Proliferation Of Rheumatoid Arthritis Synovial Fibroblasts Research Articles

Effects of a novel tyrosine kinase inhibitor in rheumatoid arthritis synovial fibroblasts

Objective:Biologicals have revolutionised the treatment of rheumatoid arthritis (RA). However, progressive joint destruction can still be observed in many patients and the search for novel molecular therapies targeting specific signalling...

Ganoderma lucidum polysaccharide peptide reduced the production of proinflammatory cytokines in activated rheumatoid synovial fibroblast

The aim of the current study was to elucidate the potential therapeutic effect of Ganoderma lucidum polysaccharide peptide (GL-PP) in rheumatoid arthritis (RA). The effects of GL-PP on cell proliferation and cytokine production were studied in RA synovial fibroblasts (RASF). GL-PP significantly inhibited the proliferation of RASF. Following the incubation with GL-PP, production of interleukin (IL)-6 and monocyte chemoattractant protein (MCP)-1 in RASF were significantly increased as expressed as percentage change from basal values. However, the actual effects were minimal due to the low basal values. When RASF were activated by IL-1beta or lipopolysaccharides, IL-8 and MCP-1 production increased many folds. GL-PP significantly suppressed their productions. The inhibitory effects of GL-PP on cytokine production in RASF were at least in part, by inhibiting the nuclear factor-kappa B (NF-kappaB) transcription pathway. Our results demonstrated that GL-PP had the unique ability to modulate cytokine production in RASF and warrants further investigation into its mechanism of action.

Oncostatin M induces angiogenesis and cartilage degradation in rheumatoid arthritis synovial tissue and human cartilage cocultures

To investigate the role of oncostatin M (OSM) in cell adhesion, angiogenesis, and matrix degradation in rheumatoid arthritis (RA) synovial tissue and normal human cartilage. Human dermal microvascular endothelial cell (HDMEC) and RA synovial fibroblast (RASF) proliferation and intercellular adhesion molecule 1 (ICAM-1) and vascular cell adhesion molecule 1 (VCAM-1) expression were assessed by a bromodeoxyuridine proliferation assay and flow cytometry. HDMEC tubule formation and migration were assessed by Matrigel culture and migration assay. Production of matrix metalloproteinase (MMP) and tissue inhibitor of metalloproteinases 1 (TIMP-1) in RA synovial explants, and proteoglycan/glycosaminoglycan (GAG) release, vascular endothelial growth factor (VEGF), and angiopoietin 2 production from RASF/normal cartilage cocultures were assessed by enzyme-linked immunosorbent assay and immunohistology. HDMEC/RASF proliferation was induced by OSM and interleukin-1beta (IL-1beta), alone and in combination. OSM enhanced cell surface expression of ICAM-1, but not VCAM-1, on endothelial cells and RASFs. OSM increased endothelial cell tubule formation and migration. In RA synovial explants, OSM induced production of MMP-1 and TIMP-1. When OSM was combined with IL-1beta, however, the MMP-1:TIMP-1 ratio was significantly increased. OSM potentiated IL-1beta-induced MMP-1 and MMP-13 expression in normal human cartilage/RASF cocultures, resulting in a significant increase in the MMP:TIMP ratio. In OSM/IL-1beta- stimulated cocultures, cartilage sections demonstrated significant proteoglycan depletion that was paralleled by a significant increase in GAG release in supernatants. Finally, compared with either cytokine alone, the combination of OSM and IL-1beta significantly induced VEGF production in RASF/cartilage cocultures. These data suggest that OSM promotes angiogenesis and endothelial cell migration and potentiates the effects of IL-1beta in promoting extracellular matrix turnover and human cartilage degradation. Furthermore, the induction of VEGF in cocultures supports the hypothesis of a link between angiogenesis and cartilage degradation.

JAB1 Determines the Response of Rheumatoid Arthritis Synovial Fibroblasts to Tumor Necrosis Factor-α

Fibroblast-like synoviocytes (FLSs) of patients with rheumatoid arthritis (RA FLSs) exhibit prosurvival, rather than apoptotic, response to tumor necrosis factor (TNF)-alpha stimulation. Here, we show that JAB1 is a critical regulator of the TNF-alpha-mediated anti-apo-ptosis pathways in RA FLSs. We found that knockdown of JAB1 using small interfering (si)RNA led to restoration of the TNF-alpha-induced apoptosis response, reduction of nuclear factor-kappaB activity, delayed degradation of IkappaB-alpha, and inhibited phosphorylation of JNK. Analysis of the interactions of JAB1 by reciprocal co-immunoprecipitations and confocal microscopy revealed that JAB1 interacts with TNF receptor-associated-factor 2 (TRAF2). The generation of the anti-apoptotic signal on binding of TNF-alpha to the TNF receptor (TNFR)1 has been shown to be associated with the recruitment of TRAF2 to the TNFR1 in a process that requires ubiquitination of TRAF2 with lysine-63-linked polyubiquitin chains. We found that TNF-alpha stimulation of JAB1 siRNA-transfected RA FLSs failed to stimulate ubiquitination of TRAF2. Thus, we conclude that JAB1-regulated ubiquitination of TRAF2 is a novel mechanism whereby TNF-alpha can induce anti-apoptosis signaling and production of matrix metalloproteinases through activation of nuclear factor-kappaB and JNK in RA FLSs.

Transforming growth factor β stimulates rheumatoid synovial fibroblasts via the type II receptor

Transforming growth factor (TGF)-beta regulates the function of fibroblasts, and has been shown to have a role in the pathogenesis of rheumatoid arthritis (RA) because several studies have demonstrated the presence of TGF-beta in the synovial tissue and synovial fluids of RA patients. In this study, we examined the expression of TGF-beta receptors in synovial fibroblasts of patients with RA and demonstrated the significance in functional responses of synovial fibroblasts to TGF-beta in this disorder. Transforming growth factor beta1 stimulated the expression of connective tissue growth factor (CTGF) in fibroblasts of patients with RA more than in those of patients with osteoarthritis (OA). Transforming growth factor beta1 induced the chemotactic migration of RA synovial fibroblasts and inhibited their proliferation significantly more than OA synovial fibroblasts. Both RA and OA synovial fibroblasts expressed detectable amounts of TGF-beta receptor type II mRNA, but the expression was higher in RA patients than in OA patients, as assessed by reverse transcriptase-polymerase chain reaction. There was no significant difference in the expression of TGF-beta receptor type I or type III in synovial fibroblasts between RA and OA patients. These results indicate that synovial fibroblasts of RA patients express the increased TGF-beta receptor type II, which is associated with altered responses to TGF-beta observed in CTGF expression, chemotaxis, and proliferation of RA synovial fibroblasts, and may have an important role in the pathogenesis of RA.

Transforming growth factor β stimulates rheumatoid synovial fibroblasts via the type II receptor

Transforming growth factor (TGF)-β regulates the function of fibroblasts, and has been shown to have a role in the pathogenesis of rheumatoid arthritis (RA) because several studies have demonstrated the presence of TGF-β in the synovial tissue and synovial fluids of RA patients. In this study, we examined the expression of TGF-β receptors in synovial fibroblasts of patients with RA and demonstrated the significance in functional responses of synovial fibroblasts to TGF-β in this disorder. Transforming growth factor β1 stimulated the expression of connective tissue growth factor (CTGF) in fibroblasts of patients with RA more than in those of patients with osteoarthritis (OA). Transforming growth factor β1 induced the chemotactic migration of RA synovial fibroblasts and inhibited their proliferation significantly more than OA synovial fibroblasts. Both RA and OA synovial fibroblasts expressed detectable amounts of TGF-β receptor type II mRNA, but the expression was higher in RA patients than in OA patients, as assessed by reverse transcriptase–polymerase chain reaction. There was no significant difference in the expression of TGF-β receptor type I or type III in synovial fibroblasts between RA and OA patients. These results indicate that synovial fibroblasts of RA patients express the increased TGF-β receptor type II, which is associated with altered responses to TGF-β observed in CTGF expression, chemotaxis, and proliferation of RA synovial fibroblasts, and may have an important role in the pathogenesis of RA.

Small GTP-binding protein Rho-mediated signaling promotes proliferation of rheumatoid synovial fibroblasts

Rho is a major small GTP-binding protein that is involved in the regulation of various cell functions, including proliferation and cell migration, through activation of multiple signaling molecules in various types of cells. We studied its roles in synovial fibroblasts (SFs) in patients with rheumatoid arthritis (RA) and clarified its relevance to RA synovitis, with the following results. 1)We found that the thrombin receptor was overexpressed on RA synovial fibroblasts (RA SFs) and that thrombin induced a marked proliferation and progression of the cell cycle to the S phase in these cells. 2)We also found that thrombin efficiently activated Rho. 3)Rho activation and proliferation and the progression of the cell cycle to the S phase were completely blocked by p115RGS (an N-terminal regulator of the G-protein signaling domain of p115RhoGEF) and by the C-terminal fragments of Gα13 (an inhibitor of the interaction of receptors with G13). 4)Thrombin induced the secretion of IL-6 by RA SFs, but this action was blocked by p115RGS or Gα13. Our findings show that the actions of thrombin on the proliferation of RA SFs, cell-cycle progression to the S phase, and IL-6 secretion were mainly mediated by the G13 and RhoGEF pathways. These results suggest that p115RGS and Gα13 could be potent inhibitors of such functions. A rational design of future therapeutic strategies for RA synovitis could perhaps include the exploitation of the Rho pathway to directly reduce the growth of synovial cells.

Signaling pathways involved in TRAIL-induced rheumatoid arthritis synovial fibroblast proliferation

Tumor necrosis factor alpha-related apoptosis inducing ligand (TRAIL) is a pro-apoptotic factor that can also induce cell proliferation. The role of TRAIL in rheumatoid arthritis (RA) is still unclear. Previously, we reported that TRAIL induces RA fibroblast-like synoviocyte (FLS) proliferation. We now investigate the intracellular mechanisms involved in TRAIL-induced cell proliferation. Therefore, we tested the effect of TRAIL on signaling pathways including MAP kinases (p38 and ERK1/2) and PI3 kinase/Akt, known to control cell proliferation. For all these experiments, the concentration of TRAIL used to stimulate cell was 0.5 nM. TRAIL induced p38 MAP kinase but with a lower intensity in comparison with tumor necrosis factor alpha (TNF-α) (n = 3). TRAIL also induced ERK1/2 and Akt phosphorylation in RA FLS in a time-dependent manner, showing maximum activation between 5 and 10 min by western blot (n = 3). This kinetic and intensity of ERK and Akt activation were similar to positive control TNF-α (n = 3). The transcription factor NF-κB plays a major role in cell survival and is activated by MAP kinases and Akt. When NF-κB is activated, it translocates from the cytoplasm to the nucleus. We examined NF-κB translocation into the nucleus of RA FLS following TRAIL stimulation using immunofluorescence. RA FLS treated with TRAIL did not induce a nuclear uptake of NF-κB (n = 3). The percentages of RA FLS-positive NF-κB translocation was increased from 4.3 ± 0.9% to 8.9 ± 2.3% when stimulated with TRAIL. For the positive control IL-1β, this percentage increased to 97.9 ± 1.1%. This result was confirmed by western blot. To determine the implication of MAP kinases, and PI3 kinase/Akt in TRAIL-induced proliferation, we therefore tested different specific signaling inhibitors including PI3 kinase inhibitor LY294002, ERK1/2 inhibitor PD98059, and p38 inhibitor SB203580. RA FLS were pretreated with the specific inhibitors at different concentrations or Me2SO vehicle control for 1 hour and were then stimulated with TRAIL. Proliferation was assessed according to the level of incorporated tritiated thymidine. ERK 1/2 inhibitor PD98059 and p38 inhibitor SB203580 significantly downregulated TRAIL-induced proliferation in a dose-dependent manner (n = 3). PI3 kinase inhibitor LY294002 almost completely blocked proliferation promoted by TRAIL. These results highlight the main role of Akt in TRAIL-mediated proliferation.

Histone deacetylase inhibitor suppression of autoantibody-mediated arthritis in mice via regulation of p16INK4a and p21(WAF1/Cip1) expression.

To examine whether depsipeptide (FK228), a histone deacetylase (HDA) inhibitor, has inhibitory effects on the proliferation of synovial fibroblasts from rheumatoid arthritis (RA) patients, and to examine the effects of systemic administration of FK228 in an animal model of arthritis. Autoantibody-mediated arthritis (AMA) was induced in 19 male DBA/1 mice (6-7 weeks old); 10 of them were treated by intravenous administration of FK228 (2.5 mg/kg), and 9 were used as controls. The effects of FK228 were examined by radiographic, histologic, and immunohistochemical analyses and arthritis scores. RA synovial fibroblasts (RASFs) were obtained at the time of joint replacement surgery. In vitro effects of FK228 on cell proliferation were assessed by MTT assay. Cell morphology was examined by light and transmission electron microscopy. The effects on the expression of the cell cycle regulators p16INK4a and p21(WAF1/Cip1) were examined by real-time polymerase chain reaction and Western blot analysis. The acetylation status of the promoter regions of p16INK4a and p21(WAF1/Cip1) were determined by chromatin immunoprecipitation assay. A single intravenous injection of FK228 (2.5 mg/ml) successfully inhibited joint swelling, synovial inflammation, and subsequent bone and cartilage destruction in mice with AMA. FK228 treatment induced histone hyperacetylation in the synovial cells and decreased the levels of tumor necrosis factor alpha and interleukin-1beta in the synovial tissues of mice with AMA. FK228 inhibited the in vitro proliferation of RASFs in a dose-dependent manner. Treatment of cells with FK228 induced the expression of p16INK4a and up-regulated the expression of p21(WAF1/Cip1). These effects of FK228 on p16INK4a and p21(WAF1/Cip1) were related to the acetylation of the promoter region of the genes. Our findings strongly suggest that systemic administration of HDA inhibitors may represent a novel therapeutic target in RA by means of cell cycle arrest in RASFs via induction of p16INK4a expression and increase in p21(WAF1/Cip1) expression.

Cooperation of Ras- and c-Myc-dependent pathways in regulating the growth and invasiveness of synovial fibroblasts in rheumatoid arthritis.

To study the specific contribution of MAP kinase activator c-Raf-1 and one of its downstream transcription factors, c-Myc, to the growth and invasive behavior of rheumatoid arthritis synovial fibroblasts (RASFs). RASFs were transduced with retroviral constructs expressing dominant-negative mutants of c-Raf-1 or c-Myc (DN c-Raf-1 or DN c-Myc, respectively) or with the mock vector. The expression of wild-type and mutant proteins was confirmed by Western blotting. Growth curves of RASFs were recorded, and apoptosis was measured by flow cytometry. Invasiveness of RASFs was assessed in the SCID mouse model of RA. Immunohistochemistry was used to study the effects of DN c-Raf-1 on phosphorylated c-Jun and matrix metalloproteinase 1 (MMP-1) in RASFs implanted into SCID mice. The phosphorylation of ERK and JNK in DN c-Raf-1- and mock-transduced RASFs was determined in vitro by Western blotting. The levels of MMPs in these cells were measured by quantitative polymerase chain reaction (PCR). Neither DN c-Raf-1 alone nor DN c-Myc alone significantly altered proliferation or apoptosis of RASFs, but both mutants together rapidly induced apoptosis. Inhibition of c-Raf-1 or c-Myc significantly reduced the invasiveness of RASFs in the SCID mouse model. DN c-Raf-1 decreased the phosphorylation of ERK and JNK in vitro and reduced the in vivo expression of phosphorylated c-Jun as well as the expression of disease-relevant MMPs. As determined by quantitative PCR, the inhibition was most pronounced for MMP-1 and MMP-3. The data demonstrate that Ras- and c-Myc-dependent signaling events cooperate to regulate the growth and invasiveness of RASFs. Targeting of both c-Raf-1 and c-Myc may constitute an interesting therapeutic approach in RA.

Induction of RANKL expression and osteoclast maturation by the binding of fibroblast growth factor 2 to heparan sulfate proteoglycan on rheumatoid synovial fibroblasts.

Rheumatoid arthritis (RA) is characterized by progressive joint destruction. The aim of this study was to clarify the relevance of RA synovial fibroblasts (RASFs) and fibroblast growth factor 2 (FGF-2), which is produced abundantly by RASFs, to the osteoclastogenesis and bone resorption in RA. Synovial fibroblasts were prepared from the synovial tissues of 10 patients with active RA and 7 patients with osteoarthritis (OA). The expression of RANKL, intercellular adhesion molecule 1 (ICAM-1), FGF receptor 1 (FGFR-1), and heparan sulfate proteoglycan (HSPG) on synovial fibroblasts was measured by FACScan. Osteoclast formation in cocultures of RASFs and peripheral blood mononuclear cells (PBMCs) was evaluated by tartrate-resistant acid phosphatase staining and a pit-formation assay using dentin slices. FGF-2 induced the expression of both RANKL and ICAM-1 on RASFs more so than on OA synovial fibroblasts (OASFs). FGF-2-induced up-regulation of RANKL and ICAM-1 was inhibited by anti-FGF-2 antibody. Although FGFR-1 was equally expressed on RASFs and OASFs, HSPG was highly expressed on RASFs. Up-regulation of RANKL by FGF-2 on RASFs was diminished by the removal of heparan sulfate with heparitinase. Osteoclast formation from PBMCs induced by RASFs was inhibited by the addition of either heparitinase, anti-ICAM-1 antibody, anti-FGF-2 antibody, or osteoprotegerin. FGF-2-induced RANKL on RASFs and osteoclast formation were suppressed by an inhibitor of ERK. FGF-2 was transferred to FGFR-1 through binding to HSPG, which is characteristically expressed on RASFs, resulting in RANKL- and ICAM-1-mediated maturation of osteoclasts via ERK activation. Thus, we propose that FGF-2 not only augments the proliferation of RASFs, but also is involved in osteoclast maturation, which leads to bone destruction in RA.

Effect of Triptolide on TNFalpha-induced activation of NF-kappaB and expression of COX-2 and iNOS in human rheumatoid arthritis synovial fibroblasts

To explore the effects of Triptolide (TP) on TNFalpha-induced cell proliferation and expressions of cyclooxygenase-2 (COX-2), inducible nitric oxide synthase (iNOS) and their inducing products PGE2, NO in human rheumatoid arthritis synovial fibroblasts (RASF). Fibroblasts (RASF) were obtained from synovial tissue of patients with RA and were cultured in vitro. RASF were stimulated with TNFalpha(20 microg/L) in the presence or absence of TP(0 - 100 microg/L) for 20 h. The RASF proliferation was determined by (3)H-TdR incorporation, and the productions of PGE2 and NO in culture supernatants of RASF were detected with competitive ELISA and enzyme reduction of nitrate. Expressions of COX-2 and iNOS mRNA in RASF were analyzed by semi-quantitative RT-PCR. Expressions of COX-2 and iNOS protein were estimated by Western-blot method and cellular enzyme immunoassay in synovial fibroblasts. NF-kappaB activity in whole-cell extract of RASF was also measured by an ELISA-based method. TP (>20 microg/L) down-regulated markedly TNFalpha-induced COX-2 and iNOS mRNA and protein expression, and their inducing products PGE2 and NO of synovial fibroblasts. This effect was positively correlated with TP concentrations. NF-kappaB activity in TNFalpha-stimulated synovial cells was suppressed profoundly by TP treatment (IC(50) approximately 35microg/L). The activity of NF-kappaB was correlated with the levels of COX-2 and iNOS expression in TNFalpha-stimulated RASF. No change was observed in proliferation of synovial cells after treatment of TP. TP could significantly down-regulate TNFalpha-induced COX-2, iNOS expression and production of PGE2, NO in human RASF, which is associated with the suppression of NF-kappaB activity.

Induction of apoptosis in rheumatoid synovial fibroblasts by celecoxib, but not by other selective cyclooxygenase 2 inhibitors.

Selective cyclooxygenase 2 (COX-2) inhibitors are now being used as antiinflammatory agents that cause fewer gastrointestinal complications, compared with other antiinflammatory drugs, in patients with rheumatoid arthritis (RA). This study was undertaken to investigate whether selective COX-2 inhibitors could induce apoptosis of RA synovial fibroblasts (RASFs). RASFs were exposed to selective COX-2 inhibitors, i.e., celecoxib, etodolac, meloxicam, nimesulide, N-[2-(cyclohexyloxyl)-4-nitrophenyl]-methanesulfonamide, and rofecoxib, under various conditions. Cell proliferation and cell viability were assessed by incorporation of 5-bromo-2'-deoxyuridine and by the 2-(4-iodophenyl)-3-(4-nitrophenyl)-5-(2,4-disulfophenyl)-2H-tetrazolium monosodium salt assay, respectively. Apoptosis was detected by identifying DNA fragmentation. Activation of peroxisome proliferator-activated receptor gamma (PPARgamma) was measured by the luciferase reporter gene assay with a PPAR response element-driven luciferase reporter plasmid and a PPARgamma expression plasmid. Celecoxib strongly inhibited the proliferation of RASFs, whereas other selective COX-2 inhibitors had little or no effect. In addition, celecoxib reduced the viability of RASFs by induction of apoptosis, in a concentration-dependent manner. This action was abolished by addition of caspase inhibitors. Interleukin-1beta had a weak enhancing effect on celecoxib-induced apoptosis in RASFs. In contrast, other selective COX-2 inhibitors at concentrations up to 100 microM did not induce apoptosis of RASFs. Indomethacin, a nonselective COX inhibitor, activated PPARgamma transcription, while celecoxib did not. Celecoxib suppressed the proliferation of RASFs by COX-2-independent and PPARgamma-independent induction of apoptosis. Although the mechanism involved remains unclear, celecoxib may have not only antiinflammatory activity, but also a disease-modifying effect on rheumatoid synovial proliferation.

Effects of TIMP-1 and TIMP-3 gene transfer on invasiveness, proliferation and apoptosis of rheumatoid arthritis (RA) synovial fibroblasts (RA-SF)

TIMPs play a key role in counter balancing the action of MMPs and have been associated with cell proliferation, inhibition of angiogenesis and induction of apoptosis. Here, we investigated the effects of TIMP-1 and TIMP-3 gene transfer on cartilage invasion, proliferation and apoptosis of RA-SF. RA-SF were transduced with an adenoviral vector expressing human TIMP-1 (AdTIMP-1) or TIMP-3 (AdTIMP-3). Transduction efficacy was assessed by LacZ staining of RA-SF that were transduced with an adenoviral β-galactosidase construct. Untransduced and mock transduced RA-SF were used as controls. TIMP-1 was measured by ELISA in the culture supernatants of AdTIMP-1 transduced and mock transduced cells every 10 days until 60 days after transduction. Proliferation was assessed by 3H-thymidine incorporation, and the rate of spontaneous apoptosis as well as FasL induced cell death was determined by a histon fragmentation assay. AdTIMP-1 and AdTIMP-3 transduced RA-SF and control RA-SF were co-implanted with human articular cartilage under the renal capsule of SCID mice for 60 days and their invasiveness was evaluated on paraffin sections using a semiquantitative score. Transduction efficacy was 67%, and TIMP-1 levels in the supernatants of AdTIMP-1 transduced cells were 51.5 ± 6.5 μg/ml as compared to 8.7 ± 3.4 μg/ml in the mock transduced cells. These levels of TIMP expression were maintained for at least 60 days. AdTIMP-1 and AdTIMP-3 gene transfer resulted in an inhibition of proliferation (35% and 40% vs. mock, respectively; P < 0.05). Transduction of RA-SF with AdTIMP-3 but not TIMP-1 increased spontaneous apoptosis (+24%; vs. mock, P < 0.05) as well as susceptibility to FasL-induced cell death (+23% vs. mock, P < 0.05). In the SCID mouse model, untransduced and mock transduced RA.SF deeply invaded the cartilage (scores: 2.5 ± 0.2 and 3.2 respectively). In the AdTIMP-1 and AdTIMP-3 transduced RA-SF, invasion was inhibited clearly (scores 0.9 ± 0.4 and 1.2 ± 0.2 respectively) Both AdTIMP-1 and AdTIMP-3 gene transfer inhibit proliferation of RA-SF and reduce cartilage invasion. In contrast to TIMP-1, adenoviral gene transfer with TIMP-3. has a strong pro-apoptotic effect on RA-SF and facilitates Fas mediated cell death. These results indicate that gene transfer of TIMPs may be a useful approach to inhibit joint destruction in RA.