Dexamethasone inhibits BAFF expression in fibroblast-like synoviocytes from patients with rheumatoid arthritis

Fibroblast-like synoviocytes (FLS) play a major role in the pathogenesis of rheumatoid arthritis (RA). FLS isolated from patients with RA (FLS-RA) express B cell-activating factor belonging to the TNF family (BAFF), a cytokine that has been associated with the onset and progression of RA. Glucocorticoids are powerful anti-inflammatory drugs used in the treatment of RA. In the present study, we examined the effect of dexamethasone (Dex) on constitutive and TNF-alpha- and IFN-gamma-induced BAFF expression in FLS-RA. BAFF mRNA expression and soluble BAFF were determined by RT-PCR and ELISA, respectively. The results showed that constitutive BAFF mRNA expression was inhibited by Dex in a dose- and time-dependent manner. Also, Dex inhibited the secretion of BAFF in a time-dependent manner reaching 76% of inhibition 72 h after treatment. Moreover, Dex suppressed both mRNA and protein BAFF expression induced by TNF-alpha but had no effect on IFN-gamma-induced BAFF expression. In comparison with B cells cultured alone, B cells co-cultured with FLS-RA exhibited a higher survival, which was inhibited when FLS-RA were pretreated with Dex. However, the enhanced B cell survival was reestablished by the addition of rhBAFF. Therefore, Dex is a potent inhibitor of constitutive and TNF-alpha-induced BAFF expression in FLS-RA.     

Atorvastatin inhibits osteoclastogenesis by decreasing the expression of RANKL in the synoviocytes of rheumatoid arthritis

IL-17 and related cytokines are direct and indirect targets of selective immunosuppressive agents for the treatment of autoimmune diseases and other diseases of pathologic inflammation. Insights into the potential adverse effects of IL-17 blockade can be drawn from the experience of patients with deficiencies in the IL-17 pathway. A unifying theme of susceptibility to mucocutaneous candidiasis is seen in both mice and humans with a variety of genetic defects that converge on this pathway. Mucocutaneous candidiasis is a superficial infection of mucosal, nail or skin surfaces usually caused by the fungal pathogen Candida albicans. The morbidity of the disease includes significant pain, weight loss and secondary complications, including carcinoma and aneurysms. This review describes the known human diseases associated with chronic mucocutaneous candidiasis (CMC) as well as the known and proposed connections to IL-17 signaling. The human diseases include defects in IL-17 signaling due to autoantibodies (AIRE deficiency), receptor mutations (IL-17 receptor mutations) or mutations in the cytokine genes (IL17F and IL17A). Hyper-IgE syndrome is characterized by elevated serum IgE, dermatitis and recurrent infections, including CMC due to impaired generation of IL-17-producing Th17 cells. Mutations in STAT1, IL12B and IL12RB1 result in CMC secondary to decreased IL-17 production through different mechanisms. Dectin-1 defects and CARD9 defects result in susceptibility to C. albicans because of impaired host recognition of the pathogen and subsequent impaired generation of IL-17-producing T cells. Thus, recent discoveries of genetic predisposition to CMC have driven the recognition of the role of IL-17 in protection from mucosal fungal infection and should guide counseling and management of patients treated with pharmacologic IL-17 blockade.     

Chemerin activates fibroblast-like synoviocytes in patients with rheumatoid arthritis

Introduction

Chemerin is a chemotactic agonist identified as a ligand for ChemR23 that is expressed on macrophages and dendritic cells (DCs). In this study, we analyzed the expression of chemerin and ChemR23 in the synovium of rheumatoid arthritis (RA) patients and the stimulatory effects of chemerin on fibroblast-like synoviocytes (FLSs) from RA patients.

Methods

Chemerin and ChemR23 expression in the RA synovium was ascertained by immunohistochemistry and Western blot analysis. Chemerin expression on cultured FLSs was analyzed by ELISA. ChemR23 expression on FLSs was determined by immunocytochemistry and Western blot analysis. Cytokine production from FLSs was measured by ELISA. FLS cell motility was evaluated by utilizing a scrape motility assay. We also examined the stimulating effect of chemerin on the phosphorylation of mitogen-activated protein kinase (MAPK), p44/42 mitogen-activated protein kinase (ERK1/2), p38MAPK, c-Jun N-terminal kinase (JNK)1/2 and Akt, as well as on the degradation of regulator of NF-κB (IκBα) in FLSs, by Western blot analysis.

Results

Chemerin was expressed on endothelial cells and synovial lining and sublining cells. ChemR23 was expressed on macrophages, immature DCs and FLSs and a few mature DCs in the RA synovium. Chemerin and ChemR23 were highly expressed in the RA synovium compared with osteoarthritis. Chemerin and ChemR23 were expressed on unstimulated FLSs. TNF-α and IFN-γ upregulated chemerin production. Chemerin enhanced the production of IL-6, chemokine (C-C motif) ligand 2 and matrix metalloproteinase 3 by FLSs, as well as increasing FLS motility. The stimulatory effects of chemerin on FLSs were mediated by activation of ERK1/2, p38MAPK and Akt, but not by JNK1/2. Degradation of IκB in FLSs was not promoted by chemerin stimulation. Inhibition of the ERK1/2, p38MAPK and Akt signaling pathways significantly suppressed chemerin-induced IL-6 production. Moreover, blockade of the p38MAPK and Akt pathways, but not the ERK1/2 pathway, inhibited chemerin-enhanced cell motility.

Conclusions

The interaction of chemerin and ChemR23 may play an important role in the pathogenesis of RA through the activation of FLSs.     

Gene expression induced by interleukin-17 in fibroblast-like synoviocytes of patients with rheumatoid arthritis: upregulation of hyaluronan-binding protein TSG-6

Interleukin-17 (IL-17) has been characterized as a proinflammatory cytokine produced by CD4+ CD45RO+ memory T cells. Overproduction of IL-17 was detected in the synovium of patients with rheumatoid arthritis (RA) compared with patients with osteoarthritis. This study examines differentially expressed genes after the stimulation of fibroblast-like synoviocytes of RA patients by IL-17. Among these genes we identified the following: tumor necrosis factor-stimulated gene-6 (TSG-6), IL-6, IL-8, GRO-beta, and bone morphogenetic protein-6 with an expression 3.6-10.6-fold that in the unstimulated control. IL-17 augmented the expression of TSG-6, a hyaluronan-binding protein, in a time- and dose-dependent manner. IL-17 showed additive effects with IL-1beta and tumour necrosis factor-alpha on the expression of TSG-6, IL-6 and IL-8. The mitogen-activated protein kinase p38 seems to be necessary for the regulation of TSG-6 expression by IL-17, as shown by inhibition with SB203580. Our results support the hypothesis that IL-17 is important in the pathogenesis of RA, contributing to an unbalanced production of cytokines as well as participating in connective tissue remodeling.     

Innate immunity triggers IL-32 expression by fibroblast-like synoviocytes in rheumatoid arthritis

Introduction  

Interleukin-32 (IL-32) is a recently described cytokine that is a strong inducer of pro-inflammatory cytokines such as tumor necrosis factor (TNF)-α, IL-1β, IL-6, and IL-8. The expression of this cytokine is highly increased in the rheumatoid synovium and correlated with the severity of joint inflammation. Little is known regarding the innate immune-related regulation of IL-32 by fibroblast-like synoviocytes (FLSs). We therefore investigated the effect of innate immune stimulation by ligands of Toll-like receptor (TLR)2, TLR3, and TLR4, and cytokines such as TNF-α and interferon (IFN)-γ, on IL-32 expression by FLSs.     

Geldanamycin induces apoptosis and inhibits inflammation in fibroblast-like synoviocytes isolated from rheumatoid arthritis patients

Rheumatoid arthritis (RA) is an autoimmune disease of the joints characterized by synovial hyperplasia and chronic inflammation. Fibroblasts-like synoviocytes (FLS), major cells in the synovium, together with infiltrated leukocytes, contribute greatly to RA progression. In our study, we hypothesized that geldanamycin (GA), a cancer drug might be able to inhibit RA FLS growth. To test the idea, RA FLS were isolated and cultured for cancer drug test. The results showed that GA can specifically inhibit the growth of RA FLS compared with normal FLS. Essentially, GA was found to promote reactive oxygen species production in RA FLS and induce programmed cell death. The annexinV/propidium iodide and terminal deoxynucleotidyl transferase dUTP nick-end labeling staining confirmed that GA can directly induce apoptosis and subsequently inhibit the growth of RA FLS, which was also confirmed by Western blot assay. In addition, our data demonstrated that inflammation was inhibited by suppressed nuclear factor κB signaling pathway. The therapeutic effect of GA was explored in collagen-induced arthritis mice. In short, GA was a promising drug for the treatment of RA by specifically inhibiting the proliferation and inflammation of RA FLS.     

Macrophage migration inhibitory factor: a mediator of matrix metalloproteinase-2 production in rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic inflammatory disease characterized by destruction of bone and cartilage, which is mediated, in part, by synovial fibroblasts. Matrix metalloproteinases (MMPs) are a large family of proteolytic enzymes responsible for matrix degradation. Macrophage migration inhibitory factor (MIF) is a cytokine that induces the production of a large number of proinflammatory molecules and has an important role in the pathogenesis of RA by promoting inflammation and angiogenesis.     

The GTPase Rac regulates the proliferation and invasion of fibroblast-like synoviocytes from rheumatoid arthritis patients

Fibroblast-like synoviocytes (FLS) isolated from joints of rheumatoid arthritis (RA) patients display proliferative and invasive properties reminiscent of those of malignant tumor cells. Rac small GTPases play an important role in tumor cell proliferation and invasion. We therefore investigated the potential role of Rac proteins in the proliferative and invasive behavior of RA-FLS. We showed that inhibiting Rac activity with the Rac-specific small molecule inhibitor NSC23766 causes a strong inhibition of RA-FLS proliferation, without affecting cell survival. Rac inhibition also results in a strong reduction in RA-FLS invasion through reconstituted extracellular matrix and a less marked inhibition of two-dimensional migration as measured by monolayer wound healing. We also showed that small interfering RNA-mediated depletion of Rac1 inhibits RA-FLS proliferation and invasion to a similar extent as NSC23766. These results demonstrate for the first time that Rac proteins play an important role in the aggressive behavior of FLS isolated from RA patients. In addition, we observed that inhibiting Rac proteins prevents JNK activation and that the JNK inhibitor SP600125 strongly inhibits RA-FLS invasion, suggesting that Rac-mediated JNK activation contributes to the role of Rac proteins in the invasive behavior of RA-FLS. In conclusion, Rac-controlled signaling pathways may present a new source of drug targets for therapeutic intervention in RA.     

TL1A mediates fibroblast-like synoviocytes migration and Indian Hedgehog signaling pathway via TNFR2 in patients with rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic autoimmune disease characterized by joints inflammation. One of the aggressive characteristics of RA fibroblast-like synoviocytes (FLS) is the tendency for migration in the local environment, which plays a central role in the RA pathogenesis. Tumor Necrosis Factor (TNF)-like cytokine 1A (TL1A) is a member of TNF superfamily, which has a role in autoimmunity and influences the RA-FLS behavior through TNF receptor 2 (TNFR2).We investigated the effect of TNF-like cytokine 1A (TL1A) on RA-FLS migration using patients’ samples. Specifically, we examined the hedgehog signaling pathway which is a key regulator in chondrocyte growth and differentiation. We found that TL1A increased significantly the hedgehog homologue Indian hedgehog (IHH) and its receptor Patched 1, 2 (PTCH 1, 2) in RA-FLS. In addition, TL1A-stimulated RA-FLS promoted significantly IHH protein expression. However, both mRNA and protein levels decreased substantially after blocking TL1A with TNFR2 antagonist. The migratory property of RA-FLS was enhanced after stimulation of RA-FLS with TL1A, but was compromised following TL1A blockage. In conclusion, our study has revealed that TL1A modulated RA-FLS migration and Indian hedgehog signaling pathway using TNFR2.     

Betulinic acid inhibits cell proliferation,migration, and inflammatory response in rheumatoid arthritis fibroblast-like synoviocytes

Betulinic acid (BA), a pentacyclic triterpene derived from the bark of the white birch tree, has been reported to have a variety of pharmacological effects, including antioxidant, anti-inflammatory, antitumor, immunomodulatory, and antiarthritis properties. However, the role of BA in rheumatoid arthritis (RA) remains unclear. Thus, the objective of this study was to examine the effects of BA on RA fibroblast-like synoviocytes (RA-FLS) proliferation, migration, and inflammatory response, and further explore the potential underlying mechanisms. Our results showed that BA inhibited the proliferation, migration, and invasion of RA-FLSs. BA also attenuated tumor necrosis factor-α (TNF-α), enhanced matrix metalloproteinases (MMPs) expression, and inflammatory cytokines production in RA-FLS. Furthermore, BA prevented the activation of Akt/NF-κB pathway in RA-FLS exposed to TNF-α. In conclusion, these findings indicated that BA inhibits cell proliferation, migration, and inflammatory response in RA-FLS; and the Akt/NF-κB signaling pathway was involved in the protective effect of BA on RA-FLS. Thus, BA might be a potential therapeutic agent for the treatment of RA.     

Chemokines regulate IL-6 and IL-8 production by fibroblast-like synoviocytes from patients with rheumatoid arthritis.

Rheumatoid arthritis (RA) is characterized by proliferation of synoviocytes that produce inflammatory cytokines and chemokines. The expressed chemokines are thought to be involved in the migration of inflammatory cells into the synovium. In this study we show that CCL2/monocyte chemotactic protein-1, CCL5/RANTES, and CXCL12/stromal cell-derived factor-1 enhanced IL-6 and IL-8 production by fibroblast-like synoviocytes (FLS) from patients with RA, and their corresponding receptors, CCR2, CCR5, and CXCR4, respectively, were expressed by RA FLS. The chemokines stimulated RA FLS more effectively than skin fibroblasts. Culture with CCL2 enhanced phosphorylation of extracellular signal-related kinase 1 (ERK1) and ERK2, but not phosphorylation of p38 or Src. Moreover, activation of ERK1/2 was inhibited by pertussis toxin, a G(i)-coupled protein inhibitor, and RS-504393, CCR2 antagonist, suggesting that ERK1/2 was activated by CCL2 via CCR2 and G(i)-coupled protein. On the other hand, CCL2, CCL5, and CXCL12 were expressed on RA FLS, and their production was regulated by TNF-alpha, IL-1beta, and TGF-beta1. Our results indicate that the chemokines not only play a role in inflammatory cell migration, but are also involved in the activation of FLS in RA synovium, possibly in an autocrine or paracrine manner.     

Apigenin enhances the cytotoxic effects of tumor necrosis factor-related apoptosis-inducing ligand in human rheumatoid arthritis fibroblast-like synoviocytes

Activated rheumatoid arthritis (RA) fibroblast-like synoviocytes (RAFLSs) play a central role in both initiating and driving RA. Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) has been documented to induce apoptosis only in a small proportion of RAFLSs, which is followed by an induction of proliferation in surviving cells. Apigenin, a chemopreventive bioflavonoid, exhibits proapoptotic activity in many types of cells. In the present study, we sought to determine whether apigenin could enhance the cytotoxic effect of TRAIL on activated RAFLSs. Human RAFLSs isolated from patients with RA were treated with TRAIL (1 nM), apigenin (20 μM), or their combination, and subjected to apoptosis analysis after a 24-h incubation and proliferation analysis after a 72-h incubation. Apoptosis assay revealed that TRAIL or apigenin alone induced a marked apoptosis in RAFLS and their combination yielded a synergistic increase in RAFLS apoptosis. Immunoblotting analysis of apoptosis regulators demonstrated that combined treatment with apigenin increased caspase-3 expression and activity and decreased the Bcl-2/Bax ratio relative to treatment with TRAIL alone. The presence of apigenin significantly restrained TRAIL-induced RAFLS proliferation, coupled with restoration of the expression of two cell-cycle inhibitors p21 and p27. Moreover, the combination with apigenin blunted TRAIL-induced activation of the phosphatidylinositol 3-kinase (PI3-K)/Akt pathway. Our data collectively demonstrate that apigenin sensitizes RAFLS to TRAIL-induced apoptosis and counteracts TRAIL-dependent RAFLS proliferation, which is likely mediated through inactivation of PI3-K/Akt signaling pathway.     

Upregulated expression of CCR3 in rheumatoid arthritis and CCR3-dependent activation of fibroblast-like synoviocytes

It is recognized that CC chemokine receptor 3 (CCR3) is associated with numerous inflammatory conditions and fibroblast-like synoviocyte (FLS) invasiveness correlates with articular damage in rheumatoid arthritis (RA). However, little is known of the expression and action of CCR3 on FLS in RA. In the present study, we investigated the expression of CCR3 on dispersed synovial tissue and peripheral blood cells in RA and influence of eotaxin-1 on FLS functions by using flow cytometry analysis, FLS challenge, and real-time PCR techniques. The results showed that approximately 7.0 % dispersed synovial cells are CCR3+ cells. Among those CCR3+ cells, 38.1, 23.8, and 20.6 % cells are CD90+CD14?CD3? (representing FLS), CD14+, and CD8+ cells, respectively, indicating that FLS is one of the major populations of CCR3+ cells in the synovial tissue of RA. In peripheral blood, CD14+ CCR3+ cells are elevated, but CD8+CCR3+ cells are reduced in RA. It was found that eotaxin-1 induced upregulated expression of CCR3 and matrix metalloproteinase (MMP)-9 messenger RNAs (mRNAs) in FLS. Since an antagonist of CCR3 suppressed the action of eotaxin-1, the event appeared CCR3 dependent. Moreover, we observed that interleukin (IL)-1β induced markedly enhanced eotaxin-1 release from FLS, but TNF-α reduced eotaxin-1 release at 12 and 24 h following incubation. In conclusion, enhanced expression of CCR3 on synovial cells and increased levels of eotaxin-1 in plasma and synovial fluid (SF) of RA indicate that CCR3-mediated mechanisms may play an important role in RA. Blockage of eotaxin-1 provoked CCR3 and MMP-9 expression in FLS by antagonist of CCR3, implicating that anti-CCR3 agents may have therapeutic use for RA.     

Macrophage migration inhibitory factor in Nodding syndrome

Nodding syndrome (NS) is a catastrophic and enigmatic childhood epilepsy, accompanied by multiple neurological impairments and neuroinflammation. Of all the infectious, environmental and psychological factors associated with NS, the major culprit is Onchocerca Volvulus (Ov)–a parasitic worm transmitted to human by blackflies. NS seems to be an ’Autoimmune Epilepsy’ in light of the recent findings of deleterious autoimmune antibodies to Glutamate receptors and to Leiomodin-I in NS patients. Moreover, we recently found immunogenetic fingerprints in HLA peptide-binding grooves associate with protection or susceptibility to NS. Macrophage migration inhibitory factor (MIF) is an immune-regulatory cytokine playing a central role in modulating innate and adaptive immunity. MIF is also involved in various pathologies: infectious, autoimmune and neurodegenerative diseases, epilepsy and others. Herein, two functional polymorphisms in the MIF gene, a −794 CATT_5–8 microsatellite repeat and a −173 G/C single-nucleotide polymorphism, were assessed in 49 NS patients and 51 healthy controls from South Sudan. We also measured MIF plasma levels in established NS patients and healthy controls. We discovered that the frequency of the high-expression MIF -173C containing genotype was significantly lower in NS patients compared to healthy controls. Interestingly however, MIF plasma levels were significantly elevated in NS patients than in healthy controls. We further demonstrated that the HLA protective and susceptibility associations are dominant over the MIF association with NS. Our findings suggest that MIF might have a dual role in NS. Genetically controlled high-expression MIF genotype is associated with disease protection. However, elevated MIF in the plasma may contribute to the detrimental autoimmunity, neuroinflammation and epilepsy.     

Macrophage migration inhibitory factor: Isolation from bovine brain

The purification of macrophage migration inhibitory factor (MIF) from bovine brain cytosol and its partial characterization are reported. A rapid and relatively simple method for MIF isolation was developed based mainly on size-exclusion chromatography on Toyopearl TSK polymer having a tendency to adsorb MIF as compared to elution of other proteins with similar molecular weights. The method gives a high yield of MIF (0.1 mg homogenous protein per g wet tissue). The retardation is conveniently utilized to achieve good separations of MIF from other proteins of similar molecular weights. The isolated protein was identified as MIF by SDS-electrophoresis, immunoblotting, sequencing of the N-terminal amino acid residues, and also by determination of keto-enol tautomerase activity that is characteristic of MIF with p-hydroxyphenylpyruvic acid as a substrate.