Oncostatin M (OSM) stimulates resorption and inhibits synthesis of proteoglycan in porcine articular cartilage explants

Identification of polymorphic loci in OSMR and GHR genes and analysis of their association with growth traits in sheep

The aim of this study was to analyze the effect of OSMR and GHR genes polymorphisms on growth traits in sheep. The single nucleotide polymorphisms of sheep OSMR and GHR genes were identified by DNA sequencing technology. A total of two intronic mutations g.2443 T > C and g.170196 A > G were identified in OSMR and GHR, respectively. Correlation analysis was carried out between the obtained genotypes and the growth traits of sheep. The results showed that at the OSMR g.2443 T > C locus, the body weight, chest circumference and cannon circumference of the TT genotype sheep were significantly higher than those of the CC genotype sheep (p < .05). At the GHR g.170196 A > G locus, the body weight, body length, chest circumference and cannon circumference of the AA genotype sheep were significantly higher than those of the AG genotype and GG genotype sheep (p < .05). Moreover, the body weight of sheep of combination TTOSMR/AAGHR genotype was significantly higher than that of other combination genotypes (p < .05). Therefore, we believe that the polymorphic sites identified in the OSMR and GHR genes can be used as candidate molecular markers for breeding good traits in sheep.

Multifaceted oncostatin M: novel roles and therapeutic potential of the oncostatin M signaling in rheumatoid arthritis

Rheumatoid arthritis (RA) is a self-immune inflammatory disease characterized by joint damage. A series of cytokines are involved in the development of RA. Oncostatin M (OSM) is a pleiotropic cytokine that primarily activates the Janus kinase (JAK)/signal transducer and activator of transcription (STAT) signaling pathway, the mitogen-activated protein kinase (MAPK) signaling pathway, and other physiological processes such as cell proliferation, inflammatory response, immune response, and hematopoiesis through its receptor complex. In this review, we first describe the characteristics of OSM and its receptor, and the biological functions of OSM signaling. Subsequently, we discuss the possible roles of OSM in the development of RA from clinical and basic research perspectives. Finally, we summarize the progress of clinical studies targeting OSM for the treatment of RA. This review provides researchers with a systematic understanding of the role of OSM signaling in RA, which can guide the development of drugs targeting OSM for the treatment of RA.

Conditioned serum in vitro treatment of chondrocyte pellets and osteoarthritic explants

BACKGROUND

Autologous conditioned serum (ACS) is used to treat osteoarthritis in horses, although its effects are not fully investigated.

OBJECTIVES

To investigate the effects of equine serum and conditioned serum on chondrocytes stimulated with interleukin (IL)-1β and cartilage explants with mild osteoarthritis.

STUDY DESIGN

In vitro experimental study.

METHODS

The effect of three different serum preparations (unincubated control [PS], serum incubated 24 h [PS24h] and serum incubated 24 h in ACS containers [PCS]) pooled from lame horses were tested in two in vitro models. IL-1β and IL-1 receptor antagonist (IL-1Ra) concentrations were measured in all sera. In model 1, chondrocyte pellet cultures were stimulated with IL-1β prior to treatment with the serum preparations for 2 and 48 h. Microarray, polymerase chain reaction, and matrix metallopeptidase-13 analyses were performed. In model 2, cartilage explants from horses with structural osteoarthritis were treated with PS or PCS on days 0, 6 and 12, or left untreated, and evaluated at day 24 using the OARSI grading scale for histological evaluation of articular cartilage.

RESULTS

The IL-1Ra concentration in PS24h and PCS was significantly higher than in PS. In model 1, inflammation- and cartilage matrix degradation-related genes were upregulated after 48 h in all treatment groups versus untreated controls. Cartilage matrix molecules, aggrecan and collagens, were downregulated in PS24h- and PCS-treated pellets versus untreated controls. Growth factor signalling genes were upregulated-FGF7 in all treatment groups, BMP2 in PS24h-, and INHBA in PCS-treated-compared with untreated controls. In model 2, the OARSI score at day 24 was not significantly different between treatment groups.

MAIN LIMITATIONS

Results from in vitro models cannot be directly translated to in vivo situations.

CONCLUSIONS

In vitro treatment with conditioned serum did not alleviate IL-1β-induced responses in chondrocyte pellets or lead to morphological improvement in osteoarthritic cartilage explants.

Oncostatin M: Risks and Benefits of a Novel Therapeutic Target for Atherosclerosis

BACKGROUND

Cardiovascular disease (CVD) is a leading cause of death worldwide. It is predicted that approximately 23.6 million people will die from CVDs annually by 2030. Therefore, there is a great need for an effective therapeutic approach to combat this disease. The European Cardiovascular Target Discovery (CarTarDis) consortium identified Oncostatin M (OSM) as a potential therapeutic target for atherosclerosis. The benefits of modulating OSM - an interleukin (IL)-6 family cytokine - have since been studied for multiple indications. However, as decades of high attrition rates have stressed, the success of a drug target is determined by the fine balance between benefits and the risk of adverse events. Safety issues should therefore not be overlooked.

OBJECTIVE

In this review, a risk/benefit analysis is performed on OSM inhibition in the context of atherosclerosis treatment. First, OSM signaling characteristics and its role in atherosclerosis are described. Next, an overview of in vitro, in vivo, and clinical findings relating to both the benefits and risks of modulating OSM in major organ systems is provided. Based on OSM's biological function and expression profile as well as drug intervention studies, safety concerns of inhibiting this target have been identified, assessed, and ranked for the target population.

CONCLUSION

While OSM may be of therapeutic value in atherosclerosis, drug development should also focus on de-risking the herein identified major safety concerns: tissue remodeling, angiogenesis, bleeding, anemia, and NMDA- and glutamate-induced neurotoxicity. Close monitoring and/or exclusion of patients with various comorbidities may be required for optimal therapeutic benefit.

Time-dependent proteomic and genomic alterations in Toll-like receptor-4-activated human chondrocytes: increased expression of lamin A/C and annexins

Activation of Toll-like receptor-4 (TLR-4) in articular chondrocytes increases the catabolic compartment and leads to matrix degradation during the development of osteoarthritis. In this study, we determined the proteomic and genomic alterations in human chondrocytes during lipopolysaccharide (LPS)-induced inflammation to elucidate the underlying mechanisms and consequences of TLR-4 activation. Human chondrocytes were cultured with LPS for 12, 24, and 36 h to induce TLR-4 activation. The TLR-4-induced inflammatory response was confirmed by real-time PCR analysis of increased interleukin-1 beta (IL-1β), interleukin-6 (IL-6), and tumor necrosis factor alpha (TNF-α) expression levels. In TLR-4-activated chondrocytes, proteomic changes were determined by two-dimensional electrophoresis and matrix-assisted laser desorption/ionization-mass spectroscopy analysis, and genomic changes were determined by microarray and gene ontology analyses. Proteomics analysis identified 26 proteins with significantly altered expression levels; these proteins were related to the cytoskeleton and oxidative stress responses. Gene ontology analysis indicated that LPS treatment altered specific functional pathways including ‘chemotaxis’, ‘hematopoietic organ development’, ‘positive regulation of cell proliferation’, and ‘regulation of cytokine biosynthetic process’. Nine of the 26 identified proteins displayed the same increased expression patterns in both proteomics and genomics analyses. Western blot analysis confirmed the LPS-induced increases in expression levels of lamin A/C and annexins 4/5/6. In conclusion, this study identified the time-dependent genomic, proteomic, and functional pathway alterations that occur in chondrocytes during LPS-induced TLR-4 activation. These results provide valuable new insights into the underlying mechanisms that control the development and progression of osteoarthritis.

Predictors of primary Achilles tendon ruptures

BACKGROUND

The Achilles tendon is the strongest tendon in the human body. The incidence of Achilles tendon ruptures appears to be increasing.

OBJECTIVES

The aim of this review was to systematically summarize predictors influencing Achilles tendon rupture (ATR) risk.

METHODS

A systematic literature search was performed of reported determinants influencing the ATR risk. Studies were eligible if there was: (i) description of determinants predicting ATR; (ii) an outcome defined as ATR; (iii) any study design with at least ten adults included with ATR; (iv) use of statistical tests regarding differences between patients with an ATR and healthy controls; (v) a full text article available; (vi) an article written in English, German or Dutch. Quality assessment was done using a standardized criteria set. Best-evidence synthesis was performed.

RESULTS

We included 31 studies, of which two (6.5%) were considered high-quality studies. Moderate evidence was found for increased ATR risk and decreased fibril size of Achilles tendon.

CONCLUSION

Based on the results of this systematic review there is moderate evidence that decreased tendon fibril size increases the ATR risk. There is limited evidence for many other factors, some of which are modifiable, such as increased body weight, oral corticosteroid use and quinolone use and living in an urban area, and therefore may be of interest in future studies. Furthermore, these results showed that more high-quality studies are needed for evaluating the determinants influencing the ATR risk.

Oncostatin M binds to extracellular matrix in a bioactive conformation: implications for inflammation and metastasis

Oncostatin M (OSM) is an interleukin-6-like inflammatory cytokine reported to play a role in a number of pathological processes including cancer. Full-length OSM is expressed as a 26 kDa protein that can be proteolytically processed into 24 kDa and 22 kDa forms via removal of C-terminal peptides. In this study, we examined both the ability of OSM to bind to the extracellular matrix (ECM) and the activity of immobilized OSM on human breast carcinoma cells. OSM was observed to bind to ECM proteins collagen types I and XI, laminin, and fibronectin in a pH-dependent fashion, suggesting a role for electrostatic bonds that involves charged amino acids of both the ECM and OSM. The C-terminal extensions of 24 kDa and 26 kDa OSM, which contains six and thirteen basic amino acids, respectively, enhanced electrostatic binding to ECM at pH 6.5-7.5 when compared to 22 kDa OSM. The highest levels of OSM binding to ECM, though, were observed at acidic pH 5.5, where all forms of OSM bound to ECM proteins to a similar extent. This indicates additional electrostatic binding properties independent of the OSM C-terminal extensions. The reducing agent dithiothreitol also inhibited the binding of OSM to ECM suggesting a role for disulfide bonds in OSM immobilization. OSM immobilized to ECM was protected from cleavage by tumor-associated proteases and maintained activity following incubation at acidic pH for extended periods of time. Importantly, immobilized OSM remained biologically active and was able to induce and sustain the phosphorylation of STAT3 in T47D and ZR-75-1 human breast cancer cells over prolonged periods, as well as increase levels of STAT1 and STAT3 protein expression. Immobilized OSM also induced epithelial-mesenchymal transition-associated morphological changes in T47D cells. Taken together, these data indicate that OSM binds to ECM in a bioactive state that may have important implications for the development of chronic inflammation and tumor metastasis.

Interleukin-6 is elevated in synovial fluid of patients with focal cartilage defects and stimulates cartilage matrix production in an in vitro regeneration model

Introduction

This study aimed to determine whether, as in osteoarthritis, increased levels of interleukin-6 (IL-6) are present in the synovial fluid of patients with symptomatic cartilage defects and whether this IL-6 affects cartilage regeneration as well as the cartilage in the degenerated knee.

Methods

IL-6 concentrations were determined by ELISA in synovial fluid and in conditioned media of chondrocytes regenerating cartilage. Chondrocytes were obtained from donors with symptomatic cartilage defects, healthy and osteoarthritic donors. The effect of IL-6 on cartilage regeneration and on metabolism of the resident cartilage in the knee was studied by both inhibition of endogenous IL-6 and addition of IL-6, in a regeneration model and in osteoarthritic explants in the presence of synovial fluid, respectively. Readout parameters were DNA and glycosaminoglycan (GAG) content and release. Differences between controls and IL-6 blocked or supplemented samples were determined by univariate analysis of variance using a randomized block design.

Results

Synovial fluid of patients with symptomatic cartilage defects contained more IL-6 than synovial fluid of healthy donors (P = 0.001) and did not differ from osteoarthritic donors. IL-6 production of osteoarthritic chondrocytes during cartilage regeneration was higher than that of healthy and defect chondrocytes (P < 0.001). Adding IL-6 increased GAG production by healthy chondrocytes and decreased GAG release by osteoarthritic chondrocytes (P < 0.05). Inhibition of IL-6 present in osteoarthritic synovial fluid showed a trend towards decreased GAG content of the explants (P = 0.06).

Conclusions

Our results support a modest anabolic role for IL-6 in cartilage matrix production. Targeting multiple cytokines, including IL-6, may be effective in improving cartilage repair in symptomatic cartilage defects and osteoarthritis.

K/B×N serum transfer arthritis is delayed and less severe in leukaemia inhibitory factor (LIF)-deficient mice

This study is investigating the role of leukaemia inhibitory factor (LIF) in the development of inflammation and joint damage in the mouse K/B×N serum transfer arthritis model. LIF knock-out (LIF(-/-)) mice were generated by mating heterozygote females (LIF(+/-)) with heterozygote males. Arthritis was induced in 8-20-week-old LIF knock-out mice (LIF(-/-)) by intraperitoneal injection of pooled K/B×N sera (50 µl) on days 0 and 2. Clinical disease was scored daily for 6 days. Safranin-O and haematoxylin-stained sections were scored for synovitis, joint space exudate, cartilage degradation and bone damage. RNA was extracted from ankle joints and used to investigate gene expression levels of tumour necrosis factor (TNF)-α, interleukin (IL)-1, LIF, LIF receptor, oncostatin M (OSM), OSM receptor, IL-6 and their common receptor subunit gp130 by quantitative reverse transcription-polymerase chain reaction (qRT-PCR). The results show that wild-type mice developed severe clinically overt polyarthritis. In contrast, LIF(-/-) mice showed a more than 50% reduction in clinical arthritis severity. Significantly lower histological scores were observed in LIF(-/-) mice compared to wild-type disease controls. LIF(-/-) mice had histopathological scores that were similar to normal healthy mice. IL-6 subfamily cytokine and receptor subunit expression remained unchanged. The expression levels for IL-6 were reduced significantly in all the diseased mice, whether wild-type or LIF(-/-) mice (P < 0·001), compared to healthy wild-type mice. We conclude that LIF contributes to the development of disease in the K/B×N serum transfer model of arthritis. These results provide further evidence for the role of LIF in inflammation and cartilage bone resorption and provide impetus to test the effects of LIF blockade as a therapeutic strategy in rheumatoid arthritis.

Increased expression of IL-6 family members in tendon pathology

OBJECTIVES

Histological examination of pathological tendon generally does not reveal signs of inflammation. However, the inflammatory cytokine IL-6 has been shown to be expressed in ruptured rotator cuff tendon. The aim of this study was to investigate the expression of IL-6 family members in painful posterior tibialis tendon (PTT) and in painful and ruptured Achilles tendon (AT) compared with normal tendon.

METHODS

AT samples were obtained from cadavers (normal) or from patients undergoing surgical procedures to treat chronic painful tendinopathy or ruptured tendon. PTT samples were obtained from patients undergoing surgery for other reasons (normal) and from patients with PTT dysfunction (painful). Total RNA was extracted and mRNA expression was analysed by quantitative real-time PCR.

RESULTS

Collagen type I α-chain I (COL1A1) expression was increased in both painful PTT and AT compared with normal. Ciliary neurotrophic factor levels were increased in painful PTT only. In the painful AT, cyclooxygenase-2 (COX2) and IL-6 expression increased compared with normal. In the ruptured AT, levels of VEGF A, COX2, oncostatin-M, leukaemia inhibitory factor and IL-6 expression were higher compared with both normal and painful AT. IL-6R expression decreased in both painful and ruptured AT compared with normal.

CONCLUSION

Painful AT and PTT show different expression patterns, indicating a substantial difference between those two tendinopathies. Inflammatory markers are up-regulated in painful and particularly in ruptured AT, pointing towards a role of inflammation not only in rupture healing, but also in Achilles tendinopathy.

Development of an in vitro model of feline cartilage degradation

Osteoarthritis is the most common arthropathy of mammalian species including cats. Cartilage degradation is central to the disorder and here we present, for the first time, an in vitro model of feline cartilage degradation which will be useful for further studies in this target species. Feline articular cartilage explant cultures were maintained for 28 days and in the presence of oncostatin M with and without interleukin (IL)-17, tumour necrosis factor (TNF), IL-1alpha, or IL-1beta. Media samples and digested cartilage explants were analysed for glycosaminoglycan (GAG) and collagen content. The combination of IL-1beta and OSM, both at 20 ng/ml, was able to promote GAG release to the greatest extent at 14 days. At 28 days, all groups showed relatively high release of GAG. At 14 days, only IL-1beta and OSM in combination were associated with a statistically significant increase in collagen release over and above control tissue. IL-1beta dose-response studies showed that an IL-1beta dose of 10 ng/ml promotes a statistically significant increase in GAG breakdown when used with OSM, and higher doses of IL-1beta did not result in significantly greater response. The model demonstrated both GAG and collagen degradation and will be of use for further understanding of feline cartilage metabolism and for screening of potential structure-modifying agents to be used in cats.

The effects of p-hydroxycinnamaldehyde from Alpinia galanga extracts on human chondrocytes

Osteoarthritis (OA) is the most common form of arthritis and affects millions of people worldwide. Patients have traditionally been treated with non-steroidal anti-inflammatory drugs (NSAIDs), but these are associated with significant side effects. Purification of the acetone extract of Alpinia galanga afforded p-hydroxycinnamaldehyde, as identified by nuclear magnetic resonance and mass spectrometry analyses. By exploiting the cartilage explant culture, p-hydroxycinnamaldehyde suppressed loss of uronic acid, resulting in release of hyaluronan (HA), sulfated glycosaminoglycans (s-GAGs) and matrix metalloproteinases (MMPs). p-Hydroxycinnamaldehyde and interleukin-1beta (IL-1beta), when incubated in primary human chondrocytes, also reduced release of HA, s-GAG and MMP-2. The results demonstrated: (a) that expression levels of the catabolic genes MMP-3 and MMP-13 were suppressed and (b) mRNA expression levels of anabolic genes of collagen II, SOX9 and aggrecan were increased. This study shows that p-hydroxycinnaldehyde from A. galanga Linn. is a potential therapeutic agent for treatment of OA.

Characterization of an ADAMTS-5-mediated cleavage site in aggrecan in OSM-stimulated bovine cartilage

OBJECTIVE

In a previous study, we identified a 50-kDa G3-containing aggrecan degradation product in bovine cartilage, released from the tissue after interleukin-1 (IL-1) stimulation in the presence of oncostatin M (OSM). Our objective was to purify, determine the N-terminal sequence of this fragment and verify whether this cleavage could be attributed to a disintegrin and metalloproteinase with thrombospondin motifs (ADAMTS)-4 and ADAMTS-5 action in vitro.

METHODS

Collected media from bovine cartilage explant cultures stimulated with IL-1+OSM were subjected to anion-exchange chromatography. The N-terminal sequence of the fragment of interest in the purified fractions was determined by automated Edman sequencing. Fetal bovine aggrecan was digested with full-length recombinant ADAMTS-4 and ADAMTS-5 and resulting degradation products were analyzed by sodium dodecyl sulfate/polyacrylamide gel electrophoresis (SDS/PAGE) and immunoblotting using an anti-G3 antiserum and an anti-neoepitope antibody that had been generated to the new N-terminus of the G3 fragment.

RESULTS

Characterization of the 50-kDa fragment showed that it possesses chondroitin sulfate (CS) and is the result of a cleavage within the C-terminal portion of the CS-2 domain, adjacent to the G3 region. Sequence analysis identified the cleavage region as TQRPAE(2047)-(2048)ARLEIE, suggesting an aggrecanase-derived product. Using an anti-neoepitope antibody specific for the additional cleavage site, it was shown that the product is generated in vitro upon digestion of aggrecan by ADAMTS-5 and, to a much lesser extent, by ADAMTS-4.

CONCLUSIONS

The abundance and rapid rate of release of this degradation product in organ cultures in the presence of OSM suggest that it could result from a unique aggrecan proteolysis mediated by aggrecanases.

Mechanism of proteoglycan aggregate degradation in cartilage stimulated with oncostatin M

OBJECTIVE

To investigate the potential synergistic and differential effects of cytokine combinations on proteoglycan aggregate catabolism in cartilage.

METHODS

Bovine articular cartilage explants were maintained in organ culture and subjected to stimulation with cytokine combinations including interleukin-1alpha (IL-1alpha), IL-1beta, IL-6, IL-17, tumor necrosis factor-alpha (TNFalpha) and oncostatin M (OSM). Aggrecan, link protein and hyaluronan (HA) release and degradation were analyzed, and the effect of the hyaluronidase inhibitor apigenin was investigated.

RESULTS

For all cytokine mixtures studied cleavage of aggrecan only by aggrecanase action was apparent. However, OSM acting synergistically with IL-1 or TNFalpha produced a rapid release of all proteoglycan aggregate components due to both aggrecan and HA degradation. This was abolished by the hyaluronidase inhibitor, apigenin. In addition, in the presence of OSM a low molecular weight aggrecan G3 product was observed, suggesting altered aggrecanase cleavage activity is induced by this cytokine.

CONCLUSIONS

Under cytokine stimulation, aggrecan release from cartilage may take place via proteolysis of the aggrecan core protein or via depolymerization of HA, with the latter mechanism being induced by OSM. OSM is associated with joint inflammation and its participation may account for the more rapid loss of aggrecan from articular cartilage in the inflammatory arthritides, compared to osteoarthritis.

In VitroEvaluation of Leukemia Inhibitory Factor Receptor Antagonists as Candidate Therapeutics for Inflammatory Arthritis

Leukemia inhibitory factor (LIF) and oncostatin M (OSM) are found in appreciable concentrations in synovial fluid from patients with rheumatoid arthritis (RA) but not osteoarthritis. Accordingly, both are potential therapeutic targets in inflammatory diseases of the joints. Several LIF antagonists have been developed. They have the capacity to inhibit the biologic activities of not only LIF but also other interleukin-6 (IL-6) subfamily cytokines, including OSM. Both LIF and OSM share the same receptor, which is part of a cytokine receptor super family in which the glycoprotein 130 (gp130) subunit is a common constituent. The aim of this study was to evaluate the antagonistic potentials of two LIF mutants, LIF05 and MH35-BD. Both are mutant forms of human LIF with reduced affinity for gp130 and greater LIF receptor (LIFR) binding affinity. The results, using Ba/F3 cell proliferation assay, acute-phase protein (haptoglobin) induction analysis in HepG2 human hepatoma cells, a porcine cartilage glycosaminoglycan release assessment for proteoglycan degradation, and a collagen release assay, show that these antagonists inhibit relevant LIF, OSM, and other IL-6 subfamily cytokines in vitro albeit with differential potencies and have, therefore, therapeutic potential for treatment of RA and perhaps other diseases.

Oncostatin M-Induced IL-6 Expression in Murine Fibroblasts Requires the Activation of Protein Kinase Cδ

Oncostatin M (OSM) is an IL-6/LIF cytokine family member whose role has been identified in a range of biological activities in vitro, including up-regulation of inflammatory gene expression and regulation of connective tissue metabolism. However, the mechanisms through which OSM regulates cellular responses are not completely understood. In this study, we show that activation of the calcium-independent or novel protein kinase C (PKC) isoform PKCdelta is a critical event during OSM-mediated up-regulation of IL-6 expression in murine fibroblasts. The pan-PKC inhibitor GF109203X (bisindolylmaleimide I) reduced secretion of IL-6; however, use of Go6976, an inhibitor of calcium-dependent PKC enzymes, did not. The PKCdelta-selective inhibitory compound rottlerin abrogated expression of IL-6 transcript and protein, but only reduced PKCdelta activity when used at higher concentrations as determined by kinase activity assay, suggesting rottlerin may inhibit IL-6 expression in a PKCdelta-independent manner. However, silencing of PKCdelta protein expression, but not the related novel isoform PKCepsilon, by use of RNA interference (i.e., small interfering RNA) demonstrated that PKCdelta is required for murine OSM (mOSM) induction of IL-6 protein secretion. Furthermore, inhibition of PI3K by use of LY294002 reduces expression of IL-6 at both the mRNA and protein level in murine fibroblasts, and we suggest that PI3K is required for activation of PKCdelta. Knockdown of phosphoinositide-dependent kinases PDK-1 or Akt1 using small interfering RNA strategies did not influence mOSM-induced IL-6 expression, suggesting mOSM uses a PI3K-PKCdelta pathway of activation independent of these kinases. Our findings illustrate a novel signaling network used by mOSM that may be important for its mediation of inflammatory processes.

MMP-3 expression and release by rheumatoid arthritis fibroblast-like synoviocytes induced with a bacterial ligand of integrin alpha5beta1

Fibroblast-like synoviocytes (FLSs) play a major role in the pathogenesis of rheumatoid arthritis (RA) by secreting effector molecules that promote inflammation and joint destruction. How these cells become and remain activated is still elusive. Both genetic and environmental factors probably play a role in transforming FLSs into inflammatory matrix-degrading cells. As bacterial products have been detected in the joint and shown to trigger joint inflammation, this study was undertaken to investigate whether a bacterial ligand of integrin alpha5beta1, protein I/II, could contribute to the aggressive behavior of RA FLSs. Protein I/II is a pathogen-associated molecular pattern (PAMP) isolated from oral streptococci that have been identified in the joints of RA patients. The response of RA and osteoarthritis FLSs to protein I/II was analyzed using human cancer cDNA expression arrays. RT-PCR and pro-MMP-3 (pro-matrix metalloproteinase) assays were then performed to confirm the up-regulation of gene expression. Protein I/II modulated about 6% of all profiled genes. Three of these, those encoding IL-6, leukemia inhibitory factor, and MMP-3, showed a high expression level in all RA FLSs tested, whereas the expression of genes encoding other members of the cytokine or MMP-family was not affected. Furthermore, the up-regulation of MMP-3 gene expression was followed by an increase of pro-MMP-3 release. The expression of interferon regulatory factor 1 and fibroblast growth factor-5 was also up-regulated, although the expression levels were lower. Only one gene, that for insulin-like growth factor binding protein-4, was down-regulated in all RA FLSs. In contrast, in osteoarthritis FLSs only one gene, that for IL-6, was modulated. These results suggest that a bacterial ligand of integrin alpha5beta1 may contribute to the aggressive behavior of RA FLSs by inducing the release of pro-inflammatory cytokines and a cartilage-degrading enzyme, such as IL-6 and MMP-3, respectively.

MEK/ERK and signal transducer and activator of transcription signaling pathways modulate oncostatin M-stimulated CCL2 expression in human osteoblasts through a common transcription factor

OBJECTIVE

To analyze the effects of oncostatin M (OSM), a gp130-type cytokine, on CCL2 expression in MG-63 cells, a human osteosarcoma cell line with a characteristic osteoblastic phenotype, and to investigate the signaling pathway involved.

METHODS

The expression of messenger RNA (mRNA) for CCL2 and c-Fos was analyzed by Northern blotting. Amounts of CCL2 released into the supernatant were measured by enzyme-linked immunosorbent assay. Western blotting was used to examine the activation of MAPK signaling pathways. Interactions between activator protein 1 (AP-1) and DNA were evaluated by electrophoretic mobility shift assay.

RESULTS

OSM stimulated CCL2 expression at both the mRNA and the protein levels. Cyclooxygenase 2 (COX-2) was also induced by OSM. However, the up-regulation of CCL2 mRNA was COX-2-independent but required tyrosine kinase and protein kinase C (PKC). OSM stimulated the phosphorylation of MEK-1/2 and ERK-1/2 but not p38 and JNK. A transient elevation of c-Fos mRNA was induced by OSM, but PD 98059 (MEK inhibitor), fludarabine (signal transducer and activator of transcription 1 [STAT-1] inhibitor), and piceatannol (STAT-3 and STAT-5 inhibitor) abolished this effect. Electrophoretic mobility shift assay revealed that OSM stimulated AP-1-DNA binding, which was also abolished by PD 98059, fludarabine, and piceatannol. Supershift study further confirmed the role of c-Fos in the above interaction. PD 98059, fludarabine, piceatannol, and curcumin (AP-1 inhibitor) inhibited the OSM-induced expression of CCL2.

CONCLUSION

OSM induces CCL-2 expression in osteoblasts. Activation of the MEK/ERK and STAT pathways, which leads to c-Fos expression and AP-1-DNA binding, is involved in the process. The signaling requires tyrosine kinase and PKC but not COX-2.

Growth plate damage, a feature of juvenile idiopathic arthritis, can be induced by adenoviral gene transfer of oncostatin M: a comparative study in gene-deficient mice

OBJECTIVE

To investigate the involvement of proinflammatory and destructive mediators in oncostatin M (OSM)-induced joint pathology, using gene-deficient mice.

METHODS

An adenoviral vector expressing murine OSM was injected into the joints of naive wild-type mice and mice deficient for interleukin-1 (IL-1), IL-6, tumor necrosis factor alpha (TNFalpha), or inducible nitric oxide synthase (iNOS). Reverse transcription-polymerase chain reaction was used to study gene expression. Inflammation and cartilage proteoglycan (PG) depletion were assessed by histology. OSM and IL-1 levels in synovial fluid from patients with juvenile idiopathic arthritis (JIA) were measured by enzyme-linked immunosorbent assay.

RESULTS

Adenoviral expression of murine OSM led to joint inflammation, bone apposition, chondrophyte formation, articular cartilage PG depletion, and VDIPEN neoepitope expression in wild-type mice. A unique and consistent observation was the focal PG depletion and disorganization of the growth plate cartilage during the first week of inflammation. Synovial IL-1beta, IL-6, TNFalpha, and iNOS gene expression was strongly induced. Of these factors, only deficiency in IL-1 markedly reduced inflammation and PG depletion and completely prevented growth plate damage. In addition, this is the first study in which OSM was detected in JIA synovial fluid. Most samples were also IL-1beta positive.

CONCLUSION

IL-1, but not IL-6, TNFalpha, or iNOS, plays an important role in joint disease induced by intraarticular gene transfer of OSM in mice. The effect of OSM on murine connective tissue and the presence of OSM in human synovial fluid make involvement of OSM in human arthropathies very likely.

Inhibition of heparin synthesis by methotrexate in rats in vivo

The content and synthesis of heparin and mast cell-dependent skin oedema (as an indirect evaluation of histamine and serotonin content) were investigated in the rat skin after chronic treatment with compound 48/80, a mast cell degranulating substance. The effect of methotrexate, a folic acid analogue that interrupts the synthesis of DNA and RNA, on heparin synthesis and amine storage also was evaluated in rat skin. The heparin content at 6 and 240 hr after treatment with compound 48/80 was reduced markedly (86 and 64%, respectively). At 6 hr, heparin synthesis increased 3.1-fold compared with control animals; maximal synthesis occurred at 24 hr post-treatment (12.8-fold increase), decaying at 240 hr (2.4-fold increase). The dermatan sulfate content and synthesis were not affected by treatment with compound 48/80. Autoradiographic analysis revealed that methotrexate (2.5mg/kg for 3 consecutive days) abolished heparin synthesis at 6, 24, and 72 hr after compound 48/80 treatment, without affecting dermatan sulfate synthesis. The oedema induced by intradermal injection of compound 48/80 (1 microg/site) into the rat skin was decreased significantly at 6 hr after chronic treatment with this compound, but was restored completely 72 hr post-treatment. This pattern of oedematogenic response was also observed in the methotrexate-treated rats. In conclusion, our results show that methotrexate suppresses heparin synthesis without affecting the synthesis of either dermatan sulfate or the co-stored amines histamine/serotonin (as evaluated by measuring the mast cell-dependent oedema), suggesting that the enzyme system involved in heparin synthesis is inducible.

The reprogrammed host: Chlamydia trachomatis-induced up-regulation of glycoprotein 130 cytokines, transcription factors, and antiapoptotic genes

OBJECTIVE

Infection with Chlamydia trachomatis is a known cause of sexually transmitted diseases, eye infections (including trachoma), and reactive arthritis (ReA). Because the mechanisms of Chlamydia-induced changes leading to ReA are poorly defined, this study sought to identify the target genes involved at the molecular level.

METHODS

Chlamydia-induced changes in host cells were investigated by combining a screening technique, which utilized complementary DNA arrays on C trachomatis-infected and mock-infected epithelial HeLa cells, with real-time reverse transcription-polymerase chain reaction or enzyme-linked immunosorbent assay of gene products. Some responses were additionally demonstrated on human primary chondrocytes and a human synovial fibroblast cell line, both of which served as model cells for ReA.

RESULTS

Eighteen genes (of 1,176) were found to be up-regulated after 24 hours of infection with this obligate intracellular bacterium, among them the glycoprotein 130 family members IL-11 and LIF, the chemokine gene MIP2-alpha, the transcription factor genes EGR1, ETR101, FRA1, and c-jun, the apoptosis-related genes IEX-1L and MCL-1, adhesion molecule genes such as ICAM1, and various other functionally important genes. In the context of this rheumatic disease, the cytokines and transcription factors seem to be especially involved, since various connections to chondrocytes, synoviocytes, bone remodeling, joint pathology, and other rheumatic diseases have been demonstrated.

CONCLUSION

Infection with C trachomatis seems to reprogram the host cells (independent of activation by lipopolysaccharide or other ultraviolet-resistant bacterial components) at various key positions that act as intra- or intercellular switches, suggesting that these changes and similar Chlamydia-induced functional alterations constitute an important basis of the pathogenic inflammatory potential of these cells in ReA. Our results suggest that this approach is generally useful for the broad analysis of host-pathogen interactions involving obligate intracellular bacteria, and for the identification of target genes for therapeutic intervention in this rheumatic disease.

Leukaemia inhibitory factor (LIF): a cytokine of emerging importance in chronic airway inflammation

Inflammation is a complex set of mechanisms by which tissues respond to an injury. These responses involve the coordinated interaction between the nervous and immune systems. An integral part of this interaction is the release of a variety of cytokines that regulate cellular and molecular responses. Leukaemia Inhibitory Factor (LIF), a member of the IL-6 family of cytokines, has been shown to be an integral component of the interface between nerves and the immune system. However, little is known about this cytokine in the context of normal lung function or indeed, inflammation. Evidence is emerging that this cytokine may play an important role in regulating the neural-immune system interaction during acute inflammatory insult and the subsequent healing and restitution process. However, LIF may act as either a pro- or antiinflammatory cytokine, depending on the cell type and a number of other variables. In this review, the role of LIF in airway inflammation and resolution of inflammation is discussed. In particular, recent work suggesting that LIF is a mediator of bi-directional cross-talk between neural tissue and the immune system is highlighted.

Synergistic effects of glycoprotein 130 binding cytokines in combination with interleukin-1 on cartilage collagen breakdown

OBJECTIVE

To determine whether other glycoprotein 130 (gp130) binding cytokines can mimic the effects of oncostatin M (OSM) in acting synergistically with interleukin-1alpha (IL-1alpha) to induce cartilage collagen breakdown and collagenase expression, and to determine which receptors mediate these effects.

METHODS

The release of collagen and proteoglycan was assessed in bovine and human cartilage explant cultures. Messenger RNA (mRNA) and protein production from immortalized human chondrocytes (T/C28a4) was analyzed by Northern blotting and specific enzyme-linked immunosorbent assays. Collagenase activity was measured by bioassay. Cell surface receptors were detected by flow cytometry.

RESULTS

OSM in combination with IL-1alpha caused a rapid synergistic induction of matrix metalloproteinase 1 mRNA, which was sustained over a 72-hour period. Flow cytometric analyses detected both the OSM-specific receptor and the gp130 receptor at the chondrocyte cell surface, but failed to detect the leukemia inhibitory factor receptor (LIFR). Cartilage degradation assays revealed that, of the gp130 binding cytokines, only OSM and IL-6, in the presence of its soluble receptor (sIL-6R), were able to act synergistically with IL-1alpha to promote collagen release.

CONCLUSION

This study demonstrates that IL-6 can mimic OSM in synergizing with IL-1alpha to induce chondrocyte-mediated cartilage collagen breakdown and collagenase production. In order to have this effect, IL-6 requires the presence of its soluble receptor. The apparent absence of LIFR explains why other gp130 binding cytokines do not act in synergy with IL-1alpha. Since OSM, IL-6, and sIL-6R levels have all been shown to be elevated in the rheumatoid joint, our findings suggest that these cytokines may be key mediators of cartilage collagen catabolism in the inflammatory arthritides.

Insulin-like growth factor 1 blocks collagen release and down regulates matrix metalloproteinase-1, -3, -8, and -13 mRNA expression in bovine nasal cartilage stimulated with oncostatin M in combination with interleukin 1alpha

OBJECTIVE

To investigate the effect of insulin-like growth factor 1 (IGF1) on the release of collagen, and the production and expression of matrix metalloproteinases (MMPs) induced by the proinflammatory cytokine interleukin 1alpha (IL1alpha) in combination with oncostatin M (OSM) from bovine nasal cartilage and primary human articular chondrocytes.

METHODS

Human articular chondrocytes and bovine nasal cartilage were cultured with and without IGF1 in the presence of IL1alpha or IL1alpha + OSM. The release of collagen was measured by an assay for hydroxyproline. Collagenase activity was determined with the diffuse fibril assay using 3H acetylated collagen. The expression of MMP-1, MMP-3, MMP-8, MMP-13, and tissue inhibitor of metalloproteinase 1 (TIMP-1) mRNA was analysed by northern blot.

RESULTS

IGF1 can partially inhibit the release of collagen induced by IL1alpha or IL1alpha + OSM from bovine nasal cartilage. This was accompanied by a reduced secretion and activation of collagenase by bovine nasal cartilage. IGF1 can also down regulate IL1alpha or IL1alpha + OSM induced MMP-1, MMP-3, MMP-8, and MMP-13 mRNA expression in human articular chondrocytes and bovine chondrocytes. It had no significant effect on the production and expression of TIMP-1 mRNA in chondrocytes.

CONCLUSION

This study shows for the first time that IGF1 can partially block the release of collagen from cartilage and suggests that down regulation of collagenases by IGF1 may be an important mechanism in preventing cartilage resorption initiated by proinflammatory cytokines.

gp130 Cytokine family and bone cells

Bone tissue is continually being remodelled according to physiological circumstances. Two main cell populations (osteoblasts and osteoclasts) are involved in this process, and cellular activities (including cell differentiation) are modulated by hormones, cytokines and growth factors. Within the last 20 years, many factors involved in bone tissue metabolism have been found to be closely related to the inflammatory process. More recently, a cytokine family sharing a common signal transducer (gp130) had been identified, which appears to be a key factor in bone remodelling. This family includes interleukin 6, interleukin 11, oncostatin M, leukaemia inhibitory factor, ciliary neurotrophic factor and cardiotrophin-1. This paper provides an exhaustive review of recent knowledge on the involvement of gp130 cytokine family in bone cell (osteoblast, osteoclast, etc.) differentiation/activation and in osteoarticular pathologies.

Murine oncostatin M stimulates mouse synovial fibroblasts in vitro and induces inflammation and destruction in mouse joints in vivo

Oncostatin M (OSM) is a multifunctional cytokine, a member of the interleukin-6/leukemia inhibitory factor (IL-6/LIF) family, that can regulate a number of connective-tissue cell types in vitro including cartilage and synovial tissue-derived fibroblasts, however its role in joint inflammation in vivo is not clear. We have analyzed murine OSM (muOSM) activity in vitro and in vivo in mouse joint tissue, to determine the potential role of this cytokine in local joint inflammation and pathology. The effects of muOSM and other IL-6/LIF cytokines on mouse synovial fibroblast cultures were assessed in vitro and showed induction of monocyte chemotactic protein-1, interleukin-6, and tissue inhibitor metalloproteinase-1, as well as enhancement of colony growth in soft agarose culture. Other IL-6/LIF cytokines including IL-6, LIF, or cardiotrophin-1, did not have such effects when tested at relatively high concentrations (20 ng/ml). To assess effects of muOSM in articular joints in vivo, we used recombinant adenovirus expressing muOSM cDNA (AdmuOSM) and injected purified recombinant virus (10(6) to 10(8) pfu) intra-articularly into the knees of various mouse strains. Histological analysis revealed dramatic alterations in the synovium but not in synovium of knees treated with the control virus Ad-dl70 or knees treated with Adm-IL-6 encoding biologically active murine IL-6. AdmuOSM effects were characterized by increases in the synovial cell proliferation, infiltration of mononuclear cells, and increases in extracellular matrix deposition that were evident at day 4, but much more marked at days 7, 14, and 21 after administration. The synovium took on characteristics similar to pannus and appeared to contact and invade cartilage. Collectively, these results provide good evidence that OSM regulates synovial fibroblast function differently than other IL-6-type cytokines, and can induce a proliferative invasive phenotype of synovium in vivo in mice on overexpression. We suggest that OSM may contribute to pathology in arthritis.

Transforming growth factor beta1 blocks the release of collagen fragments from boving nasal cartilage stimulated by oncostatin M in combination with IL-1alpha

Oncostatin M in combination with interleukin-1 (IL-1) induced a rapid and reproducible release of collagen from bovine nasal cartilage in culture. This release was accompanied by a high collagenolytic activity and low or absent tissue inhibitor of metalloproteinase-1 activity in the culture medium. Transforming growth factor-beta1 was able to block this release of collagen from the tissue, and reduce the expression and secretion of collagenases whilst maintaining TIMP-1 levels from bovine nasal chondrocytes. This study shows for the first time that TGF-beta1 can protect cartilage collagen from destruction.

Soluble glycoprotein 130 (gp130) attenuates OSM- and LIF-induced cartilage proteoglycan catabolism

Oncostatin M (OSM) and leukaemia inhibitory factor (LIF) exhibit pleiotropic biological activities and share many structural and genetic features. The two cytokines bind with high affinity to the same receptor (LIF/OSM receptor), which consists of the LIF receptor alpha chain (LIFRalpha) and the signal transduction unit gp130. A soluble form of the beta chain of the receptor complex called soluble gp130 (sgp130) has been cloned. In this study, we sought to determine whether recombinant sgp130 or anti-gp130 Ab could attenuate the resorption of proteoglycans induced by OSM and LIF in articular cartilage explants. The results show that at high concentrations sgp130 is capable of attenuating both LIF and OSM mediated resorption. In contrast, anti-gp130 Ab selectively inhibited the stimulation of proteoglycan (PG) release by OSM, albeit minimally. The failure of anti-gp130 to attenuate LIF stimulated PG resorption may be due to the normal interaction of LIF with LIFRalpha and unfettered heterodimerization of LIFRalpha with gp130 in the presence of the antibody. The results indicate that sgp130 and anti-gp130 can modulate cartilage PG metabolism in vitro. Whether sgp130 may have therapeutic activity in models of arthritis or indeed in arthritic diseases remains to be determined.

Oncostatin M induces leukocyte infiltration and cartilage proteoglycan degradation in vivo in goat joints

OBJECTIVE

To evaluate the effect of intraarticular injections of recombinant human oncostatin M (rHuOSM) in the goat joint.

METHODS

One milliliter of endotoxin-free normal saline (vehicle) containing either 40 ng, 200 ng, or 1,000 ng of rHuOSM was injected into the right radiocarpal joints (RCJs) of 12 male angora goats, while the left RCJs were injected with an equivalent volume of vehicle alone. In subsequent studies, the right and left RCJs of 8 male angora goats were injected with 200 ng of rHuOSM, and 1 hour later, the right RCJs were injected with either 5 microg of recombinant murine leukemia inhibitory factor binding protein (rMuLBP) or 1 mg of recombinant human interleukin-1 receptor antagonist (rHuIL-1Ra) in 1 ml of vehicle, while the left RCJs received 1 ml of vehicle alone. Goat joints were examined for clinical features of inflammation, and synovial fluid (SF) was aspirated on day 0 (before injection) and at days 2 and 6 postinjection.

RESULTS

Injections of rHuOSM stimulated dose-dependent increases in the carpal:metacarpal ratio, SF volume, and SF leukocyte numbers, and stimulated dose-dependent decreases in the cartilage proteoglycan (PG) content ex vivo and PG synthesis. No significant changes were observed in the control joints that received saline alone, or between RCJs that were injected with 200 ng rHuOSM followed by 5 microg rMuLBP and RCJs that were injected with 200 ng of rHuOSM alone, except in respect to synovial fluid keratan sulfate concentrations, where a modest statistically significant reduction was observed in the joints injected with the combination of rHuOSM and rMuLPB. In contrast, RCJs injected with 200 ng rHuOSM followed by 1 mg of rHuIL-1Ra had significantly lower SF volumes (P<0.0001) and a significantly higher rate of ex vivo PG synthesis (P<0.0001).

CONCLUSION

These results indicate that rHuOSM stimulates inflammation and modulates cartilage PG metabolism in vivo. Some of the effects of rHuOSM in vivo appear to be due, in part, to elaboration of IL-1. Even at very high doses, however, the rHuIL-1Ra did not attenuate OSM-mediated cartilage PG resorption. Thus, OSM has the potential to contribute to synovitis in vivo and can stimulate cartilage PG resorption in vivo, independent of IL-1.

Oncostatin M: signal transduction and biological activity

Oncostatin M (OSM) is a multifunctional cytokine produced by activated T lymphocytes and monocytes that is structurally and functionally related to the subfamily of cytokines known as the IL-6-type cytokine family. OSM shares properties with all members of this family of cytokines, but is most closely related structurally and functionally to LIE OSM acts on a wide variety of cells and elicits diversified biological responses in vivo and in vitro which suggest potential roles in the regulation of gene activation, cell survival, proliferation and differentiation. OSM and LIF can bind to the same functional receptor complex (LIF-receptor beta and gp130 heteromultidimers) and thus mediate overlapping spectra of biological activities. There is a second specific beta receptor that binds OSM with high affinity and also involves the subunit gp130. The two receptors for OSM can be functionally different and be coupled to different signal transduction pathways. OSM-specific receptors are expressed in a wide variety of cell types and do not possess an intrinsic tyrosine kinase domain, but the JAK/STAT tyrosine kinase pathway mediates signal transduction.

Leukemia inhibitory factor, Interleukin 6, and other cytokines using the GP130 transducing receptor: roles in inflammation and injury

Inflammation refers to a complex set of mechanisms by which tissues respond to injury and infection. Among the many soluble mediators associated with this process, cytokines are known to be crucial in regulating a variety of cellular and molecular events. Leukemia inhibitory factor (LIF), interleukin 6 (IL-6), IL-11, and possibly other members of this cytokine family are key mediators in various inflammatory processes such as the acute-phase reaction, tissue damage, and infection. These cytokines can act in both pro-inflammatory and anti-inflammatory ways, depending on a number of variables. We emphasize here recent work utilizing knockout mice, which has highlighted the roles of LIF and IL-6, particularly in interactions between the immune and nervous systems.

Oncostatin M Up-Regulates Tissue Inhibitor of Metalloproteinases-3 Gene Expression in Articular Chondrocytes via De Novo Transcription, Protein Synthesis, and Tyrosine Kinase- and Mitogen-Activated Protein Kinase-Dependent Mechanisms

Cytokines and growth factors regulate physiologic and pathologic turn-over of cartilage extracellular matrix (ECM) by altering the balance between tissue inhibitors of metalloproteinases (TIMPs) and matrix metalloproteinases (MMPs). Oncostatin M (OSM) is a cytokine of the IL-6 family whose levels are increased in the serum and synovial fluids of patients with rheumatoid arthritis. We examined responsiveness of the TIMP-3 gene to OSM in articular chondrocytes and studied the regulatory and signaling mechanisms of this response. OSM induced TIMP-3 mRNA and protein expression in a dose- and time-dependent fashion. Concomitantly, stromelysin-1 and collagenase-1 RNA and activities were also induced. A cartilage matrix growth factor, TGF-β, induced TIMP-3, but combined OSM and TGF-β did not further increase the extent of induction, suggesting a lack of synergy between the two. OSM induction of TIMP-3 gene expression was dependent upon de novo protein synthesis and transcription. RNA decay time-courses suggested that the OSM-mediated increase of TIMP-3 RNA was not due to enhanced message stability and, along with inhibition by actinomycin-D, suggested a transcriptional control. The antiinflammatory glucocorticoid, dexamethasone, down-regulated this augmentation. Investigation of the signaling mechanisms revealed that protein tyrosine kinase inhibitors genistein and herbimycin A, as well as the specific mitogen-activated protein kinase (MAPK) kinase inhibitor PD98059, suppressed OSM-induced TIMP-3 message expression, suggesting the involvement of tyrosine kinases and mitogen-activated protein kinase cascades in the signaling of OSM leading to TIMP-3 RNA enhancement. Thus OSM can potentially alter the cartilage matrix metabolism by regulating genes like TIMP-3 and matrix metalloproteinases.

Chondrocyte-mediated catabolism of aggrecan: aggrecanase-dependent cleavage induced by interleukin-1 or retinoic acid can be inhibited by glucosamine

A rat chondrosarcoma cell line and bovine cartilage explants have been used to study the control of aggrecan degradation by chondrocytes treated with interleukin-1 (IL-1) or retinoic acid (RA). Aggrecan fragment analysis with anti-neo-epitope antibodies suggests that aggrecanase (an as yet unidentified enzyme) is the only aggrecan-degrading proteinase active in these cultures. With rat cells, aggrecanase converts the aggrecan core protein into two major G1-domain-bearing products (60 kDa with a C-terminal Glu-373, and 220 kDa with a C-terminal Glu-1459). Both products were quantified on a standardized Western analysis system with a G1-specific antibody. Immunoblots were analysed by scanning densitometry and the sensitivity, linearity and reproducibility of the assay were established. With rat cells the aggrecanase response to IL-1 was optimal at about 2 mM glutamine, but was progressively inhibited at higher concentrations, with about 90% inhibition at 10 mM glutamine. Such inhibition by glutamine was not, however, observed with bovine explants. On the other hand, marked inhibition of aggrecanase-dependent cleavage was observed with both rat cells and bovine explants when d(+)-glucosamine was included at concentrations above 2 mM. Inhibition was apparently not due to cytotoxicity or interference with IL-1 signalling, since biosynthetic activity was not inhibited and inhibition of the aggrecanase response was also obtained when RA was used as the catabolic stimulator. Possible mechanisms for the inhibition of the aggrecanase response by glucosamine in chondrocytes treated with IL-1 or RA are discussed.

The role of oncostatin M in animal and human connective tissue collagen turnover and its localization within the rheumatoid joint

OBJECTIVE

To study the interaction of interleukin-1alpha (IL-1alpha) and oncostatin M (OSM) in promoting cartilage collagen destruction.

METHODS

Bovine, porcine, and human cartilage and human chondrocytes were studied in culture. The levels of collagenase (matrix metalloproteinase 1 [MMP-1]) and tissue inhibitor of metalloproteinases 1 (TIMP-1) were measured by bioassay and enzyme-linked immunosorbent assay (ELISA). The levels of OSM in rheumatoid synovial fluid were measured by ELISA.

RESULTS

When combined with OSM, IL-1alpha, IL-1beta, and tumor necrosis factor alpha released proteoglycan and collagen from cartilage. OSM was the only member of the IL-6 family to have this effect. Human tendon also responded to IL-1alpha and OSM. OSM increased the production of MMP-1 and TIMP-1 but when combined with IL-1alpha, synergistically promoted MMP-1 production in human chondrocytes and synovial fibroblasts. High levels of OSM were found in human rheumatoid synovial fluids, and confocal microscopy showed that OSM was produced by macrophages in rheumatoid synovial tissue.

CONCLUSION

These results highlight an important new mechanism by which there is irreversible loss of collagen from cartilage.

Detection of oncostatin M in synovial fluid from patients with rheumatoid arthritis

OBJECTIVE

To measure oncostatin M (OSM) in synovial fluid from patients with rheumatoid arthritis (RA) and osteoarthritis (OA).

METHODS

20 samples of synovial fluid from patients with RA and 10 samples from patients with OA were examined using an OSM specific sandwich ELISA.

RESULTS

OSM was detected at concentrations ranging from 2.36 to 901.82 pg/ml in 18 (90%) of 20 samples of synovial fluid from RA patients. There was no detectable OSM in synovial fluid from OA patients. In the RA patients, the OSM concentration in synovial fluid correlated significantly with the synovial fluid white blood cell count (r = 0.67, p < 0.01), but not with other laboratory parameters of disease activity.

CONCLUSION

These findings suggest that OSM may contribute to joint inflammation in RA.