Interleukin-6 and interleukin-8 levels in serum and synovial fluid of patients with osteoarthritis

Role of proinflammatory cytokines and chemokines in chronic arthropathy in CHIKV infection

Chikungunya virus (CHIKV) has caused large outbreaks worldwide in recent years. Acute-phase CHIKV infection has been reported to cause mild to severe febrile illness, and in some patients, this may be followed by long-lasting polyarthritis. The mainstay of treatment includes nonsteroidal anti-inflammatory drugs and other disease-modifying agents, the use of which is based on the assumption of an immunological interference mechanism in the pathogenesis. The present study has been designed to generate preliminary evidence to test this hypothesis. The levels of 30 cytokines were estimated in serum samples of acute CHIKV-infected patients, fully-recovered patients, patients with chronic CHIKV arthritis, and controls, using a quantitative multiplex bead ELISA. The levels of the proinflammatory cytokines IL-1 and IL-6 were elevated in acute patients, but IFN-γ/β and TNF-α levels remained stable. IL-10, which might have an anti-inflammatory effect, was also elevated, indicating a predominantly anti-inflammatory response in the acute phase of infection. Elevation of MCP-1, IL-6, IL-8, MIP-1α, and MIP-1β was most prominent in the chronic phase. These cytokines and chemokines have been shown to play important roles in other arthritides, including epidemic polyarthritis (EPA) caused by Ross River virus (RRV) and rheumatoid arthritis (RA).The immunopathogenesis of chronic CHIKV arthritis might have similarities to these arthritides. The novel intervention strategies being developed for EPA and RA, such as IL-6 and IL-8 signaling blockade, may also be considered for chronic CHIKV arthritis.

Adiponectin associates with markers of cartilage degradation in osteoarthritis and induces production of proinflammatory and catabolic factors through mitogen-activated protein kinase pathways

Introduction

Adiponectin is an adipokine that regulates energy metabolism and insulin sensitivity, but recent studies have pointed also to a role in inflammation and arthritis. The purpose of the present study was to investigate the association and effects of adiponectin on inflammation and cartilage destruction in osteoarthritis (OA).

Methods

Cartilage and blood samples were collected from 35 male OA patients undergoing total knee replacement surgery. Preoperative radiographs were evaluated using Ahlbäck classification criteria for knee OA. Circulating concentrations of adiponectin and biomarkers of OA, that is, cartilage oligomeric matrix protein (COMP) and matrix metalloproteinase 3 (MMP-3), were measured. Cartilage samples obtained at the time of surgery were cultured ex vivo, and the levels of adiponectin, nitric oxide (NO), IL-6, MMP-1 and MMP-3 were determined in the culture media. In addition, the effects of adiponectin on the production of NO, IL-6, MMP-1 and MMP-3 were studied in cartilage and in primary chondrocyte cultures.

Results

Plasma adiponectin levels and adiponectin released from OA cartilage were higher in patients with the radiologically most severe OA (Ahlbäck grades 4 and 5) than in patients with less severe disease (Ahlbäck grades 1 to 3). Plasma adiponectin concentrations correlated positively with biomarkers of OA, that is, COMP (r = 0.55, P = 0.001) and MMP-3 (r = 0.34, P = 0.046). Adiponectin was released by OA cartilage ex vivo, and it correlated positively with production of NO (r = 0.43, P = 0.012), IL-6 (r = 0.42, P = 0.018) and MMP-3 (r = 0.34, P = 0.051). Furthermore, adiponectin enhanced production of NO, IL-6, MMP-1 and MMP-3 in OA cartilage and in primary chondrocytes in vitro in a mitogen-activated protein kinase (MAPK)-dependent manner.

Conclusions

The findings of this study show that adiponectin is associated with, and possibly mediates, cartilage destruction in OA.

Oxidative stress in secondary osteoarthritis: from cartilage destruction to clinical presentation?

Due to an increasing life expectance, osteoarthritis (OA) is one of the most common chronic diseases. Although strong efforts have been made to regenerate degenerated joint cartilage, OA is a progressive and irreversible disease up to date. Among other factors the dysbalance between free radical burden and cellular scavenging mechanisms defined as oxidative stress is a relevant part of OA pathogenesis. Here, only little data are available about the mediation and interaction between different joint compartments. The article provides a review of the current literature regarding the influence of oxidative stress on cellular aging, senescence and apoptosis in different joint compartments (cartilage, synovial tissue and subchondral bone). Free radical exposure is known to promote cellular senescence and apoptosis. Radical oxygen species (ROS) involvement in inflammation, fibrosis control and pain nociception has been proven. The data from literature indicates a link between free radical burden and OA pathogenesis mediating local tissue reactions between the joint compartments. Hence, oxidative stress is likely not only to promote cartilage destruction but also to be involved in inflammative transformation, promoting the transition from clinically silent cartilage destruction to apparent OA. ROS induced by exogenous factors such as overload, trauma, local intraarticular lesion and consecutive synovial inflammation cause cartilage degradation. In the affected joint, free radicals mediate disease progression. The interrelationship between oxidative stress and OA etiology might provide a novel approach to the comprehension and therefore modification of disease progression and symptom control.

Physiology and pathophysiology of nitrosative and oxidative stress in osteoarthritic joint destruction

Osteoarthritis (OA) is one of the most common chronic diseases, with increasing importance due to increased life expectancy. On a cellular level, the pathophysiology of joint function impairment and ultimate destruction associated with OA remains poorly understood. Free radicals are highly reactive molecules involved in both normal intracellular signal transduction and degenerative cellular processes. An imbalance between the free radical burden and cellular scavenging mechanisms, defined as oxidative stress, has been identified as a relevant factor in OA pathogenesis. This literature review elucidates the involvement of nitrosative and oxidative stress in cellular ageing in joints, cell senescence, and apoptosis. Free radical exposure is known to promote cellular senescence and apoptosis, and the involvement of radical oxygen species (ROS) in inflammation, fibrosis control, and pain nociception has been proven. A relatively novel approach to OA pathophysiology considers the joint to be a dynamic system consisting of 3, continuously interacting compartments, cartilage, synovial tissue, and subchondral bone. Current knowledge concerning free radical involvement in paracrine signalling in OA is reviewed. The interrelationship between oxidative imbalances and OA pathophysiology may provide a novel approach to the comprehension, and therefore modification, of OA disease progression and symptom control.

Anti-inflammatory activity of monogalactosyldiacylglycerol in human articular cartilage in vitro: activation of an anti-inflammatory cyclooxygenase-2 (COX-2) pathway

Introduction

The mono- and digalactosyldiacylglycerol (MGDG and DGDG) galactolipids have been purified from the thermophilic blue-green alga Phormidium sp. ETS-05 that colonizes the therapeutic thermal mud of Abano Terme and Montegrotto Terme, Italy. Both compounds present a marked composition in polyunsaturated fatty acids, mainly omega-3. The therapeutic thermal mud is applied mainly to osteoarthritic cartilage patients. In the present study the effect of MGDG treatment on proteins and factors expressed by human articular cartilage cells in culture and on pathways activated in inflammatory conditions was studied.

Methods

Primary cultures of human articular chondrocytes were used at cell passage number 1 (P1). Cells were treated in serum-free medium with inflammatory cytokines in the presence and in the absence of MGDG. Western blot was performed on collected medium and on cell layers. At least three different experiments were performed on primary cultures. The quantitation of the MGDG effect was performed by densitometric scanning of Western blots. p38 Mitogen Activated Protein Kinase (p38) activation, Nuclear Factor-kappaB (NF-kB) activation and Prostaglandin E₂ (PGE₂) quantitation were performed by commercially available assays. Results are given as the mean values ± SD. All statistical analyses were performed using GraphPad software. The two-tailed Student's t -test was performed.

Results

We report that MGDG: 1) represses the expression of interleukin-6 (IL-6) and interleukin-8 (IL-8) induced by interleukin-1alpha (IL-1α) or IL-1α + tumor necrosis factor α (TNFα) interfering with the p38 and NF-kB pathways; 2) is not toxic for the cells and does not affect the cell phenotype; 3) strongly enhances COX-2 expression induced by IL-1α or IL-1α + TNFα; 4) represses mPGES expression induced by IL-1α and the synthesis of PGE₂ and induces the synthesis of 15-deoxy-Δ 12,14-prostaglandin J₂ (15ΔPGJ₂). In addition, the COX-2 product 15ΔPGJ₂ added to the cells: 1) strongly represses IL-6 and IL-8 induced by IL-1α; 2) represses mPGES expression induced by IL-1α and the synthesis of PGE₂.

Conclusions

All together these data suggest that MGDG has an anti-inflammatory activity in human articular cartilage and possibly activates an anti-inflammatory loop triggered by COX-2 via 15ΔPGJ₂ production, indicating a possible role of COX-2 in resolution of inflammation. The purified compound is a novel anti-inflammatory agent potentially active for human articular cartilage pathologies related to inflammation.

Bradykinin and B₂ receptor antagonism in rat and human articular chondrocytes

BACKGROUND AND PURPOSE

In osteoarthritis (OA), bradykinin (BK) is known to contribute to pain and synovitis, but not to cartilage degradation. Here, we investigated effects of BK and its antagonists on chondrocytes, cells involved in cartilage homeostasis.

EXPERIMENTAL APPROACH

BK receptor density and affinities of BK, its analogues and antagonists were measured in cultured human and rat chondrocytes by radioligand binding. Effects of BK were assessed by accumulation of inositol phosphates (IP) and release of interleukin (IL)-6 and IL-8.

KEY RESULTS

Density of [³H]-BK binding sites was higher (13-30-fold) and BK evoked a greater (48-fold) IP production, in human than in rat chondrocytes. The BK B₂ receptor antagonists MEN16132 and icatibant displayed similar binding affinity. MEN16132 was 40-fold more potent than icatibant in the IP assay. In human chondrocytes, BK increased release (over 24 h) of IL-6 and IL-8, effects blocked by MEN16132 but not by the B₁ receptor antagonist Lys-[Leu⁸][desArg⁹]BK. BK-induced release of IL-6, but not of IL-8, was partially inhibited by indomethacin (10 µM) and nordihydroguaiaretic acid (10 µM). Antagonists for the prostanoid EP receptors (AH6809 10 µM; L-798,196, 200 nM; L-161,982, 1 µM) were ineffective. Dexamethasone (100 nM) partially inhibited release of both IL-6 and IL-8. Inhibitors of intracellular downstream signalling pathways (SB203580 10 µM; PD98059, 30 µM; SP600125, 30 µM; BAY-117085, 5 µM) indicated the involvement of p38 MAPK and the activation of NF-κB.

CONCLUSION AND IMPLICATIONS

BK mediated inflammatory changes and cartilage degradation and B₂ receptor blockade would, therefore, be a potential treatment for OA.

Advanced glycation end products induce the expression of interleukin-6 and interleukin-8 by receptor for advanced glycation end product-mediated activation of mitogen-activated protein kinases and nuclear factor-κB in human osteoarthritis chondrocytes

OBJECTIVE

To investigate whether advanced glycation end products (AGEs) induce the expression of IL-6 and IL-8 through the receptor for AGEs (RAGE)-activated pathways in human OA chondrocytes.

METHODS

OA chondrocytes were stimulated with AGE-modified BSA (AGE-BSA). Gene expression of IL-6 and IL-8 was quantified by TaqMan assays and the production was determined using ELISAs. Immunoblotting was used to analyse the activation of mitogen-activated protein kinases (MAPKs) and the degradation of IκBα. Activation of NF-κB was determined using an ELISA. Pharmacological studies to elucidate the involved pathways were executed using transfection with small interfering RNAs (siRNAs), inhibitors of MAPKs and NF-κB.

RESULTS

AGE-BSA induced the expression of IL-6 and IL-8 in OA chondrocytes, which was inhibited by pre-treatment with soluble RAGE (sRAGE) or RAGE knockdown by siRNAs. Treatment with SB202190 (p38-MAPK inhibitor) or PD98059 (ERK inhibitor) inhibited AGE-BSA-induced IL-6 and IL-8 expression. However, SP600125 (JNK inhibitor) had no effect on AGE-BSA-induced IL-6 expression but inhibited the expression of IL-8. Treatment with NF-κB inhibitors suppressed AGE-BSA-induced IL-6 and IL-8 expression.

CONCLUSIONS

This is the first study to demonstrate that AGEs induce the expression of IL-6 and IL-8 in OA chondrocytes. A novel finding of our studies is that in OA chondrocytes, AGE-BSA-induced expression of IL-6, but not of IL-8, was independent of the JNK pathway. Activation of NF-κB was an absolute requirement for both IL-6 and IL-8 expression. These results demonstrate that AGE-BSA-induced expression of IL-6 and IL-8 via RAGE is mediated through different MAPK signalling pathways in OA and possibly in other degenerative diseases.

Role of proinflammatory cytokines in the pathophysiology of osteoarthritis

Osteoarthritis (OA) is associated with cartilage destruction, subchondral bone remodeling and inflammation of the synovial membrane, although the etiology and pathogenesis underlying this debilitating disease are poorly understood. Secreted inflammatory molecules, such as proinflammatory cytokines, are among the critical mediators of the disturbed processes implicated in OA pathophysiology. Interleukin (IL)-1β and tumor necrosis factor (TNF), in particular, control the degeneration of articular cartilage matrix, which makes them prime targets for therapeutic strategies. Animal studies provide support for this approach, although only a few clinical studies have investigated the efficacy of blocking these proinflammatory cytokines in the treatment of OA. Apart from IL-1β and TNF, several other cytokines including IL-6, IL-15, IL-17, IL-18, IL-21, leukemia inhibitory factor and IL-8 (a chemokine) have also been shown to be implicated in OA and could possibly be targeted therapeutically. This Review discusses the current knowledge regarding the role of proinflammatory cytokines in the pathophysiology of OA and addresses the potential of anticytokine therapy in the treatment of this disease.

A meta-analysis of interleukin-6 promoter polymorphisms on risk of hip and knee osteoarthritis

OBJECTIVE

Interleukin-6 is a pro-inflammatory cytokine involved in the pathogenesis of osteoarthritis (OA). We investigated the role of two single nucleotide polymorphisms (SNPs) mapping to the promoter of the IL-6 gene on genetic susceptibility to hip and knee OA.

METHODS

The -174G/C (rs1800795) and -597G/A (rs1800797) SNPs, implicated in the literature in risk of hip and hand OA, were genotyped in 2511 controls, 1101 hip OA cases and 1904 knee OA cases from four cohorts from the UK and Estonia. Data were analysed in conjuntion with published data on rs1800797 from the Genetics of OA and Lifestyle study (UK) on 791 controls, 1034 knee and 997 hip OA cases and rs1800795 data on 75 hip OA cases and 96 controls from Italy. Cases included both radiographic OA only and radiographic and symptomatic OA. Fixed and random-effects meta-analysis models were tested.

RESULTS

No significant association was found with hip OA or knee OA with either SNP nor with the haplotypes formed by them. For individual SNPs the smallest P-value for hip OA was observed using a random-effects model for rs1800795 OR(Gallele)=1.066 (95% CI 0.89-1.28) P<0.49, and significant heterogeneity between cohorts (I(2)=65%, P<0.034) was detected. For knee OA the smallest P-value was seen for rs1800797 OR(Aallele)=1.055 (95%CI 0.98-1.12) P<0.18, no significant heterogeneity was observed (I(2)=0%, P<0.68).

CONCLUSIONS

Our data do not support a role for the -174 and -597 IL-6 promoter polymorphisms in genetic susceptibility to knee or hip OA in Caucasian populations.

Joint aging and chondrocyte cell death

Articular cartilage extracellular matrix and cell function change with age and are considered to be the most important factors in the development and progression of osteoarthritis. The multifaceted nature of joint disease indicates that the contribution of cell death can be an important factor at early and late stages of osteoarthritis. Therefore, the pharmacologic inhibition of cell death is likely to be clinically valuable at any stage of the disease. In this article, we will discuss the close association between diverse changes in cartilage aging, how altered conditions influence chondrocyte death, and the implications of preventing cell loss to retard osteoarthritis progression and preserve tissue homeostasis.

Elevated osteopontin level of synovial fluid and articular cartilage is associated with disease severity in knee osteoarthritis patients

OBJECTIVE

To investigate osteopontin (OPN) levels in both synovial fluid and articular cartilage of patients with primary knee osteoarthritis (OA) and their relationship with severity of the disease.

METHOD

Fifty patients aged 48-81 years with knee OA and 10 healthy controls were enrolled in this study. Anteroposterior knee radiographs or/and Mankin score were taken to determine the disease severity of the affected knee. The radiographic grading of OA in the knee was performed by using the Kellgren-Lawrence criteria. OPN levels in synovial fluid were measured using enzyme-linked immunosorbent assay. OPN levels in articular cartilage were assessed by immunohistochemical methods.

RESULTS

Compared to healthy controls, OA patients had higher OPN concentration in synovial fluid (4519.60+/-1830.37, 95%CI 3999.42-5039.79 vs 1179.70+/-303.39, 95%CI 1035.53-1438.74 pg/ml, P<0.001)and articular cartilage(0.6+/-0.06, 95%CI 0.59-0.62 vs 0.43+/-0.07, 95%CI 0.38-0.48, P<0.01). In addition, synovial fluid OPN levels showed a positive correlation with articular cartilage OPN levels (r=0.411, 95%CI 0.150-0.619, P=0.003). Subsequent analysis showed that synovial fluid OPN levels significantly correlated with severity of disease (Spearman's rho=0.581, 95%CI 0.335-0.726, P<0.001). Furthermore, the articular cartilage levels of OPN also correlated with disease severity (Spearman's rho=0.675, 95%CI 0.500-0.808, P<0.001).

CONCLUSIONS

OPN in synovial fluid and articular cartilage is associated with progressive joint damage and is likely to be a useful biomarker for determining disease severity and progression in knee OA.

Serum chemokines in patients with rheumatoid arthritis treated with etanercept

Chemokines promote leucocyte traffic into the synovium, leading to the initiation and progression of the rheumatoid arthritis (RA). The aim of the study was to determine the effects of etanercept, a soluble tumour necrosis factor receptor (sTNFr), on the serum chemokines levels in patients with active RA. Patients were treated with 50 mg of subcutaneous injection of etanercept per week and methotrexate (10-25 mg/week). Serum levels of interleukin-8 (IL-8), RANTES (regulated upon activation, normal T cell expressed and secreted) and monocyte chemoattractant protein-1 (MCP-1) were assessed by ELISA at months 0, 3, 6, 9 and 12, prior to injection. 3-month treatment with etanercept diminished serum concentrations of IL-8, RANTES and MCP-1 (P < 0.05, P < 0.01 and P < 0.001, respectively). Subsequent etanercept administrations prolonged decrease in serum chemokines levels and in the case of IL-8 even intensified the reduction of its concentration in serum. These changes were accompanied by significant decrease of disease activity score (DAS28) (in all cases P < 0.001). Prior to the first etanercept administration, serum concentrations of studied chemokines correlated with markers of RA activity such as the erythrocyte sedimentation rate (ESR) and DAS28. Following next drug injection such associations were less or not significant. Therapy with etanercept and MTX not only caused a clinical improvement but also diminished serum chemokines levels in RA patients. Further treatment with etanercept sustained chemokines suppression.

Desirable effect of combination therapy with high molecular weight hyaluronate and NSAIDs on MMP production

OBJECTIVE

We previously reported that nonsteroidal anti-inflammatory drugs (NSAIDs) aggravated cartilage degeneration and that hyaluronate (HA) reversed the cartilage destruction accelerated by NSAIDs in a rabbit osteoarthritis (OA) model. In the present study, we analyzed the mechanisms of these effects of NSAIDs and HA.

METHOD

An experimental rabbit model of OA was induced by partial meniscectomy and treated with NSAIDs, HA and the combination of NSAIDs and HA over 2 weeks. After sacrifice, cartilage degeneration and the levels of matrix metalloproteases (MMP)-1, MMP-3 and MMP-13 in synovial lavage fluid were measured. In an in vitro study, human articular chondrocytes were cultured with NSAIDs and HA in the presence of interleukin (IL)-1beta or IL-6+sIL-6 for 24 h. After culture, the production of MMPs, IL-1beta, and IL-6 was measured.

RESULTS

The levels of MMP-1, MMP-3 and MMP-13 in synovial fluid from the NSAID-treated group were significantly higher than in controls. The increased production of MMPs induced by NSAIDs was counteracted by the concomitant administration of HA. In vitro studies showed that NSAIDs augmented IL-1beta- and IL-6-induced production of MMPs from human chondrocytes, while completely inhibiting the IL-1beta- and IL-6/sIL-6R-induced production of prostaglandin E(2) (PGE(2)). The addition of PGE(2) did not reduce the augmentation of MMP production. HA inhibited the promotion of cytokine-induced MMP and cytokine production by NSAIDs.

CONCLUSIONS

Our data clearly showed that HA inhibited NSAID-accelerated MMP production which was followed by inflammatory cytokine production from cytokine-activated chondrocytes. The results warrant further evaluation of the potential chondroprotective effects of co-administration of HA with NSAIDs.

Leptin enhances synthesis of proinflammatory mediators in human osteoarthritic cartilage--mediator role of NO in leptin-induced PGE2, IL-6, and IL-8 production

Obesity is an important risk factor for osteoarthritis (OA) in weight-bearing joints, but also in hand joints, pointing to an obesity-related metabolic factor that influences on the pathogenesis of OA. Leptin is an adipokine regulating energy balance, and it has recently been related also to arthritis and inflammation as a proinflammatory factor. In the present paper, the effects of leptin on human OA cartilage were studied. Leptin alone or in combination with IL-1 enhanced the expression of iNOS and COX-2, and production of NO, PGE₂, IL-6, and IL-8. The results suggest that the effects of leptin are mediated through activation of transcription factor nuclear factor κB (NF-κB) and mitogen-activated protein kinase (MAPK) pathway c-Jun NH₂-terminal kinase (JNK). Interestingly, inhibition of leptin-induced NO production with a selective iNOS inhibitor 1400 W inhibited also the production of IL-6, IL-8, and PGE₂, and this was reversed by exogenously added NO-donor SNAP, suggesting that the effects of leptin on IL-6, IL-8, and PGE₂ production are dependent on NO. These findings support the idea of leptin as a factor enhancing the production of proinflammatory factors in OA cartilage and as an agent contributing to the obesity-associated increased risk for osteoarthritis.

Curcumin inhibits pro-inflammatory mediators and metalloproteinase-3 production by chondrocytes

OBJECTIVE AND DESIGN

This study aims to investigate the effects of curcumin (Cur) on the extracellular matrix protein metabolism of articular chondrocytes and on their production of inflammatory mediators.

METHODS

Human chondrocytes in alginate beads and human cartilage explants were cultured in the absence or in the presence of interleukin (IL)-1beta (10(-11) M) and with or without Cur (5-20 microM). Nitric oxide (NO) synthesis was measured by the Griess spectrophotometric method; prostaglandin (PG) E(2) by a specific radioimmunoassay; and IL-6, IL-8, aggrecan (Agg), matrix metalloproteinase (MMP)-3, and tissue inhibitor of metalloproteinase (TIMP)-1 by specific enzyme-amplified immunoassays. Proteoglycan degradation was evaluated by the release of (35)S-glycosaminoglycans (GAG) from human cartilage explants.

RESULTS

In alginate beads and cartilage explant models, Cur inhibited the basal and the IL-1beta-stimulated NO, PGE(2), IL-6, IL-8, and MMP-3 production by human chondrocytes in a concentration-dependent manner. The TIMP-1 and the Agg productions were not modified. In the basal condition, (35)S-GAG release from cartilage explants was decreased by Cur.

CONCLUSIONS

Curcumin was a potent inhibitor of the production of inflammatory and catabolic mediators by chondrocytes, suggesting that this natural compound could be efficient in the treatment of osteoarthritis.

Discoidin domain receptor 2 mediates the collagen II-dependent release of interleukin-6 in primary human chondrocytes

We deciphered constituent parts of a signal transduction cascade that is initiated by collagen II and results in the release of various pro-inflammatory cytokines, including interleukin-6 (IL-6), in primary human chondrocytes. This cascade represents a feed-forward mechanism whereby cartilage matrix degradation is exacerbated by the mutually inducing effect of released collagen II fragments and pro-inflammatory cytokines. We previously proposed discoidin domain receptor 2 as a central mediator in this event. Since this cascade plays a prominent role in the pathogenesis of osteoarthritis, our study further investigates the hypothesis that discoidin domain receptor 2 is a candidate receptor for collagen II, and that transcription factor NFkappaB, lipid kinase PI3K, and the MAP kinases are constituent parts of this very signal transduction cascade. To accomplish this, we selectively knocked down the molecules of interest in primary human chondrocytes, induced the specified cascade by incubating primary human chondrocytes with collagen II, and observed the outcome, specifically the changes in interleukin-6 release. Knockdown was performed by siRNA-mediated gene silencing in the case of discoidin domain receptor 2 (DDR2) or by using specific inhibitors for the remainder of the molecules. Results indicated that discoidin domain receptor 2 mediates the collagen II-dependent release of interleukin-6 in primary human chondrocytes and that MAP kinases p38, JNK and ERK, as well as transcription factor NFkappaB, are integral components of intracellular collagen II signalling. Given the detrimental role of these molecules in osteoarthritis, our findings provide new targets for more specific therapeutics, which may have fewer side effects than those currently applied.

Relationship of plasma and synovial fluid BMP-7 with disease severity in knee osteoarthritis patients: a pilot study

The objective of this study was to investigate bone morphogenetic protein-7 (BMP-7) levels in both plasma and synovial fluid of patients with primary knee osteoarthritis (OA) and to determine their relationship to disease severity. Thirty-two patients with knee OA and 15 healthy subjects were enrolled in the study. Anteroposterior knee radiographs were taken to determine the disease severity of the affected knee. The radiographic grading of OA in the knee was performed using the Kellgren-Lawrence criteria. BMP-7 levels in the plasma and synovial fluid were measured using enzyme-linked immunosorbent assay. The mean plasma BMP-7 concentration of the knee OA patients was significantly higher compared with that of healthy controls (12.1 +/- 1.6 vs 3.5 +/- 0.9 pg/ml, P = 0.001). Although BMP-7 levels in plasma were higher with respect to paired synovial fluid samples, the difference was not statistically significant (12.1 +/- 1.6 vs 10.5 +/- 2.2 pg/ml, P = 0.3). Subsequent analysis showed that plasma BMP-7 levels significantly correlated with disease severity (r = 0.77, P < 0.001). Furthermore, the synovial fluid levels of BMP-7 also correlated with disease severity (r = 0.60, P < 0.001). In addition, plasma BMP-7 levels showed a positive correlation with synovial fluid BMP-7 levels (r = 0.71, P < 0.001). Overexpression of BMP-7 in plasma and synovial fluid is related to progressive joint damage in knee OA. These findings suggest that BMP-7 might serve as a biochemical parameter for determining disease severity in primary knee OA and could play a potential role in cartilage protection and repair of OA.

Correlation of plasma and synovial fluid osteopontin with disease severity in knee osteoarthritis

OBJECTIVES

The purposes of this study were to examine osteopontin levels in both plasma and synovial fluid of patients with primary knee osteoarthritis (OA) and to investigate their relationship with severity of the disease.

DESIGN AND METHODS

Thirty-two patients aged 53-83 years with knee OA and 15 healthy controls were enrolled in this study. Anteroposterior knee radiographs were taken to determine the disease severity of the affected knee. The radiographic grading of OA in the knee was performed by using the Kellgren-Lawrence criteria. Osteopontin levels in the plasma and synovial fluid were measured using enzyme-linked immunosorbent assay.

RESULTS

The mean plasma osteopontin concentration of the knee OA patients was significantly higher compared with that of healthy controls (168.8+/-15.6 vs 67.2+/-7.7 ng/mL, P<0.0001). Osteopontin levels in synovial fluid were significantly higher with respect to paired plasma samples (272.1+/-15.0 vs 168.8+/-15.6 ng/mL, P<0.001). In addition, plasma osteopontin levels showed a positive correlation with synovial fluid osteopontin levels (r=0.373, P=0.035). Subsequent analysis showed that plasma osteopontin levels significantly correlated with severity of disease (r=0.592, P<0.001). Furthermore, the synovial fluid levels of osteopontin also correlated with disease severity (r=0.451, P=0.01).

CONCLUSION

The data suggest that osteopontin in plasma and synovial fluid is related to progressive joint damage in knee OA. Osteopontin may serve as a biochemical marker for determining disease severity and could be predictive of prognosis with respect to the progression of knee OA.

Inflammatory response in patients with active and inactive osteoarthritis

In the present study, we have investigated comparatively the inflammatory response of patients with active and inactive osteoarthritis. The sera from 31 healthy individuals, 37 patients with active OA, and 19 patients with inactive OA were assayed for TNF-alpha, IL-6, sRANKL, RANTES, and MRP8 using ELISA in order to evaluate their potential as markers of disease activity. Also, the spontaneous and LSP-induced release of TNF-alpha and IL-6 by peripheral blood neutrophils was determined. The activation of OA is associated with elevated TNF-alpha, IL-6, and RANTES serum levels while sRANKL and MRP8 appeared to be increased in both active and inactive OA. The neutrophil spontaneous and up-regulated by LPS cytokine release can contribute to the exacerbation of OA.

Osteoblasts derived from osteophytes produce interleukin-6, interleukin-8, and matrix metalloproteinase-13 in osteoarthritis

To clarify the significance of the osteophytes that appear during the progression of osteoarthritis (OA), we investigated the expression of inflammatory cytokines and proteases in osteoblasts from osteophytes. We also examined the influence of mechanical stress loading on osteoblasts on the expression of inflammatory cytokines and proteases. Osteoblasts were isolated from osteophytes in 19 patients diagnosed with knee OA and from subchondral bone in 4 patients diagnosed with femoral neck fracture. Messenger RNA expression and protein production of inflammatory cytokines and proteases were analyzed using real-time RT-PCR and ELISA, respectively. To examine the effects of mechanical loading, continuous hydrostatic pressure was applied to the osteoblasts. We determined the mRNA expression and protein production of IL-6, IL-8, and MMP-13, which are involved in the progression of OA, were increased in the osteophytes. Additionally, when OA pathological conditions were simulated by applying a nonphysiological mechanical stress load, the gene expression of IL-6 and IL-8 increased. Our results suggested that nonphysiological mechanical stress may induce the expression of biological factors in the osteophytes and is involved in OA progression. By controlling the expression of these genes in the osteophytes, the progression of cartilage degeneration in OA may be reduced, suggesting a new treatment strategy for OA.

Joint fluid antioxidants are decreased in osteoarthritic joints compared to joints with macroscopically intact cartilage and subacute injury

OBJECTIVE

Excess reactive oxygen species and oxidative damage have been associated with the pathogenesis of osteoarthritis (OA). Extracellular superoxide dismutase (EC-SOD or SOD3) scavenges superoxide is the major catalytic antioxidant in joint fluid and is decreased in OA cartilage. We studied human joint fluid samples to test whether there is an association between OA and EC-SOD or other low molecular antioxidants in the joint fluid.

METHODS

Joint fluid samples were obtained from 28 subjects with severe OA undergoing arthrocentesis or knee joint replacement and compared to joint fluid from 12 subjects undergoing knee arthroscopy for chronic knee pain, meniscal tears or anterior cruciate ligament reconstruction. EC-SOD protein was assayed by enzyme-linked immunosorbent assay (ELISA). Ascorbate and urate were measured with high performance liquid chromatography (HPLC) and total nitrates by the Greiss reaction. Glutathione (GSH) and oxidized glutathione were measured using a colorimetric method. Interleukin-6 (IL-6) and transforming growth factor-beta (TGF-beta) were both measured with ELISA.

RESULTS

Human joint fluid contains significant amounts of the extracellular, catalytic antioxidant EC-SOD. Joint fluid from OA subjects is characterized by significantly decreased EC-SOD levels and significant decreases in GSH, and ascorbate compared to the reference group of knee joints with pain or subacute injury but macroscopically intact cartilage. GSH and ascorbate show only an age effect with no effect from disease state on regression modeling. Urate is present in joint fluid but does not show a significant difference between groups. IL-6 and TGF-beta both show non-significant trends to increases in the arthritic subjects. There was no correlation of EC-SOD levels with IL-6 as a marker of inflammation in either the comparison group or the OA group.

CONCLUSIONS

EC-SOD, the major scavenger of reactive oxygen species (ROS) in extracellular spaces and fluids, is decreased in late stage OA joint fluid compared to fluid from injured/painful joints with intact cartilage. Injured joints may be able to increase or maintain secretion of EC-SOD but it appears that late stage OA joints fail to do so in spite of increased oxidative stress seen in the disease. Associated age related declines in GSH and ascorbate might also contribute to the development of severe OA. The net effect of these changes in joint fluid antioxidants is likely to accelerate the damaging oxidant effects on extracellular matrix stability in cartilage tissue.

Common interleukin-6 promoter variants associate with the more severe forms of distal interphalangeal osteoarthritis

Introduction

The objective of this study was to investigate the relationship of the IL-6 promoter variants G-597A, G-572C and G-174C (rs1800797, rs1800796 and rs1800795, respectively), which have been shown to affect both the transcription and secretion of IL-6, to symptomatic distal interphalangeal (DIP) osteoarthritis (OA).

Methods

A total of 535 women aged 45 to 63 years were included. Radiographs of both hands were taken and each DIP joint was evaluated (grade 0 to 4) for the presence of OA. Information on symptoms (pain, tenderness) in each joint was collected by using a self-administered questionnaire. Symptomatic DIP OA was defined by the presence of both radiographic findings of grade 2 or more and symptoms in at least two DIP joints, and symmetrical DIP OA by the presence of radiographic findings of grade 2 or more in at least one symmetrical pair of DIP joints. Common polymorphic loci in the IL-6 gene were amplified and the promoter haplotypes were reconstructed from genotype data with the PHASE program. Logistic regression analysis was used to examine the association between the IL-6 genotypes/diplotypes and the DIP OA outcome.

Results

The G alleles of two promoter single nucleotide polymorphisms (SNPs) G-597A and G-174C were more common among the subjects with symptomatic DIP OA than among those with no disease (P = 0.020 and 0.024, corrected for multiple testing). In addition, the carriage of at least one G allele in these positions increased the risk of disease (P = 0.006 and P = 0.008, respectively). Carrying a haplotype with the G allele in all three promoter SNPs increased the risk of symptomatic DIP OA more than fourfold (odds ratio (OR) 4.45, P = 0.001). Carriage of the G-G diplotype indicated an increased risk of both symmetrical DIP OA (OR 1.52, 95% confidence interval 1.01 to 2.28) and symptomatic DIP OA (OR 3.67, 95% confidence interval 1.50 to 9.00).

Conclusion

The present study showed that the presence of G alleles at common IL-6 polymorphic promoter loci was associated with the more severe DIP OA outcomes, symmetrical and symptomatic.

Interleukin-6 (IL-6) and/or soluble IL-6 receptor down-regulation of human type II collagen gene expression in articular chondrocytes requires a decrease of Sp1.Sp3 ratio and of the binding activity of both factors to the COL2A1 promoter

Type II collagen is composed of alpha1(II) chains encoded by the COL2A1 gene. Alteration of this cartilage marker is a common feature of osteoarthritis. Interleukin-6 (IL-6) is a pro-inflammatory cytokine that needs a soluble form of receptor called sIL-6R to exert its effects in some cellular models. In that case, sIL-6R exerts agonistic action. This mechanism can make up for the partial or total absence of membrane-anchored IL-6 receptors in some cell types, such as chondrocytes. Our study shows that IL-6, sIL-6R, or both inhibit type II collagen production by rabbit articular chondrocytes through a transcriptional control. The cytokine and/or sIL-6R repress COL2A1 transcription by a -63/-35 sequence that binds Sp1.Sp3. Indeed, IL-6 and/or sIL-6R inhibit Sp1 and Sp3 expression and their binding activity to the 63-bp promoter. In chromatin immunoprecipitation experiments, IL-6.sIL-6R induced an increase in Sp3 recruitment to the detriment of Sp1. Knockdown of Sp1.Sp3 by small interference RNA and decoy strategies were found to prevent the IL-6- and/or sIL-6R-induced inhibition of COL2A1 transcription, indicating that each of these Sp proteins is required for down-regulation of the target gene and that a heterotypic Sp1.Sp3 complex is involved. Additionally, Sp1 was shown to interact with Sp3 and HDAC1. Indeed, overexpression of a full-length Sp3 cDNA blocked the Sp1 up-regulation of the 63-bp COL2A1 promoter activity, and by itself, inhibits COL2A1 transcription. We can conclude that IL-6, sIL-6R, or both in combination decrease both the Sp1.Sp3 ratio and DNA-binding activities, thus inhibiting COL2A1 transcription.

Effects of nimesulide on pain and on synovial fluid concentrations of substance P, interleukin-6 and interleukin-8 in patients with knee osteoarthritis: comparison with celecoxib

OBJECTIVE

This study was designed to investigate the analgesic effects of nimesulide and celecoxib in patients with knee osteoarthritis (OA). In patients with joint effusion, the effects of these non-steroidal anti-inflammatory drugs (NSAIDs) on synovial fluid concentrations of substance P (SP), interleukin (IL)-6 and IL-8 also were evaluated.

METHODS

Patients were randomly assigned either nimesulide (100 mg twice a day) or celecoxib (200 mg once a day) for 2 weeks. The intensity of joint pain was assessed with a 100-mm visual analogue scale (VAS). Furthermore, patients completed questions about analgesic efficacy and overall tolerability of the treatments on a five-point categorical scale. Synovial fluid samples were drawn at baseline, 30 min after the first drug intake (day 1), and 30 min after the last drug intake (day 14).

RESULTS

We enrolled 44 patients, 20 of whom had a joint effusion. In this group, the effects of nimesulide were more marked than for celecoxib, with evidence of a faster onset of the analgesic action. Both after a single or repeated administration, nimesulide significantly reduced the synovial fluid concentrations of SP and IL-6. Celecoxib, on the other hand, did not change the concentrations of SP and significantly reduced the levels of IL-6 only on day 14. None of the drugs affected IL-8. Both drugs were generally well tolerated.

CONCLUSIONS

These results provide evidence that nimesulide is an effective agent for the symptomatic treatment of OA. The effect on inflammatory pain mediators is consistent with the fast analgesic action of this NSAID.

Elevated IL-6 levels in the synovial fluid of osteoarthritis patients stem from plasma cells

OBJECTIVE

To analyse the levels of interleukin-6 (IL-6) in the synovial fluids and sera of patients with osteoarthritis (OA) and to identify the IL-6-secreting cells.

METHODS

Serum, synovial fluid, synovial tissue, and articular cartilage samples were collected from 49 OA patients with end-stage knee or hip OA who underwent joint replacement surgery. Serum and synovial fluid levels of IL-6 were measured by enzyme-linked immunosorbent assay (ELISA) and IL-6-secreting cells were identified by immunohistochemistry.

RESULTS

Eight out of 49 patients (16%) exhibited elevated IL-6 levels in the synovial fluids, averaging at 2022+/-526 pg/mL, while the levels in the rest of the patients averaged at 132+/-19 pg/mL. The sera levels of all patients were comparable in the 10 pg/mL range. Immunohistochemical analyses revealed plasma cells in the synovial lining of the high producers as the source of IL-6.

CONCLUSIONS

Synovial fluid IL-6 levels may help to classify OA patients and may point to a subgroup with a particular impact from their immune system.

Prospects for disease modification in osteoarthritis

Osteoarthritis (OA) can be a progressive, disabling disease, leading to diminished quality of life, and, for over 500,000 individuals annually in the US, total joint replacement. The etiology of OA will vary among individuals, with potential roles for systemic factors (such as genetics and obesity) as well as for local biomechanical factors (such as muscle weakness, joint laxity and traumatic injury). Joint deterioration occurs over extended periods of time, and the diverse molecular mechanisms that mediate pathogenic events of early, mid and late disease are not yet fully understood. The success of biologic therapies in the treatment of rheumatoid arthritis has demonstrated that the blockade of a single dominant cytokine or regulatory molecule can prevent cartilage destruction in a complex disease, and has raised expectations that mechanism-based treatments could also be developed for patients with OA. In this review, we will address the biological mechanisms that mediate structural damage in OA and examine current targets that are candidates for disease modification. The challenges to drug development and the obstacles to disease modification strategies will also be addressed.

Consequences of mutations in the non-coding RMRP RNA in cartilage-hair hypoplasia

Cartilage-hair hypoplasia (CHH), also known as metaphyseal chondrodysplasia McKusick type (OMIM no. 250250), is an autosomal recessive, multi-systemic disease characterized by disproportionate short stature, fine and sparse hair, deficient cellular immunity and a predisposition to malignancy. It is caused by mutations in RMRP, the RNA component of the ribonucleoprotein complex RNase MRP, and, thus, CHH represents one of few Mendelian disorders caused by mutations in a nuclear encoded, non-coding RNA. While studies in yeast indicate that RMRP contributes to diverse cellular functions, the pathogenesis of the human condition is unknown. Studies of our CHH patient cohort revealed mutations in both the promoter and the transcribed region of RMRP. While mutations in the promoter abolished transcription in vitro, RMRP RNA levels in patients with transcribed mutations were also decreased suggesting an unstable RNA. RMRP mutations introduced into the yeast ortholog, NME1, exhibited normal mitochondrial function, chromosomal segregation and cell cycle progression, while a CHH fibroblast cell line exhibited normal mitochondrial content. However, the most commonly found mutation in CHH patients, 70A>G, caused an alteration in ribosomal processing by altering the ratio of the short versus the long form of the 5.8S rRNA in yeast. Transcriptional profiling of CHH patient RNAs showed upregulation of several cytokines and cell cycle regulatory genes, one of which has been implicated in chondrocyte hypertrophy. These data suggest that alteration of ribosomal processing in CHH is associated with altered cytokine signalling and cell cycle progression in terminally differentiating cells in the lymphocytic and chondrocytic cell lineages.

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

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

Macrophage-like synoviocytes display phenotypic polymorphisms in a serum-free tissue-culture medium

Synovial macrophages play an outstanding role in many rheumatic diseases. However, traditional serum-containing tissue-culture techniques hamper in vitro studies due to fibroblast activation not found in vivo. The objective of this study was to examine dissociated synovial cells in a macrophage-selective, serum-free tissue-culture medium. Osteoarthritis synovial tissue (n=11) was cultured in Iscove's Modified Dulbecco's Medium (IMDM) with 10% fetal bovine serum (FBS) and compared to a serum-free, insulin-supplemented medium. After 9-11 and 19-21 days in vitro, immunohistochemistry was performed for macrophage/lymphocyte markers and cell division. Cytokine profiles were determined by RT-PCR. In serum, cells with a bipolar morphology rapidly proliferated. Respectively, 14.34+/-12.94% and 13.25+/-12.66% expressed CD68 and HLA-DR. These markers further decreased after one passage. In serum-free medium, proliferation was infrequent, and cells with diverse morphologies expressed 83.10+/-6.80% and 55.03+/-6.88% CD68 and HLA-DR respectively. CD14 was rare, and lymphocytes were missing. Both cultures expressed interleukin-6 and interleukin-8. This novel serum-free method permits the culture of distinct CD68/HLA-DR associated phenotypes.

Different ELR (+) angiogenic CXC chemokine profiles in synovial fluid of patients with Behçet's disease, familial Mediterranean fever, rheumatoid arthritis, and osteoarthritis

The aim of the present study was to determine synovial levels of ELR (+) CXC chemokines, known to attract mainly neutrophils to inflamed tissues by binding the neutrophil chemokine receptors CXCR1 and CXCR2 and promoting neovascularization in patients with various inflammatory disorders. The study group consisted of 14 patients with Behçet's disease and nine with familial Mediterranean fever. Fourteen patients with rheumatoid arthritis and 16 with osteoarthritis served as controls. Synovial chemokine levels were measured by two-step sandwich enzyme-linked immunosorbent assay, and significant differences were found in the various chemokines studied. In addition to its angiogenic properties, increased synovial levels of interleukin-8 by attraction of more neutrophils to synovial fluids might also be responsible for the acute synovitis in patients with Behçet's disease. However, the absence of chronic changes with the eventual development of pannus and erosions might result from relatively lower expression of interleukin-8 and the transient, short-lived nature of the arthritis observed in these patients.

Cytokines as therapeutic targets for osteoarthritis

Osteoarthritis (OA) is a debilitating, progressive disease of diarthrodial joints associated with the aging process. With the exception of anti-inflammatory corticosteroids and nonsteroidal anti-inflammatory drugs which inhibit cyclo-oxygenase-2, the enzyme responsible for prostaglandin biosynthesis in inflammation, no specific therapy based on fundamental intracellular pathways of chondrocytes and synoviocytes exists for the medical management of OA. At the molecular level, OA is characterized by an imbalance between chondrocyte anabolism and catabolism. Disruption of chondrocyte homeostasis primarily affects the cartilage extracellular matrix (ECM), which is responsible for the biomechanical properties of the tissue. Recent evidence has implicated cytokines, among which interleukin (IL)-1, tumor necrosis factor-alpha, IL-6, and IL-17 seem most involved in the OA process of cartilage destruction. The primary role of these cytokines is to modulate the expression of matrix metalloproteinases and cartilage ECM proteins. Cartilage repair that could restore the functional integrity of the joint is also impaired because chondrocytes in OA cartilage appear unable to respond to insulin-like growth factor-1 or respond abnormally to transforming growth factor-beta. As these growth factors also modulate cytokine expression, they may prove useful in designing strategies for suppressing 'chondrocyte activation'. Although cytokines and growth factors provide a potential therapeutic target for OA, it will be necessary to elucidate the fundamental mechanisms that cytokines employ to cause chondrocyte and synoviocyte dysfunction before 'anti-cytokine' therapy can be employed in the medical management of the disease.

Synovial response to intraarticular injections of hyaluronate in frozen shoulder: a quantitative assessment with dynamic magnetic resonance imaging

To clarify the response of frozen shoulder (FS) to intraarticular injections of high-molecular-weight sodium hyaluronate (HA), a mixture of 2.5 ml of HA and 1.5 ml of 1% lidocaine was injected into the glenohumeral joint of 11 patients with FS, 8 of whom received five weekly injections. The patients were assessed using the Japanese Orthopaedic Association shoulder score (JOA score) before the first injection, 1 week after the first injection, and 1 week after the final injection. Following each clinical evaluation, the patients underwent dynamic magnetic resonance imaging enhanced with Gd-DTPA, and the coefficient of enhancement (CE) in the glenohumeral synovium was calculated, with the examiners blinded to the clinical information. The JOA score tended to be greater and the CE smaller after injection than before injection. The changes in the CE following both single and repeated injections were negatively correlated with changes in the JOA score. Thus, clinical improvement in patients with FS was associated with a decrease in the CE. Because the CE depends on the degree of synovitis, the therapeutic effect of intraarticular HA injection for FS results, at least in part, from suppression of synovitis in the glenohumeral joint through an antiinflammatory effect.

Does hyaluronan affect inflammatory cytokines in knee osteoarthritis?

Our aim was to investigate the effects of hyaluronan on inflammatory cytokines in the synovial fluid of patients with knee osteoarthritis. The study was single blind, placebo-controlled, and randomized. We administered hyaluronan to 22 patients in the study group and placebo to 19 in the control group. Enzyme-linked immunosorbent assay was used to determine the levels of cytokines. Both HA and placebo caused a significant decrease in interleukin (IL)-6 levels (P=0.0001 and P=0.04, respectively). But it was more significant in the study group. However, IL-8 and tumor necrosis factor alpha (TNF-alpha) levels did not change in either group (P>0.05). The amount of effusion decreased significantly in the study group (P=0.001) but not in the control group (P=0.133). It can be concluded that hyaluronan considerably decreased IL-6 levels, which correlated with clinical improvement, but had no effect on IL-8 and TNF-alpha levels in synovial fluid. However, larger studies with longer follow-up periods are needed to explain the effect of hyaluronan on cytokines.

IL-8/CXCL8 and growth-related oncogene alpha/CXCL1 induce chondrocyte hypertrophic differentiation

Foci of chondrocyte hypertrophy that commonly develop in osteoarthritic (OA) cartilage can promote dysregulated matrix repair and pathologic calcification in OA. The closely related chemokines IL-8/CXCL8 and growth-related oncogene alpha (GROalpha)/CXCL1 and their receptors are up-regulated in OA cartilage chondrocytes. Because these chemokines regulate leukocyte activation through p38 mitogen-activated protein kinase signaling, a pathway implicated in chondrocyte hypertrophic differentiation, we tested whether IL-8 and GROalpha promote chondrocyte hypertrophy. We observed that normal human and bovine primary articular chondrocytes expressed both IL-8Rs (CXCR1, CXCR2). IL-8 and the selective CXCR2 ligand GROalpha (10 ng/ml) induced tissue inhibitor of metalloproteinase-3 expression, markers of hypertrophy (type X collagen and MMP-13 expression, alkaline phosphatase activity), as well as matrix calcification. IL-8 and the selective CXCR2 ligand GROalpha also induced increased transamidation activity of chondrocyte transglutaminases (TGs), enzymes up-regulated in chondrocyte hypertrophy that have the potential to modulate differentiation and calcification. Under these conditions, p38 mitogen-activated protein kinase pathway signaling mediated induction of both type X collagen and TG activity. Studies using mouse knee chondrocytes lacking one of the two known articular chondrocyte-expressed TG isoenzymes (TG2) demonstrated that TG2 was essential for murine GROalpha homologue KC-induced TG activity and critically mediated induction by KC of type X collagen, matrix metalloproteinase-13, alkaline phosphatase, and calcification. In conclusion, IL-8 and GROalpha induce articular chondrocyte hypertrophy and calcification through p38 and TG2. Our results suggest a novel linkage between inflammation and altered differentiation of articular chondrocytes. Furthermore, CXCR2 and TG2 may be sites for intervention in the pathogenesis of OA.

Effects of tramadol on synovial fluid concentrations of substance P and interleukin-6 in patients with knee osteoarthritis: comparison with paracetamol

Both the analgesic drugs tramadol and paracetamol are widely used for the symptomatic therapy of osteoarthritis (OA). The aim of this double-blind, randomised study in patients with knee OA was to compare their effects on synovial fluid concentrations of interleukin (IL)-6 and substance P (SP). Moreover, we evaluated plasma and synovial fluid concentrations of tramadol and its active metabolite (O-desmethyl-tramadol, M1) after oral treatment with this drug. Twenty patients were enrolled. A group of 10 patients received tramadol (50 mg three times a day), and another group of 10 patients were treated with paracetamol (500 mg three times a day) for 7 days. Both drugs significantly reduced the intensity of joint pain. The synovial fluid concentrations of SP were significantly reduced only by the treatment with tramadol. In this group of patients, IL-6 synovial fluid concentrations were slightly, but not significantly, decreased. Paracetamol did not significantly change the synovial fluid concentrations of SP and IL-6. After oral administration, a considerable amount of tramadol was measurable in synovial fluid. Both in plasma and synovial fluid the concentrations of M1 were markedly lower than those of tramadol, with a T/M1 ratio of 14.7+/-4.6 and 9.3+/-3.9, respectively. These data demonstrate that the activity of tramadol may involve the modulation of inflammatory mediators. Moreover, they indicate that after oral treatment with tramadol, both the parent drug and its active metabolite can penetrate into synovial fluid.

The pattern of preformed cytokines in tissues frequently affected by blunt trauma

The aim of this prospective study was to determine the local concentrations of inflammatory mediators in various tissue types frequently affected by trauma to estimate the role of prestored cytokine release by mechanical tissue trauma in the induction of a systemic inflammatory response syndrome. The degree of tissue damage, evaluated by its systemic release of inflammatory mediators, represents an important factor concerning the outcome of trauma patients. Clinical trials indicate that the kind of traumatized tissue influences the cytokine pattern measured in patients blood afterwards. However, the tissue-specific mediator composition underlying this systemic mediator release is rarely elucidated. Upon approval of the local IRB/EC, skin, subcutaneous fat, muscle, cancellous bone, and lung tissue were obtained during standard surgical procedures. The protein-based concentrations of Interleukin (IL)-6, IL-8, IL-10, and IL-12 were determined in tissue homogenates by enzyme-linked immunoabsorbant assay (ELISA; n = 60 samples). Albumin was measured to evaluate the degree of blood contamination of tissue samples. IL-6 and IL-8 were consistently detectable in more than 95% of the tissue specimens. Lung and cancellous bone presented by far the highest concentrations of these cytokines, whereas skin, subcutaneous fat, and muscle showed significantly lower levels. IL-10 was not detectable in 88%; IL-12 could not be measured in 63% of the samples. Cytokine concentrations did not correlate with the amount of albumin measured in tissue specimens. Due to their consistent presence at the tissue level, high systemic concentrations of IL-6 and IL-8 in patients blood, seen after pulmonary trauma, long bone fractures, or soft tissue injury, may be interpreted as an overspill of local trauma mediators. This indicates their relevance in post-traumatic monitoring. Furthermore, albumin is a suitable and necessary indicator to evaluate influences of possible blood contamination in tissue samples.

JAK/STAT but not ERK1/ERK2 pathway mediates interleukin (IL)-6/soluble IL-6R down-regulation of Type II collagen, aggrecan core, and link protein transcription in articular chondrocytes. Association with a down-regulation of SOX9 expression

Signal transducers and activators of transcription (STAT) factors are cytoplasmic proteins that can be activated by Janus kinases (JAK) and that modulate gene expression in response to cytokine receptor stimulation. STAT proteins dimerize, translocate into the nucleus, and activate specific target genes. In the present study, we show for the first time that interleukin-6 (IL), in the presence of its soluble receptor (sIL-6R), induces activation of JAK1, JAK2, and STAT1/STAT3 proteins in bovine articular chondrocytes. Western blotting and mobility shift assays demonstrated that this effect is accompanied by the DNA binding of the STAT proteins. The mitogen-activated protein kinase pathway was also activated in response to IL-6/sIL-6R association, as reflected by phosphorylation of ERK1 and ERK2 proteins. In these conditions, the expression of cartilage-specific matrix genes, type II collagen, aggrecan core, and link proteins was found to be markedly down-regulated. This negative effect was abolished by addition of parthenolide, an inhibitor of the STAT activation, whereas blockade of the MAP kinases with PD098059 was without significant effect. Thus, activation of the STAT signaling pathways, but not ERK-dependent pathways, is essential for down-regulation of the major cartilage-specific matrix genes by IL-6. In addition, a parallel reduction of Sox9 expression, a key factor of chondrocyte phenotype, was found in these experimental conditions. These IL-6 effects might contribute to the phenotype loss of chondrocytes in joint diseases and the alteration of articular cartilage associated with this pathology.

Bone turnover markers and cytokines in joint fluid: analyses in 10 patients with loose hip prosthesis and 39 with coxarthrosis

We analyzed bone turnover markers (osteocalcin, bone ALP, beta-crosslaps-CTX) and cytokines (IL-1, IL-8 and IL-10) in hip joint fluid in 10 patients before revision surgery and in 39 with idiopathic coxarthrosis. Patients with loose implants had lower concentrations of resorption marker than those with arthrosis (0.8 vs 1.3 ng/mL), but bone formation marker osteocalcin was reduced (4.2 vs 22.6 ng/mL). IL-8 and IL-10 levels were elevated in patients with implant failure (870 vs 340 pg/mL; 14.3 vs 4.0 pg/mL). We found a negative correlation between the bone resorption marker (CTX) and IL-10 in cases with prosthesis loosening and a positive correlation between IL-10 and time-to-revision. We conclude that enhanced local production of inflammatory cytokines leading to suppressed bone formation is a part of the loosening process. The expression of anti-inflammatory mediators is not sufficient to counteract the imbalance in bone turnover.