state mRNA levels for both the enzymes. Studies on IL-1 receptor expression suggested that PDGF caused an increase in IL-1 receptor expression which, by augmenting the IL-1 response, may have led to the increase in proteinase induction. Analysis of proteoglycan synthesis confirmed that IL-1 reduced the incorporation of sulphated proteoglycan, aggrecan, into the extracellular matrix of chondrocytes, whereas PDGF stimulated it. However, cells treated with IL-1 + PDGF synthesized normal levels of aggrecan. This is in contrast with cells treated with IL-1 + fibroblast growth factor, in which case only proteinase activity was potentiated. The results allow us to conclude that (a) the two effector functions that play a role in matrix remodelling, namely matrix lysis (proteinase induction) and matrix repair (proteoglycan synthesis), occur via distinct pathways and (b) PDGF may play a crucial role in cartilage repair by initially causing matrix degradation followed by promoting new matrix synthesis.

Independent effects of interleukin 1 on proteoglycan synthesis and proteoglycan breakdown of bovine articular cartilage in vitro.

We studied the effects of human recombinant interleukin-1 beta on proteoglycan metabolism of bovine articular cartilage in organ culture. IL-1 was more potent in inhibiting synthesis (IC50 4 ng/mL) than in stimulating breakdown of proteoglycans (EC50 200 ng/mL). Inhibition of proteoglycan synthesis began to plateau earlier (2 days) than stimulation of proteoglycan release (4 days). Both effects could be neutralized with a polyclonal anti-IL-1 beta antibody; however, higher antibody titers were required to block IL-1 effects on proteoglycan synthesis than to neutralize those on proteoglycan release. Chloroquine, but not hydrocortisone, blocked IL-1-mediated proteoglycan breakdown. Both drugs, however, augmented IL-1-induced inhibition of proteoglycan synthesis. Our data suggest that the effects of IL-1 on articular cartilage proteoglycan synthesis and proteoglycan breakdown can be regulated independently.

Suppression of human cartilage proteoglycan synthesis by rheumatoid synovial fluid mononuclear cells activated with mycobacterial 60-kd heat-shock protein.

To examine whether T cell reactivity toward heat-shock proteins (HSP) contributes to cartilage destruction in rheumatoid arthritis (RA). An in vitro system was used, in which human cartilage explants were cocultured with hsp60-activated synovial fluid mononuclear cells (SFMC) from patients with RA, and proteoglycan (PG) synthesis was measured. The hsp60-activated SFMC suppressed cartilage PG synthesis. This effect was dependent on the production of interleukin-1 (IL-1) and tumor necrosis factor alpha (TNF alpha). Mycobacterial 60-kd heat-shock protein can activate rheumatoid SFMC to suppress human cartilage PG synthesis. This suppression is mediated by IL-1 and TNF alpha.

Articular cartilage explant culture; an appropriate in vitro system to compare osteoarthritic and normal human cartilage.

Proteoglycan metabolism of normal and histologically mild to moderate osteoarthritic cartilage explants were studied. Explants were obtained from the human knee of donors aged over 40 years. Proteoglycan content, synthesis and release were very similar in normal cartilage obtained from donors with focal osteoarthritis and cartilage obtained from donors without any sign of osteoarthritis. This suggests that cartilage obtained from donors with focal osteoarthritis indeed can be considered as "normal". The relatively large surface area-compared to their natural setting in the joint- of cartilage explants in culture did not affect the parameters measured, as there was a strong linear correlation between these parameters and the weight of the explants. From our results, we conclude that the use of full depth cartilage tissue explants is a reliable way to assess and compare proteoglycan content, synthesis and release in normal and osteoarthritic cartilage from the same donor.

Insulin-like growth factor stimulation of articular chondrocyte proteoglycan synthesis. Availability and responses at different ages.

It was found that recovery of articular chondrocyte proteoglycan (PG) synthesis was retarded in old mice after in vivo exposure to both IL-1 or hydrogen peroxide. We examined whether this could be related to diminished serum levels of insulin-like growth factor 1 (IGF-1), the main anabolic factor, or to changes in cartilage IGF responsiveness with age. A small decline of IGF-1 concentration was observed in serum of old mice, but the level still appeared to be supra-optimal to maintain normal cartilage PG synthesis over a culture period of 1 to 3 days. Moreover, PG synthesis was at least equally stimulated in patellar cartilage from 18-month-old mice compared to 3-month-old mice over a wide range of IGF-1 concentrations, and similar findings were obtained after stimulation with serum. In addition, we studied the capacity of IGF-1 or serum to induce recovery of PG synthesis in vitro after IL-1 exposure in vivo. In a 3-day culture period normal cartilage PG synthesis was stimulated to the same extent with serum or IGF-1, but recovery from IL-1 mediated suppression of PG synthesis was more pronounced with serum. This latter capacity was similar for serum of mice aged 3 or 18 months and was noted for both young and old cartilage. Our data show that retarded recovery of chondrocyte PG synthesis in old mice cannot be explained by age-related changes in IGF-1 availability and cartilage responses to IGF. They also indicate that serum factors other than IGF-1 are important for recovery, either alone or in combination with IGF-1.

Antigen-activated T cells inhibit cartilage proteoglycan synthesis independently of T-cell proliferation.

Previously we have shown that blood mononuclear cells (MNC) obtained from patients with rheumatoid arthritis (RA) have the capacity to induce depletion of proteoglycans (PG) in human cartilage explants. This was observed especially after stimulating MNC with mycobacterial antigens, rather than with the mitogen Concanavalin A (Con A). We have now co-cultured cartilage explants in the presence of T-cell clone A2b obtained from the rat model of adjuvant arthritis (AA). We show that inhibition of the cartilage PG synthesis is a consequence of antigen-specific T-cell activation and that it is mediated by a humoral factor. This seems to be a cytokine rather than an enzyme. Moreover, at the level of polyclonally responding T cells, inhibition of PG synthesis due to T-cell activation by mycobacterial antigens was shown to depend on prior mycobacterial immunization. Arthritogenic T-cell clone A2b also showed PG synthesis inhibitory effects when co-cultured with cartilage alone. The inhibitory activity was shown to be unrelated to the degree of T-cell proliferation. We conclude that antigen-specific T-cell activation may be one of the initiating events leading to cartilage damage in arthritic processes. The measurement of T-cell-mediated PG synthesis inhibition may be a more sensitive and relevant assay for the detection of pathogenic T cells than T-cell proliferation.

Platelet-activating factor inhibits proteoglycan synthesis and enhances neutrophil-mediated proteoglycan degradation in cartilage explants.

Platelet-activating factor (PAF), which stimulates the release of tissue-destructive enzymes and reactive oxygen metabolites from neutrophils, was investigated for its role in neutrophil-mediated cartilage breakdown. Bovine cartilage explants were incubated with or without human neutrophils, PAF, and other reagents. Cartilage damage was measured as either proteoglycan degradation (percent release of 35S-labeled proteoglycan from 35S-labeled cartilage) or inhibition of proteoglycan synthesis (rate of incorporation of 35S into proteoglycan). PAF increased neutrophil-mediated proteoglycan degradation in the 2-20 microM range. Three specific PAF-receptor antagonists, WEB2086, CV3988, and CV6209, reversed this effect of PAF. These antagonists also reduced the enhancement of neutrophil-mediated cartilage damage caused by granulocyte-macrophage colony-stimulating factor (GM-CSF) and tumor necrosis factor alpha (TNF alpha). The results suggest that there may be a positive feedback mechanism whereby cytokine-primed neutrophils produce PAF, which amplifies the release of other tissue-damaging substances from neutrophils. In the absence of neutrophils, PAF (2-20 microM) inhibited the synthesis of proteoglycan by bovine cartilage. Neutrophils also inhibit proteoglycan synthesis, but PAF probably is not involved in this effect of neutrophils because the PAF receptor antagonists had no consistent effect. PAF increases neutrophil-mediated cartilage proteoglycan degradation in vitro. GM-CSF and TNF alpha enhancement of neutrophil damage to cartilage is partly due to PAF. PAF alone inhibits cartilage proteoglycan synthesis.

Inhibition of proteoglycan synthesis by transforming growth factor beta in anatomically intact articular cartilage of murine patellae.

The effect of transforming growth factor beta (TGF beta) on proteoglycan synthesis and degradation in anatomically intact articular cartilage of murine patellae was studied. Exogenously added TGF beta up to a concentration of 200 pmol/l had no effect on proteoglycan synthesis in intact articular cartilage. Neutralisation of endogenously produced TGF beta with a specific monoclonal antibody to TGF beta, however, led to stimulation of proteoglycan synthesis, indicating that TGF beta itself inhibits proteoglycan synthesis in anatomically intact cartilage. Transforming growth factor beta decreased the degradation of proteoglycans in intact cartilage in the absence of fetal calf serum or insulin-like growth factor 1. In the presence of fetal calf serum or insulin-like growth factor 1, TGF beta had no additional effect on proteoglycan breakdown.

Oxidation of articular cartilage glyceraldehyde-3-phosphate dehydrogenase (G3PDH) occurs in vivo during carrageenin-induced arthritis

Articular cartilage proteoglycan biosynthesis was substantially inhibited by the competitive glycolytic inhibitor 2-deoxyglucose (approximately 65% at 100 mM), but to a much lesser degree (approximately 10%) by the oxidative phosphorylation uncoupler, 2,4-dinitrophenol. These results confirm that articular cartilage proteoglycan synthesis mostly utilises ATP which is generated by glycolysis. In addition, we have utilised the loss of the relatively specific labelling of glyceraldehyde-3-phosphate dehydrogenase (G3PDH) by [3H]-iodoacetic acid to show that rabbit articular G3PDH is oxidised in vivo during the animal model of acute arthritis, carrageenin-induced arthritis, in the same way as we have previously shown that cartilage G3PDH is oxidised after in vitro exposure to sublethal doses of H2O2. The oxidation of rabbit G3PDH in vivo (18 hr post-injection) corresponds with the maximal influx of PMNL cells into the arthritic synovial fluid and with substantial inhibition of proteoglycan core protein synthesis. We propose that H2O2 released from "activated" PMNLs and macrophages is responsible for the "down-regulation" of biosynthetic processes found in cartilage during acute inflammation.

Effects of Tiaprofenic Acid on the Concentration and Metabolism of Proteoglycans in Normal and Degenerating Canine Articular Cartilage

The effects of tiaprofenic acid (TPA), a nonsteroidal antiinflammatory drug with high potency as a cyclooxygenase inhibitor, on the metabolism of normal and degenerating articular cartilage were examined. When present in the culture medium in clinically relevant concentrations encompassing those achieved in synovial fluid of patients treated with the drug, TPA had no significant effects on net proteoglycan synthesis in organ cultures of normal, osteoarthritic or atrophic canine articular cartilage. When fed to dogs for 8 weeks in a daily dose of 100 mg, TPA had no apparent effect on cartilage water content or uronic acid concentration. The suppression of net cartilage proteoglycan synthesis caused by immobilization was not affected by administration of TPA nor did the drug affect the proportion of newly synthesized glycosaminoglycans recovered from the spent culture medium, suggesting that it did not increase proteoglycan catabolism or affect the integrity of the cartilage matrix.

Protective effect of rimexolone on cartilage damage in arthritic mice: A comparative study with triamcinolone hexacetonide

We studied the effect of the local steroid preparation rimexolone on cartilage metabolism in arthritis and normal joints. Prolonged anti-inflammatory action was evident after intraarticular injection of a single dose of 450 micrograms into mice with monoarticular antigen-induced arthritis. Suppression of inflammation lasted for at least 21 days. A single dose of 25 micrograms of the anti-inflammatory steroid triamcinolone hexacetonide (THA) induced comparable suppression in the initial stage of the arthritis, but the suppressive action was of shorter duration. Both drugs significantly prevented osteophyte formation, which is a characteristic feature of this type of experimental arthritis. Although chondrocyte proteoglycan (PG) synthesis in patellar cartilage was significantly suppressed upon injection in normal joints, both steroids counteracted the severe suppression of PG synthesis in arthritic joints. These data indicate that although steroids may have significant side effects on chondrocytes, the overall effect on arthritic chondrocytes is beneficial. An advantage of rimexolone over THA is its prolonged retention, which may explain its sustained anti-inflammatory action, and the lack of systemic effects.

CAMP-dependent protein kinase in chondrocyte cultures: Holoenzyme activation, phosphorylation of cellular proteins, effects of NSAIDs and possible role in proteoglycan synthesis

R ECENT EVIDENCE showed that chondrocytes treated in culture with nonsteroidal antiinflammatory drugs (NSAIDs) exhibited reduced eicosanoid production, which was coupled to reduced intracellular accumulation of cyclic adenosine monophosphate (CAMP).’ Typically, NSAIDs have variable effects on cartilage proteoglycan and collagen synthesis and catabolism.2*3 Some NSAIDs are known to stimulate proteoglycan synthesis. These include sulindac sulfide4 and benoxaprofen5 However, the majority, including fenoprofen4 ibuprofen4 indomethacin,2T6*7 phenylbutazone,8 salicylates,7~9~‘0 and tolmetin,” suppress proteoglycan synthesis. Piroxicam may enhance proteolycan synthesisI or be without effect 12,13 the same can be said of the effect of tiaprdfenic acid2 and in some cases, indomethatin and sulindac sulfoxide.4 Many of these results come from studies conducted on articular cartilage explant culturesI or on cultured chondrocytes’2q’3 where a concentration range of NSAIDs can be tested readily. A recent review has appeared on this subject.” Two types of CAMP-dependent protein kinase (cAMPPk), type 1 and type 2, resolved by differential elution from diethylaminoethylcellulose (DEAE-cellulose), have been shown to