Jinwu Jiangu Capsule affects synovial cells in rheumatoid arthritis through PI3K/Akt/mTOR signaling pathway.

Jinwu Jiangu Capsule is a medicinal formula from the Chinese Miao nationality. Leflunomide is recommended in organizational guidelines for the treatment of rheumatoid arthritis (RA). To investigate the effect of Jinwu Jiangu Capsule on PI3K/Akt/mTOR signal pathway in cells taken from RA patients New Zealand rabbits were administrated with Jinwu Jiangu Capsule suspension to prepare serum containing medicine. Lyophilized powder was prepared from this serum for cell treatment. The expression of LC3-II and PI3K, AKT, mTOR were detected by IF and western blot. Moreover, the levels of Atg1, Atg5, Atg14 were detected by RT-qPCR. The results showed that the expression of LC3-II was increased, and fluorescence spot of LC3-II was obvious in high-dose of Jinwu Jiangu Capsule group. Jinwu Jiangu Capsule decreased the level of PI3k, Akt, and mTOR protein, and increased the levels of Atg1, Atg5 and Atg14. Specially, the high-dose of Jinwu Jiangu Capsule had the most obvious inhibitory and up-regulation effects. However, there was no significant difference in the expression of Akt, mTOR and Atg1 in the medium-dose of Jinwu Jiangu Capsule group compared with the leflunomide group. In conclusion, Jinwu Jiangu Capsule regulates autophagy by inhibiting the PI3K/AKT/mTOR pathway in RA.

[Pharmacodynamic mechanism of modified Ganlu Yaoyu San intreatment of rheumatoid arthritis based on MAPK signaling pathway].

According to the findings, modified Ganlu Yaoyu San has a good anti-inflammatory activity, and can significantly alleviate the degree of arthritis. Its therapeutic effect for rheumatoid arthritis may be related to the regulation of MAPK pathway of synovial cells. In the study, the rat adjuvant arthritis(AA) model was established to further investigate the pharmacodynamic mechanism for regulating MAPK pathway of synovial cells. Enzyme-linked immune assay was used to determine the serum TNF-α level of AA rats administered with drug for two weeks, synovial tissue protein kinases ERK1/2 and p38 content were determined by immunohistochemistry, synovial tissue JNK1, ERK1, p38 gene(mRNA) expression were detected with fluorescence quantitative PCR(RT-PCR) method. According to the results, after administration for two weeks, the levels of serum TNF-α of AA rat was significantly decreased(P<0.05). After administration for four weeks, the protein expressions of p38 and ERK1/2 in synovial tissue were reduced(P<0.05 or P<0.01), the gene expressions of JNK1, p38 and ERK1 in knee joint synovial tissue were reduced(P<0.05 or P<0.01). In conclusion, modified Ganlu Yaoyu San can effectively treat rheumatoid arthritis. Its mechanism might be related to the reduction of TNF-α levels in serum, protein expression of p38 and ERK1/2 in synovial tissue, and JNK1, p38 and ERK1 gene expressions, and regulation of MAPK pathway.

ß-Elemene induces apoptosis of human rheumatoid arthritis fibroblast-like synoviocytes via reactive oxygen species-dependent activation of p38 mitogen-activated protein kinase.

BACKGROUND: ß-Elemene is a natural anticancer compound extracted from the Chinese medicinal herb Curcuma Wenyujin. This study was done to determine the effect of ß-elemene on the apoptosis of rheumatoid arthritis fibroblast-like synoviocytes (RA-FLS) and associated molecular mechanisms. METHODS: RA-FLS were treated for 72h with ß-elemene at 10-200µg/ml and cell viability and apoptotic changes were examined. The involvement of reactive oxygen species (ROS) and mitogen-activated protein kinases (MAPKs) was checked. RESULTS: We found that ß-elemene significantly inhibited the viability and promoted apoptosis of RA-FLS in a concentration-dependent fashion. ß-Elemene-treated FLS showed a significant decline in mitochondrial membrane potential, an accumulation of cytochrome c in the cytosol, and increased activities of caspase-9 and caspase-3. ß-Elemene treatment caused an enhancement of p38 MAPK phosphorylation and ROS production. The pro-apoptotic activity of ß-elemene was significantly reversed by pretreatment with the p38 inhibitor SB203580 or ROS inhibitor N-acetyl-l-cysteine. CONCLUSIONS: Taken together, ß-elemene is effective in inducing mitochondrial apoptosis of RA-FLS, which is mediated through induction of ROS formation and p38 MAPK activation. ß-Elemene may thus have therapeutic benefits for RA.

Expression of peptidylarginine deiminase 4 and protein tyrosine phosphatase nonreceptor type 22 in the synovium of collagen-induced arthritis rats.

OBJECTIVE: To study the expression level of peptidylarginine deiminase 4 (PADI4) and protein tyrosine phosphatase nonreceptor type 22 (PTPN22) in the synovium of rat model of collagen-induced arthritis, and to explore their possible therapeutic role in rheumatoid arthritis. METHODS: Thirty-two female Wistar rats weighing 100±20 g were randomly assigned into 3-week collagen-induced arthritis (CIA) model group (n=8), 4-week CIA model group (n=8), 6-week CIA model group (n=8), and the control group (n=8). The body weight changes of each group were recorded. The expression levels of PADI4 and PTPN22 were detected and compared by the methods of immunohistochemical staining and Western blot. RESULTS: Arthritis of rat began to form 14 days after sensitization and the joint swelling reached peak at 28 days. The weights of the rats slowly grew both in CIA model groups and the control group. Immunohistochemical staining results showed that the positive expression of PADI4 and PTPN22 was mainly located in cartilage peripheral mononuclear cells, the cytoplasm of infiltrated cells, and bone marrow cavity. There were significant differences in the optical density of PADI4 and PTPN22 among CIA model groups and the control group (PADI4, 0.2898±0.012, 0.2982±0.022, 0.2974±0.031, 0.2530±0.013 in 3-week CIA model, 4-week CIA model, 6-week CIA model and control groups; PTPN22, 0.2723±0.004, 0.2781±0.010, 0.2767±0.008, 0.2422±0.019; all P <0.05). The expression bands of PADI4 were observed in Western blot 3 weeks after initial immunization, the thickest in the 4th week, and decreased in the 6th week. The expression bands of PTPN2 were observed at all the time points, with no obvious time-dependent trend. CONCLUSIONS: PADI4 and PTPN22 are obviously correlated with CIA in rat model. PADI4 is expressed at early stage of the disease, while the expression of PTPN22 sustains throughout the course.

Metabolic regulatory and anti-oxidative effects of modified Bushen Huoxue decoction on experimental rabbit model of osteoarthritis.

OBJECTIVE: To observe the metabolic, regulatory and anti-oxidative effects of modified Bushen Huoxue Decoction (BSHXD), a Chinese herbal medicine for kidney (Shen)-reinforcement and blood-activation, on an osteoarthritis (OA) rabbit model. METHODS: A rabbit model for knee joint OA was established by the classic Hulth's method. The OA model rabbits were randomized into 5 groups: the model control group, the positive control group treated with glucosamine sulfate, and the three BSHXD treated groups treated respectively with low, moderate, and high doses of BSHXD. In addition, a normal control group and a sham-operated group were set up. Experimental animals were sacrificed after a 7-week treatment, and pathological changes in cartilaginous tissue were estimated using the Mankin criteria. Hydroxyproline (Hyp) and malonaldehyde (MDA) contents in blood serum and urine, as well as superoxide dismutase (SOD) activity and nitric oxide (NO) content in blood serum and knee joint synovial homogenates were detected. RESULTS: Mankin scoring showed insignificant statistical differences between the various treatment groups (P >0.05), but all were better than the model control group (P <0.05). Serum and urinary contents of Hyp and MDA as well as serum and synovial levels of NO were significantly lower, but the SOD activity in blood serum and synovial tissue was higher in the BSHXD treated groups than in the model group P <0.01); the effect of BSHXD was dose-dependent to some extent. CONCLUSION: The modified BSHXD shows an effect of improving cartilage metabolism in experimental rabbits with OA, and possesses osteo-chondric protective effects in antagonizing peroxidation injury.

Paeoniflorin inhibits proliferation of fibroblast-like synoviocytes through suppressing G-protein-coupled receptor kinase 2.

Paeoniflorin (Pae) is a monoterpene glucoside and the main component of the total glucosides of paeony (TGP) extracted from the roots of Paeonia lactiflora. Its anti-inflammatory effect is associated with regulating G-protein-coupled receptors (GPCRs) signaling. The aim of this study was to explore the expression change of G-protein-coupled receptor kinase 2 (GRK2) in fibroblast-like synoviocytes (FLS) and the effect of Pae. Pae was obtained and purified from the roots of Paeonia lactiflora. We investigated the expression of GRK2 in synovium during the inflammatory process and assessed the effects of a specific GRK2 inhibitor and Pae on proliferation, cAMP level, and protein kinase A (PKA) activity of FLS in vitro. Additionally, the effect of Pae on GRK2 expression in FLS was detected in vitro. Expression of GRK2 in synovium from CIA rats increased during the inflammatory process. The specific GRK2 inhibitor suppressed proliferation and increased the cAMP level as well as PKA activity of FLS, and Pae had the same effects. Furthermore, Pae decreased GRK2 expression in FLS in vitro. Our results indicate that a chronic inflammatory process in CIA induces upregulation of GRK2 expression in FLS, and Pae can reverse this change, which might be one of the important mechanisms for Pae regulating GPCRs signaling and suppressing the proliferation of FLS in CIA.

Inhibition of epidermal growth factor receptor tyrosine kinase ameliorates collagen-induced arthritis.

Rheumatoid arthritis (RA) is an autoimmune synovitis characterized by the formation of pannus and the destruction of cartilage and bone in the synovial joints. Although immune cells, which infiltrate the pannus and promote inflammation, play a prominent role in the pathogenesis of RA, other cell types also contribute. Proliferation of synovial fibroblasts, for example, underlies the formation of the pannus, while proliferation of endothelial cells results in neovascularization, which supports the growth of the pannus by supplying it with nutrients and oxygen. The synovial fibroblasts also promote inflammation in the synovium by producing cytokines and chemokines. Finally, osteoclasts cause the destruction of bone. In this study, we show that erlotinib, an inhibitor of the tyrosine kinase epidermal growth factor receptor (EGFR), reduces the severity of established collagen-induced arthritis, a mouse model of RA, and that it does so by targeting synovial fibroblasts, endothelial cells, and osteoclasts. Erlotinib-induced attenuation of autoimmune arthritis was associated with a reduction in number of osteoclasts and blood vessels, and erlotinib inhibited the formation of murine osteoclasts and the proliferation of human endothelial cells in vitro. Erlotinib also inhibited the proliferation and cytokine production of human synovial fibroblasts in vitro. Moreover, EGFR was highly expressed and activated in the synovium of mice with collagen-induced arthritis and patients with RA. Taken together, these findings suggest that EGFR plays a central role in the pathogenesis of RA and that EGFR inhibition may provide benefits in the treatment of RA.

Anti-inflammatory effects of Clematis chinensis Osbeck extract(AR-6) may be associated with NF-κB, TNF-α, and COX-2 in collagen-induced arthritis in rat.

The root of Clematis chinensis Osbeck has been used widely in rheumatoid arthritis in Chinese traditional medicine, and AR-6 is a triterpene saponin isolated from it. In this present study, we investigated the in vivo effects of oral AR-6 in chronic rat with collagen-induced arthritis (CIA) and possible molecular mechanism. CIA was induced by immunizing 56 female Sprague-Dawley (SD) rats with chicken typeIIcollagen (CII). Following eighteen days, the immunization rats with CIA were treated with AR-6 (32, 16, 8 mg/kg), cyclophosphamide (7 mg/kg), and TGP (Total Glucosides of Paeonia) (180 mg/kg) for 7 days, and rats without CIA were given the same volume of purified water. TNF-α and IL-1ß levels in peripheral blood will be measured by ELISA, and Western blot analysis will be used to detect the expression of NF-κB p65 subunits, TNF-α and COX-2, in synovial membrane. We found that therapeutic treatment with AR-6 markedly improves the paw swelling and histopathological changes. Moreover, the serum levels of pro-inflammatory cytokines TNF-α and IL-1ß were markedly lowered, and the expression of NF-κB p65 subunits, TNF-α and COX-2, in the synovial membrane of CIA rats was significantly inhibited in the AR-6-treated groups. These results enable to prove that AR-6 has a potential anti-inflammatory effect in CIA rats, and its mechanism may relate to the inhibition of the expression of NF-κB p65 subunits, TNF-α and COX-2.

[Effects of acupuncture on the number and degranulation ratio of mast cells and expression of tryptase in synovium of rats with adjuvant arthritis].

OBJECTIVE: To observe the effects of acupuncture on synovial pathology, synovial mast cell degranulation and tryptase expression and to investigate the relationship between the functions of mast cells and effects of acupuncture on early adjuvant arthritis in rats. METHODS: Forty-six male Wistar rats were randomly divided into normal control group (n=16), untreated group (n=15) and acupuncture group (n=15). Adjuvant arthritis was induced by injection of 0.1 mL Freund's complete adjuvant in right hind limb footpad. Normal control group and untreated group received no acupuncture treatment, while rats in the acupuncture group were treated with sterilized disposable stainless steel needles inserted perpendicularly as deep as 2 to 3 mm at Xuanzhong (GB39), 6 mm at Shenshu (BL23) and 7 mm at Zusanli (ST36) for eight times (15 min each time) every two days. Setting the modeling day as the 0 day of the experiment, the body weight and paw volume of the rats were measured every three days from the 0 day. In the end, synovial tissues of the right hind ankles were sampled and made into paraffin sections. Then they were firstly stained with hematoxylin-eosin for observing synovial pathology to evaluate the effects of acupuncture on adjuvant arthritis, then stained with toluidine blue for observing the number and degranulation ratio of synovial mast cells and finally detected by immunohistochemical staining method to investigate the expression of tryptase in synovium. RESULTS: Compared with the untreated group, the body weight of rats in the acupuncture group was increased significantly (P<0.05), while the paw volume decreased obviously (P<0.01). Hematoxylin-eosin staining showed that acupuncture significantly inhibited inflammatory cell infiltration, synovial cell hyperplasia, and synovial fibroplasia in synovium of rats with adjuvant arthritis as compared with the untreated group (P<0.05). Toluidine blue staining showed that acupuncture could significantly diminish the numbers of total and degranulated mast cells in rats with adjuvant arthritis (P<0.01), which were significantly higher in the untreated group than in the normal control group (P<0.01). Showing by immunohistochemical staining, the expression of tryptase in synovium in the acupuncture group was decreased as compared with the untreated group (P<0.01). Analyzed by Spearman's bivariate correlation, the number of mast cells and degranulation ratio of mast cells were positively correlated with the pathological scores (r=0.837, P<0.01; r=0.634, P<0.01). CONCLUSION: Acupuncture can improve pathological condition of inflammatory synovium in rats with early adjuvant arthritis by inhibiting the function of synovial mast cells, which may play an important underlying role in the immunoregulation of acupuncture on adjuvant arthritis.

Effect of the oral application of a highly selective MMP-13 inhibitor in three different animal models of rheumatoid arthritis.

OBJECTIVE: To evaluate the decrease of cartilage destruction by a novel orally active and specific matrix metalloproteinase 13 (MMP-13) inhibitor in three different animal models of rheumatoid arthritis (RA). MATERIALS AND METHODS: The SCID mouse co-implantation model of RA, the collagen-induced arthritis (CIA) model in mice and the antigen-induced arthritis model (AIA) in rabbits were used. RESULTS: In the SCID mouse co-implantation model, the MMP-13 inhibitor reduced cartilage destruction by 75%. In the CIA model of RA, the MMP-13 inhibitor resulted in a significant and dose-dependent decrease in clinical symptoms as well as of cartilage erosion by 38% (30 mg/kg), 28% (10 mg/kg) and 21% (3 mg/kg). No significant effects were seen in the AIA model. No toxic effects were seen in all three animal models. CONCLUSION: Although several MMPs in concert with other proteinases have a role in the process of cartilage destruction, there is a need for highly selective MMP inhibitors to reduce severe side effects that occur with non-specific inhibitors. Significant inhibition of MMP-13 reduced cartilage erosions in two of three tested animal models of RA. These results strongly support the development of this class of drugs to reduce or halt joint destruction in patients with RA.

Expression of 5-lipoxygenase and 15-lipoxygenase in rheumatoid arthritis synovium and effects of intraarticular glucocorticoids.

INTRODUCTION: It was previously shown that lipoxygenase (LO) pathways are important in the rheumatoid arthritis (RA) inflammatory process and that synovial fluid from RA patients contains high amounts of leukotrienes. We therefore aimed to investigate the 5-LO and 15-LO-1 expression pattern in RA and ostheoarthritis (OA) synovial tissue and to study the effect of intraarticular glucocorticoid (GC) therapy on enzyme expression. METHODS: Expression of LOs was evaluated by immunohistochemistry in RA and OA synovial biopsies. Cellular localization of these enzymes was analyzed by double immunofluorescence. In synovial biopsies from 11 RA patients, 5-LO and 15-LO-1 expression was evaluated before and after triamcinolone hexacetonide knee injection and assessed by image analysis to quantify their expression. We also investigated the presence of 15-LO-1 by immunohistochemistry in synovial fluid (SF) cells as well as their ability to form 15-hydroxyeicosatetraenoic acid (15-HETE) following treatment with arachidonic acid (AA). RESULTS: 5-LO and 15-LO-1 are present in RA and OA synovium, with 5-LO being mostly expressed in lining and sublining macrophages, neutrophils and mast cells and 15-LO-1 mainly in lining macrophages, fibroblasts and sublining endothelial cells. Intraarticular GC treatment resulted in a significant suppression of 5-LO expression, but did not influence the 15-LO-1 enzyme significantly. Also, SF cells express a functional 15-LO-1 and produce 15-HETE when challenged with AA. CONCLUSIONS: These data demonstrate that local therapy with GC decreases 5-LO expression in RA synovium and offer an additional possible mechanism for the efficiency of intraarticular adjuvant therapy in RA.

Cordycepin inhibits IL-1beta-induced MMP-1 and MMP-3 expression in rheumatoid arthritis synovial fibroblasts.

OBJECTIVE: MMP is a key enzyme in the degradation of extracellular matrices, and its expression plays important roles in inflammatory diseases. Cordycepin (3'-deoxyadenosine), a bioactive compound of Cordyceps militaris, has been shown to exhibit many pharmacological activities, such as anti-cancer, anti-inflammatory and anti-infection activities. In this study, we aimed at the inhibitory effect of cordycepin on IL-1beta-induced MMP-1 and MMP-3 expression as well as the molecular basis using RA synovial fibroblasts (RASFs). METHODS: RASFs were isolated from synovial tissue obtained from 12 patients with RA and cultured in monolayer. Expression of MMP-1 and MMP-3 was evaluated using western blotting and real-time PCR. Chemokines were analysed by ELISA. The phosphorylation of mitogen-activated protein kinase was measured by western blotting. Electrophoretic mobility shift assay was performed to evaluate binding activities of DNA to nuclear factor-kappaB (NF-kappaB) and activator protein-1 (AP-1). RESULTS: Cordycepin inhibited IL-1beta-induced MMP-1 and MMP-3 expressions in RASFs in a dose-dependent manner. Among various chemokines [such as monocyte chemoattractant protein-1 (MCP-1), GRO-alpha, regulated upon activation, normal T-cell expressed and presumably secreted (RANTES) and epithelial neutrophil activating peptide 78 (ENA-78)], cordycepin specifically blocked IL-1beta-induced ENA-78 production in RASF. Moreover, cordycepin significantly inhibited IL-1beta-induced p38/JNK and AP-1 activation, but not extracellular signal-regulated kinase (ERK) and NF-kappaB activation. CONCLUSIONS: Cordycepin is a potent inhibitor of IL-1beta-induced chemokine production and MMP expression and strongly blocks the p38/JNK/AP-1 signalling pathway in RASFs.

Inhibition of cyclooxygenase 2 expression by diallyl sulfide on joint inflammation induced by urate crystal and IL-1beta.

OBJECTIVE: Investigation of the effects of diallyl sulfide (DAS), a garlic sulfur compound, on joint tissue inflammatory responses induced by monosodium urate (MSU) crystals and interleukin-1beta (IL-1beta). DESIGN: The HIG-82 synovial cell line was used to establish the experimental model and DAS regime. Primary cultures of articular chondrocytes and synovial fibroblasts obtained from patients undergoing joint replacement for osteoarthritis were used in experimental studies. Cyclooxygenase (COX) expression following MSU crystal and IL-1beta stimulation with/without DAS co-incubation was assessed by reverse transcription-polymerase chain reaction (RT-PCR), western blotting, and immunocytochemistry and nuclear factor-kappa B (NF-kappaB) activation determined by electrophoretic mobility shift assay. Prostaglandin E2 (PGE(2)) production was measured by enzyme-linked immunosorbent assay (ELISA). DAS effects on COX gene expression in an MSU crystal-induced acute arthritis in rats were assessed by RT-PCR. RESULTS: MSU crystals upregulated COX-2 expression in HIG-82 cells and this was inhibited by co-incubation with DAS. DAS inhibited MSU crystal and IL-1beta induced elevation of COX-2 expression in primary synovial cells and chondrocytes. Production of PGE(2) induced by crystals was suppressed by DAS and celecoxib. MSU crystals had no effect on expression of COX-1 in synovial cells. NF-kappaB was activated by MSU crystals and this was blocked by DAS. Increased expression of COX-2 in synovium following intraarticular injection of MSU crystals in a rat model was inhibited by co-administration of DAS. CONCLUSIONS: DAS prevents IL-1beta and MSU crystal induced COX-2 upregulation in synovial cells and chondrocytes and ameliorates crystal induced synovitis potentially through a mechanism involving NF-kappaB. Anti-inflammatory actions of DAS may be of value in treatment of joint inflammation.

Restorative and synergistic efficacy of Kalpaamruthaa, a modified Siddha preparation, on an altered antioxidant status in adjuvant induced arthritic rat model.

BACKGROUND: Rheumatoid arthritis (RA) is a prevalent and debilitating disease that affects the joints. Infiltration of blood-derived cells in the affected joints upon activation generate reactive oxygen/nitrogen species, resulting in an oxidative stress. One approach to counteract this oxidative stress is the use of antioxidants as therapeutic agents. OBJECTIVES: Kalpaamruthaa (KA), a modified indigenous Siddha preparation constituting Semecarpus anacardium nut milk extract (SA), Emblica officinalis (EO) and honey was evaluated for its synergistic antioxidant potential in adjuvant induced arthritic rats than sole SA treatment. MATERIALS AND METHODS: Levels/activities of reactive oxygen species (ROS)/reactive nitrogen species (RNS), myeloperoxidase, lipid peroxide and enzymic and non-enzymic antioxidants were determined in control, arthritis induced, SA and KA treated (150 mg/kg b.wt.) animals. RESULTS AND CONCLUSION: The levels/activities of ROS/RNS, myeloperoxidase and lipid peroxide were increased significantly (p<0.05) and the activities of enzymic and non-enzymic antioxidants were in turn decreased in arthritic rats, whereas these changes were reverted to near normal levels upon SA and KA treatment. KA showed an enhanced antioxidant potential than sole treatment of SA in adjuvant induced arthritic rats. KA via enhancing the antioxidant status in adjuvant induced arthritic rats than sole SA treatment proves to be an important therapeutic modality in the management of RA and thereby instituting the role of oxidative stress in the clinical manifestation of the disease RA. The profound antioxidant efficacy of KA than SA alone might be due to the synergistic action of the polyphenols such as flavonoids, tannins and other compounds such as vitamin C and hydroxycinnamates present in KA.

Calcineurin is expressed and plays a critical role in inflammatory arthritis.

Calcineurin is a calcium-activated phosphatase to mediate lymphocyte activation and neuron signaling, but its role in inflammatory arthritis remains largely unknown. In this study, we demonstrate that calcineurin was highly expressed in the lining layer, infiltrating leukocytes, and endothelial cells of rheumatoid synovium. The basal expression levels of calcineurin were higher in the cultured synoviocytes of rheumatoid arthritis patients than those of osteoarthritis patients. The calcineurin activity in the synoviocytes was increased by the stimulation with proinflammatory cytokines such as IL-1beta and TNF-alpha. Moreover, rheumatoid arthritis synoviocytes had an enlarged intracellular Ca(2+) store and showed a higher degree of [Ca(2+)](i) release for calcineurin activity than osteoarthritis synoviocytes when stimulated with either TNF-alpha or phorbol myristate acetate. IL-10, an anti-inflammatory cytokine, failed to increase the Ca(2+) and calcineurin activity. The targeted inhibition of calcineurin by the overexpression of calcineurin-binding protein 1, a natural calcineurin antagonist, inhibited the production of IL-6 and matrix metalloproteinase-2 by rheumatoid synoviocytes in a similar manner to the calcineurin inhibitor, cyclosporin A. Moreover, the abundant calcineurin expression was found in the invading pannus in the joints of mice with collagen-induced arthritis. In these mice, calcineurin activity in the cultured synovial and lymph node cells correlated well with the severity of arthritis, but which was suppressed by cyclosporin A treatment. Taken together, our data suggest that the abnormal activation of Ca(2+) and calcineurin in the synoviocytes may contribute to the pathogenesis of chronic arthritis and thus provide a potential target for controlling inflammatory arthritis.

Tumour necrosis factor activates the mitogen-activated protein kinases p38alpha and ERK in the synovial membrane in vivo.

Tumour necrosis factor (TNF) is considered to be a major factor in chronic synovial inflammation and is an inducer of mitogen-activated protein kinase (MAPK) signalling. In the present study we investigated the ability of TNF to activate MAPKs in the synovial membrane in vivo. We studied human TNF transgenic mice--an in vivo model of TNF-induced arthritis--to examine phosphorylation of extracellular signal-regulated kinase (ERK), c-Jun amino terminal kinase (JNK) and p38MAPKalpha in the inflamed joints by means of immunoblot and immunohistochemistry. In addition, the effects of systemic blockade of TNF, IL-1 and receptor activator of nuclear factor-kappaB (RANK) ligand on the activation of MAPKs were assessed. In vivo, overexpression of TNF induced activation of p38MAPKalpha and ERK in the synovial membrane, whereas activation of JNK was less pronounced and rarely observed on immunohistochemical analysis. Activated p38MAPKalpha was predominantly found in synovial macrophages, whereas ERK activation was present in both synovial macrophages and fibroblasts. T and B lymphocytes did not exhibit major activation of any of the three MAPKs. Systemic blockade of TNF reduced activation of p38MAPKalpha and ERK, whereas inhibition of IL-1 only affected p38MAPKalpha and blockade of RANK ligand did not result in any decrease in MAPK activation in the synovial membrane. These data indicate that TNF preferentially activates p38MAPKalpha and ERK in synovial membrane exposed to TNF. This not only suggests that targeted inhibition of p38MAPKalpha and ERK is a feasible strategy for blocking TNF-mediated effects on joints, but it also shows that even currently available methods to block TNF effectively reduce activation of these two MAPKs.

Inactivation of xanthine oxidoreductase is associated with increased joint swelling and nitrotyrosine formation in acute antigen-induced arthritis.

OBJECTIVE: Arthritis is associated with increased articular formation of nitrotyrosine, which may contribute to injury. Nitrotyrosine is formed by nitration of tyrosine by reactive nitrogen species such as peroxynitrite, the formation of which may be enhanced by xanthine oxidoreductase (XOR), since it can generate nitric oxide from nitrite/nitrate, and superoxide during xanthine metabolism. We hypothesized that inactivation of XOR would protect against antigen-induced arthritis (AIA) and decrease nitrotyrosine formation. METHODS: AIA was induced with methylated bovine serum albumin (mBSA) in three groups of Wistar rats: animals fed on (1) tungsten-enriched chow (0.7 g/kg) (TG), which inactivates XOR, (2) standard chow (SG), and (3) rats treated with allopurinol (50 mg/kg/day; p.o.) (AG). Nitrotyrosine in patella-synovium was quantified by mass spectrometry three weeks after intra-articular (i.a.) antigen injection. RESULTS: Treatment with tungsten, but not allopurinol, suppressed plasma and articular XOR activity at < or = 0.9% of normal levels. XOR inactivation was associated with increased knee swelling 24-48 hrs post i.a. mBSA, compared with controls (mean increase +/- SEM of knee diameter from baseline of 3.3 +/- 0.5, 2.0 +/- 0.3 and 1.9 +/- 0.2 mm in TG, SG and AG (n = 14 each group), respectively; p < 0.05, TG vs SG, ANOVA). Mean ratio of articular nitrotyrosine-tyrosine (+/- SEM) was increased in the XOR-inactivated group, compared with controls: 12.3 +/- 0.7, 9.6 +/- 0.8 and 10.4 +/- 0.5 pg/microg in TG, SG and AG, respectively; p < 0.05, TG vs SG. CONCLUSION: Contrary to expectation, XOR inactivation was associated with increased joint swelling and articular tyrosine nitration in acute AIA, suggesting a novel, protective role for XOR in inflammatory arthritis.

Diosgenin, a plant steroid, induces apoptosis in human rheumatoid arthritis synoviocytes with cyclooxygenase-2 overexpression.

In the present study, we have shown for the first time that a plant steroid, diosgenin, causes an inhibition of the growth of fibroblast-like synoviocytes from human rheumatoid arthritis, with apoptosis induction associated with cyclooxygenase-2 (COX-2) up-regulation. Celecoxib, a selective COX-2 inhibitor, provoked a large decrease in diosgenin-induced apoptosis even in the presence of exogenous prostaglandin E2, whereas interleukin-1beta, a COX-2 inducer, strongly increased diosgenin-induced apoptosis of these synoviocytes. These findings suggest that the proapoptotic effect of diosgenin is associated with overexpression of COX-2 correlated with overproduction of endogenous prostaglandin E2. We also observed a loss of mitochondrial membrane potential, caspase-3 activation, and DNA fragmentation after diosgenin treatment.

Tie2 receptor tyrosine kinase, a major mediator of tumor necrosis factor alpha-induced angiogenesis in rheumatoid arthritis.

OBJECTIVE: Rheumatoid arthritis (RA) is an inflammatory disease and an angiogenic disease. However, the molecular mechanisms promoting angiogenesis in RA are not clearly identified. Our objective was to study the role of an endothelium-specific receptor tyrosine kinase, Tie2, in angiogenesis of inflammatory arthritis. METHODS: Expression of Tie2 and its ligand, angiopoietin 1 (Ang1), in human synovium was examined by immunohistochemistry and Western blot. A novel synovium vascular window model was established to study the role of Tie2 in angiogenesis in vivo. Primary cultured endothelial cells and synoviocytes were used to study tumor necrosis factor alpha (TNF alpha)-induced Tie2 and Ang1 expression. RESULTS: Tie2 was implicated in pathologic angiogenesis. We observed that Tie2 and Ang1 were elevated in human RA synovium. Using a novel collagen-induced arthritis synovial window model, we demonstrated that Tie2 signaling regulated arthritis angiogenesis in vivo. We also showed that Tie2 mediated TNF alpha-induced angiogenesis in a mouse cornea assay. In addition, we observed that TNF alpha can regulate Tie2 activation in multiple ways that may involve interactions between endothelial cells and synoviocytes. TNF alpha up-regulates Tie2 in endothelial cells through nuclear factor kappa B, and it up-regulates Ang1 in synoviocytes. These findings suggest paracrine regulation of angiogenesis between endothelial cells and synoviocytes. CONCLUSION: This study demonstrates that Tie2 regulates angiogenesis in inflammatory synovium. Tie2 signaling is an important angiogenic mediator that links the proinflammatory cytokine TNF alpha to pathologic angiogenesis.

Citrullination of synovial proteins in murine models of rheumatoid arthritis.

OBJECTIVE: Antibodies directed to citrulline-containing proteins are highly specific for rheumatoid arthritis (RA) and can be detected in up to 80% of patients with RA. Citrulline is a nonstandard amino acid that can be incorporated into proteins only by posttranslational modification of arginine by peptidylarginine deiminase (PAD) enzymes. The objective of this study was to investigate the presence of anticitrulline antibodies, PAD enzymes, and citrullinated antigens in mouse models of both acute and chronic destructive arthritis: streptococcal cell wall (SCW)-induced arthritis and collagen-induced arthritis (CIA), respectively. METHODS: Synovial tissue biopsy specimens were obtained from naive mice, mice with CIA, and mice with SCW-induced arthritis. The expression of messenger RNA (mRNA) for PAD enzymes was analyzed by reverse transcriptase-polymerase chain reaction; the presence of PAD proteins and their products (citrullinated proteins) was analyzed by Western blotting and by immunolocalization. The presence of anticitrullinated protein antibodies was investigated by an anti-cyclic citrullinated peptide (anti-CCP) enzyme-linked immunosorbent assay (ELISA) and an ELISA using in vitro citrullinated fibrinogen. RESULTS: In both mouse models, PAD type 2 (PAD2) mRNA was present in the synovium but was not translated into PAD2 protein. In contrast, PAD4 mRNA, although absent from healthy synovium, was readily transcribed and translated by polymorphonuclear neutrophils infiltrating the synovial tissue during inflammation. As a consequence, several synovial proteins were subjected to citrullination. One of these proteins was identified as fibrin, which has been reported to be citrullinated also in synovium of patients with RA. Although generation of citrullinated antigens during synovial inflammation in the mice was eminent, no anti-CCP antibodies could be detected. CONCLUSION: Citrullination of synovial antigens is an active process during joint inflammation in both mice and humans, but the induction of autoantibodies directed to these proteins is a more specific phenomenon, detectable only in human RA patients.