Expression of interleukin-6 in osteoarthritic chondrocytes and effects of fluid-induced shear on this expression in normal human chondrocytes in vitro

This study tested the effect of fluid-induced shear on interleukin-6 expression in normal human articular chondrocytes in vitro. As determined by Northern blot analysis, interleukin-6 mRNA expression occurs in chondrocytes from osteoarthritic cartilage but not in normal chondrocytes. Applying fluid-induced shear stress to primary high density cultures of chondrocytes increased interleukin-6 mRNA signal 4-fold at 1 hour and 10 to 15-fold at 48 hours compared with unsheared control cultures. At 48 hours, fluid-induced shear stress increased interleukin-6 protein levels in the culture medium 9 to 10-fold compared with unsheared controls, mRNA signals for interleukin-1α, interleukin-1β, and tumor necrosis factor-α in RNA from sheared or control chondrocytes were not detected by Northern blotting. Transforming growth factor-β mRNA signal was detectable but was not affected by shear. In contrast, human lung fibroblasts (WI-38) responded to fluid-induced shear with increased signal for transforming growth factor-β but not interleukin-6, mRNA. Both cell types did respond to interleukin-1α with increased interleukin-6 mRNA signal. These data demonstrate that distortional forces, such as fluid-induced shear stress, alter interleukin-6 levels in normal chondrocytes in vitro and suggest that increased interleukin-6 expression in osteoarthritic cartilage may result, in part, from alterations in the mechanical loading of the tissue.     

Glucosamine sulfate modulates dysregulated activities of human osteoarthritic chondrocytes in vitro

OBJECTIVE: The efficacy of glucosamine sulfate (GS) in the symptomatic treatment of patients with osteoarthritis (OA) is suggested to be mediated by still unknown effects on the altered OA cartilage. DESIGN: Using human OA chondrocytes in culture, the effects of GS on protein synthesis, caseinase, collagenase, phospholipase A2 (PLA2) and protein kinase C (PKC) activities as well as production of nitric oxide and cyclic AMP were studied in both cells and culture medium. RESULTS: GS significantly reduced PLA2 activity, and more modestly collagenase activity, in the OA chondrocytes in a dose-dependent manner. By contrast, PLA2 and collagenase activity of the culture medium was not modified. No effects on caseinase activity was seen. GS significantly and dose-dependently increased protein synthesis. GS did not modify nitric oxide and cAMP production but significantly increased PKC production. CONCLUSION: GS modified cultured OA chondrocyte metabolism by acting on PKC, cellular PLA2, protein synthesis and possibly collagenase activation. Extrapolation of the effect to the in-vivo situation remains hypothetical but they might represent some possible mechanisms of action of the drug in human.     

Investigation of the direct effects of salmon calcitonin on human osteoarthritic chondrocytes

Background

Regional musculoskeletal pain such as back or shoulder pain are commonly reported symptoms in the community. The extent of consultation to primary care with such problems is unknown as a variety of labels may be used to record such consultations. The objective was to classify musculoskeletal morbidity codes used in routine primary care by body region, and to determine the annual consultation prevalence of regional musculoskeletal problems.

Methods

Musculoskeletal codes within the Read morbidity Code system were identified and grouped by relevant body region by four GPs. Consultations with these codes were then extracted from the recorded consultations at twelve general practices contributing to a general practice consultation database (CiPCA). Annual consultation prevalence per 10,000 registered persons for the year 2006 was determined, stratified by age and gender, for problems in individual regions and for problems affecting multiple regions.

Results

5,908 musculoskeletal codes were grouped into regions. One in seven of all recorded consultations were for a musculoskeletal problem. The back was the most common individual region recorded (591 people consulting per 10,000 registered persons), followed by the knee (324/10,000). In children, the foot was the most common region. Different age and gender trends were apparent across body regions although women generally had higher consultation rates. The annual consultation-based prevalence for problems encompassing more than one region was 556 people consulting per 10,000 registered persons and increased in older people and in females.

Conclusions

There is an extensive and varied regional musculoskeletal workload in primary care. Musculoskeletal problems are a major constituent of general practice. The output from this study can be used as a resource for planning future studies.     

Protective effects of intermittent hydrostatic pressure on osteoarthritic chondrocytes activated by bacterial endotoxin in vitro.

The role of continuous passive motion (CPM) in the management of septic arthritis and inflammatory arthritis remains of interest. CPM produces cyclic variations in intraarticular pressure that facilitates transport of fluid, nutrients, and solutes within and/or across the joint and stimulates chondrocyte metabolism. However, the precise mechanisms mediating the responses of chondrocytes to joint motion remain unclear. This study tested the hypothesis that dynamic mechanical loading counteracts effects of bacterial lipopolysaccharide (LPS), an inflammatory mediator, on chondrocyte metabolism. Intermittent hydrostatic pressure (IHP) (10 MPa for 4 h) was applied to human chondrocytes pretreated with LPS (1 microg/ml for 18 h). LPS activation of chondrocytes decreased mRNA signal levels of type II collagen by 67% and aggrecan by 56% and increased nitric oxide by 3.1-fold, monocyte chemotactic protein-1 mRNA signal levels by 6.5-fold, and matrix metalloproteinase-2 mRNA signal levels by 1.3-fold. Application of IHP to LPS-activated chondrocytes decreased nitric oxide synthase mRNA signal levels and nitric oxide levels in the culture medium. Exposure of LPS-activated chondrocytes to IHP upregulated type II collagen and aggrecan mRNA signal levels by 1.7-fold, relative to chondrocytes activated by LPS and maintained without loading. In addition, application of IHP decreased the upregulation in signal levels of monocyte chemotactic factor-1 and matrix metalloproteinase-2 following LPS activation by 45% and 15%, respectively. These data show that mechanical loading counteract effects of inflammatory agents, such as bacterial LPS, and suggest that postinfection sequelae are influenced by the presence or absence of joint loading.     

The in vitro effects of dehydroepiandrosterone on chondrocyte metabolism

OBJECTIVE: To investigate the in vitro effects of dehydroepiandrosterone (DHEA) on neonatal rat chondrocytes. DESIGN: Chondrocytes isolated from neonatal rat cartilage were cultured in three-dimensionally agarose beads and were treated with DHEA. METHODS: Primary culture of chondrocytes was harvested from newborn Wistar rats. The DHEA effects on chondrocyte activities were evaluated by analyzing chondrocyte proliferation, matrix protein synthesis, gene expressions of collagen, matrix metalloproteinase-1, -3 and -13 (MMP-1, -3 and -13), and cyclooxygenase-2 (COX-II), and protein synthesis of interleukin-6 (IL-6), prostaglandin E2 (PGE2) and tissue inhibitor of metalloproteinase-1 (TIMP-1). RESULTS: The DHEA treatment did affect chondrocyte proliferation and glycosaminoglycan (GAG) synthesis. DHEA suppressed the expression of MMP-1, -3 and -13 genes and PGE2 protein synthesis enhanced by lipopolysaccharide (LPS) while the COX-II and inducible nitric oxide synthase (iNOS) gene expressions were down-regulated by DHEA. CONCLUSIONS: Our study demonstrates that DHEA has an ability to modulate the imbalance between MMPs and PGE2 in the neonatal chondrocytes which suggest that it has a potential protective role against articular cartilage damage.     

Effects of hyaluronan on proteoglycan content of osteoarthritic chondrocytes in vitro.

PURPOSE: To investigate the effect of hyaluronic acid (HA) on proteoglycan (PG) concentration in alginate cultures of human osteoarthritic chondrocytes and to analyze whether HA exhibit anti-degradative effects in the presence of the cytokine IL-1beta. METHODS: Cartilage samples from ten patients with osteoarthritis of the knee were harvested and chondrocytes were cultivated in alginate beads. Four groups were cultured: control group with and without IL-1beta (500 pg/ml) and HA group (100 microg/ml) with and without IL-1beta (500 pg/ml). PG concentration was estimated by a dimethylmethylene blue assay. To assess cell proliferation, we measured DNA content fluorometrically. RESULTS: The proliferation rate (DNA) was unchanged in all culture groups. In the control-group PG/DNA (ng/ng) concentration was 27.1 +/- 7.2. Supplementation of the medium with HA decreased PG concentration to 25.3 +/- 6.9 (p < 0.05). After administration of IL-1beta PG/DNA concentration dropped to 23.1 +/- 6.0 (p < 0.01). By contrast HA treatment of IL-1beta stimulated chondrocytes did not further decrease PG concentration (23.9 +/- 6.1). In fact the negative effect of isolated HA application was inverted if HA was given with IL-1beta (p < 0.05). CONCLUSIONS: In osteoarthritic chondrocytes cultured phenotypically stable, HA could exhibit protective effects only in the presence of the degradative cytokine IL-1beta. Thus, the reported anti-inflammatory effects of HA to cartilage matrix seem to be more indirect by blocking degradative effects of cytokines to the matrix.     

Homeostasis of the extracellular matrix of normal and osteoarthritic human articular cartilage chondrocytes in vitro

OBJECTIVE: In normal articular cartilage cells, the IGFRI/insulin-like growth factor 1 (IGF-1) autocrine pathway was shown to overrule the catabolic effects of the IL-1/IL-1RI pathway by up-regulation of the IL-1RII decoy receptor. The activity of the IGF-1/IGFR1 and IL-1/IL-1R pathways, and of the IL-1RII control mechanism in the synthesis and turnover of the extracellular matrix (ECM) by chondrocytes from normal and osteoarthritic (OA) articular cartilage was compared in order to identify possible therapeutic targets of this disease. METHODS: Phenotypically stable human articular cartilage cells were obtained from normal and OA cartilage of the same knee showing focal OA. The cells were cultured in alginate beads over 1 week to re-establish the intracellular cytokine and growth factors, to reexpress the respective plasma membrane receptors and to reach equilibrium in accumulated cell-associated matrix (CAM) compounds. Following liberation of the cells from the alginate beads, the levels of cell-associated matrix (CAM) aggrecan, type II collagen and fibronectin, of intracellular IGF-1, IL-1alpha and beta and of their respective plasma membrane-bound receptors, IGFR1, IL-1RI and the decoy receptor IL-1RII, were assayed using flow cytometry. RESULTS: Coordinated production and accumulation of CAM aggrecan and type II collagen under the effect of the IGFR1/IGF-1 autocrine pathway-as documented for chondrocytes from healthy controls-was absent when the chondrocytes had been obtained from OA joints. When compared with cells obtained from normal tissues, chondrocytes from fibrillated OA cartilage expressed significantly higher intracellular IGF-1 levels and plasma membrane-bound IGFR1. At the same time, significantly higher intracellular IL-1alpha and beta levels and upregulated plasma membrane-bound IL-1RI were observed. Plasma membrane-bound IL-1RII decoy receptor was downregulated in OA chondrocytes. The levels of CAM aggrecan, type II collagen and fibronectin were significantly reduced in the chondrocytes obtained from pathological tissue. CONCLUSION: Paired analysis of normal and OA chondrocytes from the same knee joint has shown an enhanced capacity of chondrocytes from OA cartilage to produce ECM macromolecules. However, the same cells have increased catabolic signalling pathways. As a consequence of this increased IL-1 activity and the reduced amounts of IL-1RII decoy receptor, less of the produced ECM macromolecules may persist in the CAM of the OA chondrocytes.     

The in vitro effects of bupivacaine on articular chondrocytes

We have studied the effects of bupivacaine on human and bovine articular chondrocytes in vitro. Time-lapse confocal microscopy of human articular chondrocytes showed > 95% cellular death after exposure to 0.5% bupivacaine for 30 minutes. Human and bovine chondrocytes exposed to 0.25% bupivacaine had a time-dependent reduction in viability, with longer exposure times resulting in higher cytotoxicity. Cellular death continued even after removal of 0.25% bupivacaine. After exposure to 0.25% bupivacaine for 15 minutes, flow cytometry showed bovine chondrocyte viability to be 41% of saline control after seven days. After exposure to 0.125% bupivacaine for up to 60 minutes, the viability of both bovine and human chondrocytes was similar to that of control groups. These data show that prolonged exposure 0.5% and 0.25% bupivacaine solutions are potentially chondrotoxic.     

Intermittent hydrostatic pressure inhibits matrix metalloproteinase and pro-inflammatory mediator release from human osteoarthritic chondrocytes in vitro

OBJECTIVE: This study tested the hypothesis that intermittent hydrostatic pressure applied to human osteoarthritic chondrocytes modulates matrix metalloproteinase and pro-inflammatory mediator release in vitro. DESIGN: Human osteoarthritic articular chondrocytes were isolated and cultured as primary high-density monolayers. For testing, chondrocyte cultures were transferred to serum-free medium and maintained without loading or with exposure to intermittent hydrostatic pressure (IHP) at 10 MPa at a frequency of 1 Hz for periods of 6, 12 and 24 h. Levels of matrix metalloproteinase-2, -9 (MMP-2, -9), tissue inhibitor of metalloproteinase-1 (TIMP-1), and the pro-inflammatory mediators, interleukin-6 (IL-6) and monocyte chemoattractant protein-1 (MCP-1), released into the culture medium were assessed by ELISA. Matrix metalloproteinase activity was confirmed by zymographic analysis. RESULTS: In the absence of IHP, levels of MMP-2, TIMP-1, IL-6, and MCP-1 in the chondrocyte culture medium increased in a time-dependent manner. Application of IHP decreased MMP-2 levels at all time periods tested, relative to unloaded control cultures maintained for the same time periods. Although 84/82 kDa bands were faintly detectable by zymography, MMP-9 levels were not quantifiable in medium from loaded or unloaded cultures by ELISA. TIMP-1 levels were not altered in response to IHP at any time period tested. IL-6 and MCP-1 levels decreased in cultures exposed to IHP at 12 and 24 h, relative to unloaded control cultures maintained for the same time periods. CONCLUSION: IHP decreased release of MMP-2, IL-6 and MCP-1 by osteoarthritic chondrocytes in vitro suggesting that pressure influences cartilage stability by modulating chondrocyte expression of these degradative and pro-inflammatory proteins in vivo.     

Subchondral bone osteoblasts induce phenotypic changes in human osteoarthritic chondrocytes

OBJECTIVE: To determine the influence of osteoarthritic (OA) phenotype of subchondral osteoblasts on the phenotype of human chondrocytes. METHODS: Human chondrocytes were isolated from OA cartilage and cultured in alginate beads for 4 or 10 days in the absence or in the presence of osteoblasts in monolayer. The osteoblasts were either isolated from non-sclerotic (N) or sclerotic (SC) zones of human subchondral bone. Before co-culture, osteoblasts were incubated for 72 h with or without 1.7 ng/ml interleukin (IL)-1beta, 100 ng/ml IL-6 with its soluble receptor (50 ng/ml) or 10 ng/ml oncostatin M. SOX9, type I, II and X collagen (COL1, COL2, COL10), osteoblasts-stimulating factor (OSF)-1, bone alkaline phosphatase (ALP), parathyroid hormone related peptide (PTHrP) and its receptor (PTH-R) messenger RNA (mRNA) levels in chondrocytes were quantified by real-time polymerase chain reaction. RESULTS: In comparison with chondrocytes cultured alone in alginate beads, chondrocytes after 4 days in co-culture with N or SC osteoblasts expressed significantly less SOX9 and COL2 mRNA. The decrease of SOX9 and COL2 gene expression was significantly more pronounced in the presence of SC than in the presence of N osteoblasts (P<0.001). OSF-1 mRNA level in chondrocyte was increased by both N and SC osteoblasts, but to a larger extent by SC osteoblasts (P<0.001). PTHrP expression in chondrocytes was 21-fold increased by N osteoblasts but four-fold inhibited by SC osteoblasts. PTHrP secretion was also increased by N but reduced by SC osteoblasts. SC, but not N osteoblasts, induced a significant decrease of PTH-R gene expression in chondrocyte. In our experimental conditions, chondrocytes did not express COL1, COL10 or ALP, even after 10 days of co-culture with osteoblasts. CONCLUSIONS: In co-culture, SC subchondral osteoblasts decrease SOX9, COL2, PTHrP and PTH-R gene expression by chondrocytes but increase that of OSF-1. These findings suggest that SC osteoblasts could initiate chondrocyte phenotype shift towards hypertrophic differentiation and subsequently further matrix mineralization.     

Stimulation of proteoglycan production by glucosamine sulfate in chondrocytes isolated from human osteoarthritic articular cartilage in vitro

OBJECTIVE: This study investigated the in-vitro effects of a crystalline glucosamine sulfate (GS) preparation on DNA synthesis and on proteoglycan (PG) and type II collagen (coll II) production by human articular chondrocytes isolated from human osteoarthritic articular cartilage in a 3-dimensional culture system for 4, 8, and 12 days. MATERIALS AND METHODS: Human articular chondrocytes from osteoarthritic femoral heads were isolated from their matrix by collagenase digestion and then cultured in suspension. Under constant agitation, cells aggregated and formed a cluster within a few days. The effects of GS (1-100 micrograms/ml) on chondrocytes were determined by quantifying DNA synthesis (by measurement of [3H]-thymidine uptake) as well as PG and coll II production using radiommunoassays (RIAs) specific for coll II and to human human cartilage PG. Cross-reaction with GS in the RIAs was not detected. Moreover, PG size distribution was determined by exclusion chromatography under associative conditions to determine the association of PG monomers with hyaluronic acid (HA) to form large molecular weight PG aggregates. RESULTS: Under the above conditions, PG production in culture media and chondrocyte clusters was increased by GS (10-100 micrograms/ml). DNA synthesis and coll II production were not modified by GS. In addition, GS did not modify the physico-chemical form of PG produced by cells during culture. CONCLUSIONS: Glucosamine sulfate did not affect DNA synthesis nor coll II production but caused a statistically significant stimulation of PG production by chondrocytes from human osteoarthritic cartilage cultured for up to 12 days in 3-dimensional cultures.     

Expression of vitamin D receptors and matrix metalloproteinases in osteoarthritic cartilage and human articular chondrocytes in vitro

OBJECTIVES: To examine the in situ distributions of vitamin D receptors (VDR) and matrix metalloproteinases (MMPs) in osteoarthritic cartilage for comparison with non-arthritic, normal cartilage; and to assess the in vitro effects of 1alpha,25 dihydroxyvitaminD(3)(1alpha,25(OH)(2)D(3)) on MMPs-1, -3 and -9 and prostaglandin E(2)(PGE(2)) production by cultures of human articular chondrocytes (HAC) shown to be VDR-positive. METHODS: Using immunohistochemistry VDR expression in different specimens of osteoarthritic cartilage (N=11) was compared to that in normal cartilage (N=6), along with the immunodetection of MMPs-1, -3 and -9. The effects of 1alpha25(OH)(2)D(3)on MMP and PGE(2)production by HAC in vitro, with and without stimulation by TNFalpha or phorbol myristate acetate (PMA), was evaluated using ELISA methodology. RESULTS: VDR was demonstrated in HAC of all specimens of osteoarthritic cartilage, especially the superficial zone, whereas only two of five normal cartilage specimens were VDR(+)for a minor proportion of HAC. Immunolocalization of MMPs-1, -3 and -9 was often seen in areas where chondrocytes were VDR(+), and dual immunolocalization has demonstrated individual chondrocytes positive for both VDR and MMP-3 in situ. In vitro, 1alpha25(OH)(2)D(3)alone had no effect on MMP-1, -9 and PGE(2)production by HAC, but MMP-3 production was up-regulated by 1alpha25(OH)(2)D(3)either with or without stimulation with TNFalpha or PMA. By contrast the increased production of MMP-9 and PGE(2)induced by PMA was significantly suppressed by concomitant treatment with 1alpha25(OH)(2)D(3). CONCLUSIONS: The demonstration of VDR expression by HAC in osteoarthritic cartilage was often associated with sites where MMP expression was prevalent, observations in contrast to their virtual absence in normal age-matched cartilage. Together with HAC in vitro studies, the data suggests that 1alpha25(OH)(2)D(3)contributes to the regulation of MMP and PGE(2)production by HAC in osteoarthritic cartilage.     

Effects of shear stress on nitric oxide and matrix protein gene expression in human osteoarthritic chondrocytes in vitro.

Mechanical loading alters articular cartilage metabolism. However, mechanisms underlying intracellular signaling and communication between cells in response to mechanical stresses remain enigmatic. This study tested the hypothesis that shear stress-induced nitric oxide (NO) production participates in the regulation of matrix protein gene expression. The data presented here demonstrate that exposure of human osteoarthritic chondrocytes to a continuously applied shear stress (1.64 Pa) upregulated NO synthase gene expression and increased NO release by 1.8-, 2.4-, and 3.5-fold at 2, 6, and 24 h, respectively. Exposure of chondrocytes to a short duration of shear stress for 2 h resulted in the release of accumulation of NO in the culture medium. Exposure of chondrocytes to shear stress for 2, 6, and 24 h inhibited type II collagen mRNA signal levels by 27%, 18% and 20% after a constant post-shear incubation period of 24 h. Aggrecan mRNA signal levels were inhibited by 30%, 32% and 41% under identical conditions. Addition of an NO antagonist increased type II collagen mRNA signal levels by an average of 1.8-fold (137% of the un-sheared control) and reestablished the aggrecan mRNA signal levels by an average of 1.4-fold after shear stress (92% of the un-sheared control) (ANOVA p < 0.05). These data support the hypothesis that shear stress-induced NO release may influence the development of degenerative joint diseases by inhibiting matrix macromolecule synthesis.     

Characterization of microRNA expression profiles in normal and osteoarthritic human chondrocytes

ABSTRACT: OBJECTIVE: To identify and characterize the expression profile of miRNAs in normal and Osteoarthritis (OA) chondrocytes and to determine their role in the OA. METHODS: Chondrocytes were moved to aggregate culture and evaluated using histological and qPCR techniques. miRNAs were isolated and analyzed using the Agilent Human miRNA Microarray. RESULTS: Of the 723 miRNAs analyzed, 7 miRNAs showed a statistically significant differential expression. Amongst these 7 human miRNAs, 1 was up-regulated in OA chondrocytes (hsa-miR-483-5p) and 6 were up-regulated in normal chondrocytes (hsa-miR-149*, hsa-miR-582-3p, hsa-miR-1227, hsa-miR-634, hsa-miR-576-5p and hsa-miR-641). These profiling results were validated by the detection of some selected miRNAs by qPCR. In silico analyses predicted that key molecular pathways potentially altered by the miRNAs differentially expressed in normal and OA chondrocytes include TGF-beta, Wnt, Erb and mTOR signalling; all of them implicated in the development, maintenance and destruction of articular cartilage. CONCLUSIONS: We have identified 7 miRNAs differentially expressed in OA and normal chondrocytes. Our potential miRNA target predictions and the signalling cascades altered by the differentially expressed miRNAs supports the potential involvement of the detected miRNAs in OA pathology. Due to the importance of miRNA in mediating the translation of target mRNA into protein, the identification of these miRNAs differentially expressed in normal and OA chondrocyte micropellets could have important diagnostic and therapeutic potential. Further studies are needed to know the function of these miRNAs, including the search of their target mRNA genes, which could lead to the development of novel therapeutic strategies for the OA treatment.     

Impaired expression of genes regulating cholesterol efflux in human osteoarthritic chondrocytes

Altered lipid metabolism has been implicated as a critical player in osteoarthritis (OA). Our study aimed to investigate the expression of genes regulating cholesterol efflux in human chondrocytes and to study the effect of an LXR agonist on cholesterol efflux and lipid accumulation in osteoarthritic chondrocytes. ATP‐binding‐cassette transporter A1 (ABCA1), apolipoprotein A1 (ApoA1), and liver X receptors (LXRα and LXRβ) mRNA expression levels were evaluated using real‐time polymerase chain reaction (PCR) and ApoA1 protein levels by Western blot analysis in normal and osteoarthritic articular cartilage samples. Cholesterol efflux was evaluated in osteoarthritic chondrocytes radiolabeled with [1,2(n)‐³H] cholesterol after LXR treatment, while intracellular lipid accumulation was studied after Oil‐red‐O staining. Cholesterol efflux gene expressions were significantly lower in osteoarthritic cartilage compared to normal. Treatment of osteoarthritic chondrocytes with the LXR agonist TO‐901317 significantly increased ApoA1 and ABCA1 expression levels, as well as cholesterol efflux. Additionally, osteoarthritic chondrocytes presented intracellular lipids deposits, while no deposits were found after treatment with TO‐901317. Our findings suggest that impaired expression of genes regulating cholesterol efflux may be a critical player in osteoarthritis, while the ability of the LXR agonist to facilitate cholesterol efflux suggests that it may be a target for therapeutic intervention in osteoarthritis. © 2010 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 28:1033–1039, 2010     

Glucosamine inhibits IL-1beta-induced NFkappaB activation in human osteoarthritic chondrocytes

OBJECTIVE: Glucosamine sulfate (GS) is a commonly used drug for the treatment of osteoarthritis. The mechanism of the action of this drug does, however, remain to be elucidated. In human osteoarthritic chondrocytes (HOC) stimulated with a proinflammatory cytokine, we studied whether GS could modify the NFkappaB activity and the expression of COX-2, a NFkappaB-dependent gene. METHODS: Using HOC in culture stimulated with interleukin-1 beta (IL-1beta), the effects of GS on NFkappaB activation, nuclear translocation of NFkappaB/Rel family members, COX-1 and COX-2 expressions and syntheses and prostaglandin E2 (PGE2) concentration were studied. RESULTS: GS significantly inhibited NFkappaB activity in a dose-dependent manner, as well as the nuclear translocation of p50 and p65 proteins. Furthermore, GS-preincubated IL-1beta-stimulated HOC showed an increase in IkappaBalpha in the cell cytoplasm in comparison with HOC incubated with IL-1beta alone. GS also inhibited the gene expression and the protein synthesis of COX-2 induced by IL-1beta, while no effect on COX-1 synthesis was seen. GS also inhibited the release of PGE2 to conditioned media of HOC stimulated with IL-1beta. CONCLUSIONS: GS inhibits the synthesis of proinflammatory mediators in HOC stimulated with IL-1beta through a NFkappaB-dependent mechanism. Our study further supports the role of GS as a symptom- and structure-modifying drug in the treatment of OA.