Non-Transcriptional and Translational Function of Canonical NF-κB Signaling in Activating ERK1/2 in IL-1ß-Induced COX-2 Expression in Synovial Fibroblasts.

The pro-inflammatory cytokine interleukin 1ß (IL-1ß) induces the synthesis of prostaglandin E2 by upregulating cyclooxygenase-2 (COX-2) in the synovial tissue of individuals with autoimmune diseases, such as rheumatoid arthritis (RA). IL-1ß-mediated stimulation of NF-κB and MAPK signaling is important for the pathogenesis of RA; however, crosstalk(s) between NF-κB and MAPK signaling remains to be understood. In this study, we established a model for IL-1ß-induced synovitis and investigated the role of NF-κB and MAPK signaling in synovitis. We observed an increase in the mRNA and protein levels of COX-2 and prostaglandin E2 release in cells treated with IL-1ß. NF-κB and ERK1/2 inhibitors significantly reduced IL-1ß-induced COX-2 expression. IL-1ß induced the phosphorylation of canonical NF-κB complex (p65 and p105) and degradation of IκBα. IL-1ß also induced ERK1/2 phosphorylation but did not affect the phosphorylation levels of p38 MAPK and JNK. IL-1ß failed to induce COX-2 expression in cells transfected with siRNA for p65, p105, ERK1, or ERK2. Notably, NF-κB inhibitors reduced IL-1ß-induced ERK1/2 phosphorylation; however, the ERK1/2 inhibitor had no effect on the phosphorylation of the canonical NF-κB complex. Although transcription and translation inhibitors had no effect on IL-1ß-induced ERK1/2 phosphorylation, the silencing of canonical NF-κB complex in siRNA-transfected fibroblasts prevented IL-1ß-induced phosphorylation of ERK1/2. Taken together, our data indicate the importance of the non-transcriptional/translational activity of canonical NF-κB in the activation of ERK1/2 signaling involved in the IL-1ß-induced development of autoimmune diseases affecting the synovial tissue, such as RA.

Curcumin alleviates rheumatoid arthritis-induced inflammation and synovial hyperplasia by targeting mTOR pathway in rats.

PURPOSE: Rheumatoid arthritis (RA) is a chronic, progressive autoimmune disease characterized by aggressive and symmetric polyarthritis. Mammalian target of rapamycin (mTOR) was reported to be a new target for RA therapy and its inhibitor rapamycin can significantly reduce the invasive force of fibroblast-like synoviocytes. Here, we determined the effect of curcumin to alleviate inflammation and synovial hyperplasia for the therapy of RA. MATERIALS AND METHODS: Collagen-induced arthritis (CIA) was developed in Wistar rats and used as a model resembling RA in humans. Rats were treated with curcumin (200 mg/kg) and the mTOR inhibitor rapamycin (2.5 mg/kg) daily for 3 weeks. Effects of the treatment on local joint, peripheral blood, and synovial hyperplasia in the pathogenesis of CIA were analyzed. RESULTS: Curcumin and rapamycin significantly inhibited the redness and swelling of ankles and joints in RA rats. Curcumin inhibited the CIA-induced mTOR pathway and the RA-induced infiltration of inflammatory cells into the synovium. Curcumin and rapamycin treatment inhibited the increased levels of proinflammatory cytokines including IL-1ß, TNF-α, MMP-1, and MMP-3 in CIA rats. CONCLUSION: Our findings show that curcumin alleviates CIA-induced inflammation, synovial hyperplasia, and the other main features involved in the pathogenesis of CIA via the mTOR pathway. These results provide evidence for the anti-arthritic properties of curcumin and corroborate its potential use for the treatment of RA.

Hexokinase 2 as a novel selective metabolic target for rheumatoid arthritis.

OBJECTIVES: Recent studies indicate that glucose metabolism is altered in rheumatoid arthritis (RA) fibroblast-like synoviocytes (FLS). Hexokinases (HKs) catalyse the first step in glucose metabolism, and HK2 constitutes the principal HK inducible isoform. We hypothesise that HK2 contributes to the synovial lining hypertrophy and plays a critical role in bone and cartilage damage. METHODS: HK1 and HK2 expression were determined in RA and osteoarthritis (OA) synovial tissue by immunohistochemistry. RA FLS were transfected with either HK1 or HK2 siRNA, or infected with either adenovirus (ad)-GFP, ad-HK1 or ad-HK2. FLS migration and invasion were assessed. To study the role of HK2 in vivo, 108 particles of ad-HK2 or ad-GFP were injected into the knee of wild-type mice. K/BxN serum transfer arthritis was induced in HK2F/F mice harbouring Col1a1-Cre (HK2Col1), to delete HK2 in non-haematopoietic cells. RESULTS: HK2 is particular of RA histopathology (9/9 RA; 1/8 OA) and colocalises with FLS markers. Silencing HK2 in RA FLS resulted in a less invasive and migratory phenotype. Consistently, overexpression of HK2 resulted in an increased ability to migrate and invade. It also increased extracellular lactate production. Intra-articular injection of ad-HK2 in normal knees dramatically increased synovial lining thickness, FLS activation and proliferation. HK2 was highly expressed in the synovial lining after K/BxN serum transfer arthritis. HK2Col1 mice significantly showed decreased arthritis severity, bone and cartilage damage. CONCLUSION: HK2 is specifically expressed in RA synovial lining and regulates FLS aggressive functions. HK2 might be an attractive selective metabolic target safer than global glycolysis for RA treatment.

The role of molecular pain biomarkers in temporomandibular joint internal derangement.

There is evidence that low-grade inflammation may be responsible for pain and development of degenerative changes in temporomandibular joint internal derangement. This article reviews the current knowledge of the molecular mechanisms behind TMJ internal derangements. A non-systematic search was carried out in PubMed, Embase and the Cochrane library for studies regarding pathophysiological mechanisms behind internal derangements focusing on pain-mediating inflammatory and cartilage-degrading molecules. Recent data suggest that release of cytokines may be the key event for pain and cartilage destruction in TMJ internal derangements. Cytokines promote the release of matrix metalloproteinases (MMPs), and due to hypoxia, vascular endothelial growth factor (VEGF) is released. This activates chondrocytes to produce MMPs and reduce their tissue inhibitors (TIMPs) as well as the recruitment of osteoclasts, ultimately leading to cartilage and bone resorption. Also, proteoglycans have an important role in this process. Several cytokines, MMPs, TIMPs and VEGF have been identified in higher concentrations in the TMJ synovial fluid of patients with painful internal derangements and shown to be associated with the degree of degeneration. Other molecules that show elevated levels include hyaluronic acid synthase, disintegrin and metalloproteinase with thrombospondin motifs (ADAMTs), aggrecan, fibromodulin, biglycan and lumican. Taken together, more or less pronounced inflammation of TMJ structures with release of cytokines, MMPs and other molecular markers that interact in a complex manner may be responsible for tissue degeneration in internal derangements. As internal derangements may be symptom-free, the degree of inflammation, but also other mechanisms, may be important for pain development.

Differential glucocorticoid metabolism in patients with persistent versus resolving inflammatory arthritis.

INTRODUCTION: Impairment in the ability of the inflamed synovium to generate cortisol has been proposed to be a factor in the persistence and severity of inflammatory arthritis. In the inflamed synovium, cortisol is generated from cortisone by the 11ß-hydroxysteroid dehydrogenase type 1 (11ß-HSD1) enzyme. The objective of this study was to determine the role of endogenous glucocorticoid metabolism in the development of persistent inflammatory arthritis. METHODS: Urine samples were collected from patients with early arthritis (symptoms ≤12 weeks duration) whose final diagnostic outcomes were established after clinical follow-up and from patients with established rheumatoid arthritis (RA). All patients were free of disease-modifying anti-rheumatic drugs at the time of sample collection. Systemic measures of glucocorticoid metabolism were assessed in the urine samples by gas chromatography/mass spectrometry. Clinical data including CRP and ESR were also collected at baseline. RESULTS: Systemic measures of 11ß-HSD1 activity were significantly higher in patients with early arthritis whose disease went on to persist, and also in the subgroup of patients with persistent disease who developed RA, when compared with patients whose synovitis resolved over time. We observed a significant positive correlation between systemic 11ß-HSD1 activity and ESR/CRP in patients with established RA but not in any of the early arthritis patients group. CONCLUSIONS: The present study demonstrates that patients with a new onset of synovitis whose disease subsequently resolved had significantly lower levels of systemic 11ß-HSD1 activity when compared with patients whose synovitis developed into RA or other forms of persistent arthritis. Low absolute levels of 11ß-HSD1 activity do not therefore appear to be a major contributor to the development of RA and it is possible that a high total body 11ß-HSD1 activity during early arthritis may reduce the probability of disease resolution.

Synovitis biomarkers: ex vivo characterization of three biomarkers for identification of inflammatory osteoarthritis.

OBJECTIVE: Characterize biomarkers measuring extracellular matrix turnover of inflamed osteoarthritis synovium. METHODS: Human primary fibroblast-like synoviocytes and synovial membrane explants (SMEs) treated with various cytokines and growth factors were assessed by C1M, C3M, and acMMP3 in the conditioned medium. RESULTS: TNFα significantly increased C1M up to seven-fold (p = 0.0002), C3M up to 24-fold (p = 0.0011), and acMMP3 up to 14-fold (p < 0.0001) in SMEs. IL-1ß also significantly increased C1M up to five-fold (p = 0.00094), C3M four-fold (p = 0.007), and acMMP3 18-fold (p < 0.0001) in SMEs. CONCLUSION: The biomarkers C1M, C3M, and acMMP-3 were synovitis biomarkers ex vivo and provide a translational tool together with the SME model.

Serum matrix metalloproteinase-3 as a noninvasive biomarker of histological synovitis for diagnosis of rheumatoid arthritis.

OBJECTIVE: To explore the correlation between matrix metalloproteinase- (MMP-) 3 and histological synovitis in rheumatoid arthritis (RA). METHODS: Serum MMP-3 of 62 patients with active RA was detected by ELISA. Serial synovial tissue sections from all RA patients, 13 osteoarthritis, and 10 orthopedic arthropathies patients were stained with hematoxylin and eosin and immunohistochemically for MMP-3, CD3, CD20, CD38, CD68, and CD15. RESULTS: The percentage of lining MMP3+ cells was significantly higher in RA patients especially with high grade synovitis and it was significantly correlated with Krenn's synovitis score (r = 0.574, P < 0.001) and sublining inflammatory cells. Multivariate stepwise linear regression analysis revealed that the association of the percentage of lining MMP3+ cells with activation of synovial stroma, sublining CD68+ macrophages, and CD15+ neutrophils was stronger than other histological indicators. The percentage of lining MMP3+ cells was significantly correlated with serum MMP-3 in RA (r = 0.656, P < 0.001). Serum MMP-3 was higher in RA patients with high grade synovitis than that of low grade synovitis and significantly correlated with synovitis score and activation of synovial stroma subscore (all P < 0.05). CONCLUSION: Serum MMP-3 may be an alternative noninvasive biomarker of histological synovitis and RA diagnosis.

Blau syndrome polymorphisms in NOD2 identify nucleotide hydrolysis and helical domain 1 as signalling regulators.

Understanding how single nucleotide polymorphisms (SNPs) lead to disease at a molecular level provides a starting point for improved therapeutic intervention. SNPs in the innate immune receptor nucleotide oligomerisation domain 2 (NOD2) can cause the inflammatory disorders Blau Syndrome (BS) and early onset sarcoidosis (EOS) through receptor hyperactivation. Here, we show that these polymorphisms cluster into two primary locations: the ATP/Mg(2+)-binding site and helical domain 1. Polymorphisms in these two locations may consequently dysregulate ATP hydrolysis and NOD2 autoinhibition, respectively. Complementary mutations in NOD1 did not mirror the NOD2 phenotype, which indicates that NOD1 and NOD2 are activated and regulated by distinct methods.

Brief report: carboxypeptidase B serves as a protective mediator in osteoarthritis.

OBJECTIVE: We previously demonstrated that carboxypeptidase B (CPB) protects against joint erosion in rheumatoid arthritis by inactivating complement component C5a. We also found that levels of CPB are abnormally high in the synovial fluid of individuals with another joint disease, osteoarthritis (OA). We undertook this study to investigate whether CPB plays a role in the pathogenesis of OA. METHODS: We compared the development of OA in CPB-deficient (Cpb2(-/-) ) mice and wild-type mice by subjecting them to medial meniscectomy and histologically assessing cartilage damage, osteophyte formation, and synovitis in the stifle joints 4 months later. We measured levels of proCPB, proinflammatory cytokines, and complement components in synovial fluid samples from patients with symptomatic and radiographic knee OA. Finally, we used enzyme-linked immunosorbent assay, flow cytometry, and hemolytic assays to assess the effect of CPB on formation of membrane attack complex (MAC)-a complement effector critical to OA pathogenesis. RESULTS: Cpb2(-/-) mice developed dramatically greater cartilage damage than did wild-type mice (P < 0.01) and had a greater number of osteophytes (P < 0.05) and a greater degree of synovitis (P < 0.05). In synovial fluid samples from OA patients, high levels of proCPB were associated with high levels of proinflammatory cytokines and complement components, and levels of proCPB correlated positively with those of MAC. In in vitro complement activation assays, activated CPB suppressed the formation of MAC as well as MAC-induced hemolysis. CONCLUSION: Our data suggest that CPB protects against inflammatory destruction of the joints in OA, at least in part by inhibiting complement activation.

Equine myeloperoxidase: a novel biomarker in synovial fluid for the diagnosis of infection.

REASONS FOR PERFORMING STUDY: Equine joint infection is a life-threatening disorder, and confirmation of the diagnosis can be difficult. Synovial fluid biomarkers may assist the discrimination between infectious and noninfectious joint disease. OBJECTIVES: This study investigates whether the immunological detection of total and enzymatically active myeloperoxidase (MPO) assists the diagnosis of joint infection in horses. METHODS: The following 4 sample groups were included: healthy; osteochondritis dissecans (OCD); traumatic synovitis; and culture-confirmed infected joints. Synovial fluid was analysed for total MPO by a horse-specific sandwich enzyme-linked immunosorbent assay (ELISA) and for active MPO using the specific immunological extraction followed by enzymatic detection (SIEFED) technique. Western blot analysis was performed to confirm the antibody specificity. RESULTS: Synovial fluid from infected joints contained significantly more total and active MPO than samples from healthy joints, joints affected by OCD and joints with traumatic synovitis. Cut-off values were set at 5000 and 350 ng/ml for total and active MPO, respectively, with fair sensitivity, specificity, positive and negative predictive values and likelihood ratios for infection. Correlation coefficients were reported between the total as well as the active MPO levels and the routine synovial fluid parameters, i.e. the white blood cell count, the neutrophil count and the total protein level. No correlation was observed between MPO and either the age of the horse or the joint affected. Western blotting confirmed the antibody specificity for equine MPO. CONCLUSIONS AND POTENTIAL RELEVANCE: Synovial fluid MPO was identified as a very promising biomarker to augment the discrimination of infectious vs. noninfectious joint disease in horses. Both ELISA and SIEFED techniques can be used for its specific and rapid detection. The analysis of synovial fluid MPO can be used as a complementary test to aid in the discrimination between infectious and noninfectious joint disease, especially when the white blood cell counts and the total protein level are inconclusive.

Ultrasonographic measures of synovitis in an early phase clinical trial: a double-blind, randomised, placebo and comparator controlled phase IIa trial of GW274150 (a selective inducible nitric oxide synthase inhibitor) in rheumatoid arthritis.

OBJECTIVES: To test the sensitivity to change of ultrasonographic endpoints in early phase clinical trials in subjects with active rheumatoid arthritis (RA). METHODS: A double-blind, placebo and comparator controlled, randomised, two-centre study investigated the effect on synovial thickness and vascularity of 28 days repeat daily oral dosing of 60 mg of the inducible nitric oxide synthase inhibitor GW274150 or 7.5 mg prednisolone in RA. Fifty patients with DAS28 scores ≥4.0 were assigned to 3 treatment arms of 17, 19 and 14 (on placebo, GW274150 and prednisolone respectively). Synovial thickness and vascularity of all 10 metacarpophalangeal joints were assessed by ultrasonography using a semi-quantitative scale at baseline (Day 1), Day 15 and Day 28. Vascularity was also measured quantitatively by power Doppler area. RESULTS: At Day 28, the GW274150 group showed a trend towards reduction in synovial thickness compared with placebo, with an adjusted mean decrease of 33% (p=0.072); the prednisolone group decreased significantly by 44% (p=0.011). Similarly, there was a trend to reduced synovial vascularity with GW274150 by 42% compared with placebo (p=0.075); prednisolone resulted in a statistically significant decrease of 55% (p=0.012). There was a 55% decrease in power Doppler area for GW274150, compared with placebo although the result was not statistically significant (p=0.375). Prednisolone 7.5 mg resulted in a highly statistically significant decrease of 95% (p=0.003). CONCLUSIONS: This study advocates the use of ultrasonographic measures of metacarpophalangeal joint synovitis as an endpoint for clinical studies assessing therapeutic potential of new compounds in small patient cohorts over 28 days.

T cell protein tyrosine phosphatase deficiency results in spontaneous synovitis and subchondral bone resorption in mice.

OBJECTIVE: T cell protein tyrosine phosphatase (TC-PTP) is an important regulator of hematopoiesis and cytokine signaling. Recently, several genome-wide association studies have identified single-nucleotide polymorphisms (SNPs) in the locus of TC-PTP that are associated with rheumatoid arthritis and juvenile idiopathic arthritis, among other autoimmune diseases. The aim of this study was to evaluate the effect of TC-PTP deficiency on the bone and joint environment using a knockout mouse model. METHODS: Radiographic and micro-computed tomography analyses were performed on femurs of 3-week-old mice. In addition, the femorotibial joints were assessed by histology, flow cytometry, and cytokine detection. RESULTS: Deficiency of TC-PTP resulted in decreased bone volume as well as an increase in osteoclast density within the mouse femurs. In addition, synovitis, characterized by infiltration of mixed inflammatory cell types and proinflammatory cytokines, developed in the knee joints of TC-PTP(-/-) mice. CONCLUSION: These findings demonstrate that loss of TC-PTP expression results in synovitis with several hallmarks of inflammatory arthritis. The inflammatory environment observed in the knee joints of TC-PTP(-/-) mice differs from the systemic inflammation previously described in these mice and merits further research into the role of TC-PTP in the synovium. Furthermore, the results support recently described associations between SNPs in the TC-PTP locus and arthritis incidence.

Low-intensity pulsed ultrasound reduces the inflammatory activity of synovitis.

The purpose of this study was to examine the effect of low-intensity pulsed ultrasound (LIPUS) on the cell proliferation and growth of synovial membrane cells stimulated with inflammatory cytokines, and to evaluate the effectiveness of LIPUS treatment of synovitis in the knee joints of animal models for rheumatoid arthritis. The rabbit knee synovial membrane cell line, HIG-82, was cultured in medium with or without IL-1ß or TNF-α. Four hours after stimulation with the cytokines, the cells received LIPUS or sham exposure. Cell proliferation and growth were then analyzed. Using MRL/lpr mice, the anti-inflammatory effects of LIPUS were also evaluated in vivo. Stimulation with proinflammatory cytokines significantly up-regulated cell proliferation which was significantly down-regulated by LIPUS exposure. In MRL/lpr mice, exposure of knee joints to LIPUS caused a significant reduction of histological damage compared to the control. Histological lesions were significantly reduced in the joints treated with LIPUS for 3 weeks. Cox-2-positive cells in the knee joints treated with LIPUS were markedly decreased compared to the control joints. Therefore, LIPUS stimulation may be a medical treatment for joint inflammatory diseases, such as synovitis.

Inhibition of fms-like tyrosine kinase 3 alleviates experimental arthritis by reducing formation of dendritic cells and antigen presentation.

TKs are intracellular signaling molecules essential for cell homeostasis. Inhibition of TKs is used in treatment of malignancies and diabetes mellitus. The present study evaluated the role of Flt3 in antigen-induced arthritis. Mice were immunized with mBSA, and arthritis was induced by an i.a. injection of mBSA. Treatment with the Flt3 inhibitor sunitinib was started together with mBSA immunization or together with the induction of arthritis. The mBSA-injected joints were evaluated morphologically for signs of synovitis and bone/cartilage destruction. Markers of bone metabolism and antibody responses were measured by ELISA. Maturation of DCs in the bone marrow and spleen was evaluated by flow cytometry. Sunitinib treatment reduced the intensity of synovitis and the incidence of bone destruction. The reduction in bone destruction was seen when the treatment was started at the time of immunization or at the time of arthritis induction. The antiarthritic effect was achieved by inhibition of DCs, reduction of antibody production, and bone metabolism. Inhibition of Flt3 is a potent antiarthritic mechanism reducing antigen presentation, synovial inflammation, and bone resorption. Down-regulation of TKs may be a useful tool in the treatment of human RA.

Platelets participate in synovitis via Cox-1-dependent synthesis of prostacyclin independently of microparticle generation.

In addition to the well-described role of platelets in thrombosis, a growing body of evidence implicates platelets in diverse inflammatory responses. We recently showed platelets can contribute to the pathophysiology of inflammatory arthritis via IL-1- containing microparticles. In this study, we demonstrate that platelets, and not platelet microparticles, actively contribute to synovitis via production of proinflammatory prostacyclin in an autoimmune arthritis model. Using both genetic and pharmacologic approaches, we establish that paracrine production of prostacyclin proceeds in the absence of cyclooxygenase-2. Furthermore, we also demonstrate that prostacyclin generation can arise via transcellular collaboration between platelets and fibroblast-like synoviocytes. In addition to shedding light on an unappreciated pathway of lipid synthesis in arthritis, we further delineate a novel effector activity by which platelets can contribute to inflammatory disease.

Phosphodiesterase 4 (PDE4) regulation of proinflammatory cytokine and chemokine release from rheumatoid synovial membrane.

BACKGROUND: The cAMP-metabolising enzyme, phosphodiesterase 4 (PDE4), has been implicated in a number of immune responses, including tumour necrosis factor α (TNFα) production. To date, few data have directly addressed whether synovial cytokine and chemokine production is modified by PDE4. OBJECTIVE: Using specific PDE4 inhibitors, roflumilast plus two novel inhibitors, INH 0061 and INH 0062, the authors studied the effect of PDE4 inhibition on proinflammatory cytokine and chemokine release from primary rheumatoid arthritis (RA) synovial digest suspensions and in a macrophage T cell co-culture assay system. RESULTS: All PDE4 inhibitors dose-dependently reduced the release of TNFα from primary synovial membrane cultures (n=5), half maximal inhibitory concentration (IC(50)) 300-30 nM, p<0.05. Similarly, a significant suppression in the release the proinflammatory chemokines, monocyte chemoattractant protein-1 (MCP-1), macrophage inflammatory protein (MIP)-1α, MIP-1ß (IC(50) 300-30 nM) and regulated upon activation normal T-cell expressed and secreted (RANTES) (IC(50) 3 nM) was also observed, p<0.05. While interleukin 1ß was also reduced, it did not achieve an IC(50). These observations were further confirmed in a macrophage T cell co-culture system, demonstrating the importance of PDE4 pathways in regulating cytokine/chemokine release in a cellular interaction implicated in inflammatory synovitis. Subsequent studies using the human monocytic cell line U937 also demonstrated cytokine regulation with PDE4 knockdown utilising a small interfering RNA approach. CONCLUSION: These data provide direct evidence of PDE4-dependent pathways in human RA synovial inflammatory cytokine and chemokine release and may provide a novel approach in treating chronic autoimmune conditions such as RA.

Expression of ß-1,4-galactosyltransferase I in a surgically-induced rat model of knee osteoarthritic synovitis.

BACKGROUND: There are few reports of a biological role for glycosyltransferases in the infiltration of osteoarthritic synovitis. The aim of this research was to investigate the expression and cellular location of ß-1,4-galactosyltransferase I (ß-1,4-GalT-I) in a surgically-induced rat model of knee osteoarthritis (OA), and explore the role of ß-1,4-GalT-I in the pathogenesis of OA. METHODS: Male Sprague-Dawley rats were randomly divided into three groups: OA group, sham group and normal group. The model of OA was established in the right knees of rats by anterior cruciate ligament transaction (ACLT) with partial medial meniscectomy. Fibroblast-like synoviocytes (FLSs) obtained from normal rat synovial tissue were cultured. The expression of ß-1,4-GalT-I mRNA in the synovial tissue, articular cartilage and FLSs treated with tumor necrosis factor-α (TNF-α) were assayed by real-time PCR. Western-blotting and immunohistochemisty were used to observe the expression of ß-1,4-GalT-I at the protein level. Double immunofluorescent staining was used to define the location of the ß-1,4-GalT-I with macrophage-like synoviocytes, FLSs, neutrophils, and TNF-α in the OA synovium. The alteration of TNF-α in FLSs which were treated with lipopolysaccharide (LPS) and ß-1,4-GalT-I-Ab were detected by enzyme-linked immunosorbent assay (ELISA). RESULTS: The mRNA and protein expression of ß-1,4-GalT-I increased in synovial tissue of the OA group compared with the normal and sham groups at two and four weeks after the surgery, however, no significant difference appeared in the articular cartilage. Immunohistochemistry also indicated that the ß-1,4-GalT-I expression in OA synovium at four weeks after surgery increased sharply compared with the control group. ß-1,4-GalT-I co-localized with macrophage-like synoviocytes, FLSs, neutrophils and TNF-α in rat OA synovitis. Moreover, in vitro ß-1,4-GalT-I mRNA in FLSs was affected in a dose- and time-dependent manner in response to TNF-α stimulation. ELISA revealed that the expression of TNF-α was attenuated in FLSs in vitro when treated with anti ß-1,4-GalT-I antibody. CONCLUSION: ß-1,4-GalT-I may play an important role in the inflammation process of rat OA synovial tissue which would provide the foundation for further researching into the concrete mechanism of ß-1,4-GalT-I in OA synovitis.

Genetic sphingosine kinase 1 deficiency significantly decreases synovial inflammation and joint erosions in murine TNF-alpha-induced arthritis.

Sphingosine kinase 1 (SphK1) is an enzyme that converts sphingosine to bioactive sphingosine-1-phosphate. Recent in vitro data suggest a potential role of SphK1 in TNF-alpha-mediated inflammation. Our aims in this study were to determine the in vivo significance of SphK1 in TNF-alpha-mediated chronic inflammation and to define which pathogenic mechanisms induced by TNF-alpha are SphK1 dependent. To pursue these aims, we studied the effect of SphK1 deficiency in an in vivo model of TNF-alpha-induced chronic inflammatory arthritis. Transgenic hTNF-alpha mice, which develop spontaneous inflammatory erosive arthritis beginning at 14-16 wk, were crossed with SphK1 null mice (SphK1(-/-)), on the C57BL6 genetic background. Beginning at 4 mo of age, hTNF/SphK1(-/-) mice had significantly less severe clinically evident paw swelling and deformity, less synovial and periarticular inflammation, and markedly decreased bone erosions as measured quantitatively through micro-CT images. Mechanistically, the mice lacking SphK1 had less articular cyclooxygenase 2 protein and fewer synovial Th17 cells than did hTNF/SphK1(+/+) littermates. Microarray analysis and real-time RT-PCR of the ankle synovial tissue demonstrated that hTNF/SphK1(-/-) mice had increased transcript levels of suppressor of cytokine signaling 3 compared with hTNF/SphK1(+/+) mice, likely also contributing to the decreased inflammation in the SphK1-deficient mice. Finally, significantly fewer mature osteoclasts were detected in the ankle joints of hTNF/SphK1(-/-) mice compared with hTNF/SphK1(+/+) mice. These data indicate that SphK1 plays a key role in hTNF-alpha-induced inflammatory arthritis via impacting synovial inflammation and osteoclast number.

Lymphotoxin-alphabeta heterotrimers are cleaved by metalloproteinases and contribute to synovitis in rheumatoid arthritis.

Tumor necrosis factor-superfamily (TNF-SF) members, lymphotoxin (LT)-alpha and LTbeta, are proinflammatory cytokines associated with pathology in rheumatoid arthritis. LTalpha3 homotrimers are secreted, whereas LTalpha(1)beta(2) heterotrimers are expressed on the surface of activated lymphocytes. As many TNF-SF members are actively cleaved from cell membranes, we determined whether LTalphabeta heterotrimers are also cleaved, and are biologically active in rheumatoid arthritis (RA) patients. LTalphabeta heterotrimers were detected in culture supernatants from activated human T-helper (Th) 0, Th1, and Th17 cells, together with LTalpha3 and TNFalpha. The heterotimers were actively cleaved from the cell surface by ADAM17 metalloproteinase (MMP) and MMP-8, and cleavage was inhibited by TAPI-1, a TNF-alpha converting enzyme (TACE) inhibitor. Soluble LTalphabeta was detected in serum from both normal donors and RA patients, and was elevated in synovial fluid from RA patients compared to osteoarthritis (OA) patients. Levels of LTalphabeta in RA patient synovial fluid correlated with increased TNFalpha, IL-8, IL-12, IL-1beta, IFN-gamma, and IL-6 cytokines. Moreover, recombinant LTalpha1beta2-induced CXCL1, CXCL2, IL-6, IL-8, VCAM-1, and ICAM-1 from primary synovial fibroblasts isolated from RA patients. Therefore, soluble LTalphabeta in synovial fluid is associated with a proinflammatory cytokine milieu that contributes to synovitis in RA.

Differing effects of exogenous and endogenous hydrogen sulphide in carrageenan-induced knee joint synovitis in the rat.

BACKGROUND AND PURPOSE: Recent findings suggest that the noxious gas H(2)S is produced endogenously, and that physiological concentrations of H(2)S are able to modulate pain and inflammation in rodents. This study was undertaken to evaluate the ability of endogenous and exogenous H(2)S to modulate carrageenan-induced synovitis in the rat knee. EXPERIMENTAL APPROACH: Synovitis was induced in Wistar rats by intra-articular injection of carrageenan into the knee joint. Sixty minutes prior to carrageenan injection, the rats were pretreated with indomethacin, an inhibitor of H(2)S formation (DL-propargylglycine) or an H(2)S donor [Lawesson's reagent (LR)]. KEY RESULTS: Injection of carrageenan evoked knee inflammation, pain as characterized by impaired gait, secondary tactile allodynia of the ipsilateral hindpaw, joint swelling, histological changes, inflammatory cell infiltration, increased synovial myeloperoxidase, protein nitrotyrosine residues, inducible NOS (iNOS) activity and NO production. Pretreatment with LR or indomethacin significantly attenuated the pain responses, and all the inflammatory and biochemical changes, except for the increased iNOS activity, NO production and 3-NT. Propargylglycine pretreatment potentiated synovial iNOS activity (and NO production), and enhanced macrophage infiltration, but had no effect on other inflammatory parameters. CONCLUSIONS AND IMPLICATIONS: Whereas exogenous H(2)S delivered to the knee joint can produce a significant anti-inflammatory and anti-nociceptive effect, locally produced H(2)S exerts little immunomodulatory effect. These data further support the development and use of H(2)S donors as potential alternatives (or complementary therapies) to the available anti-inflammatory compounds used for treatment of joint inflammation or relief of its symptoms.