Pathogenesis of rheumatoid arthritis: the role of synoviocytes

Role of high-temperature requirement serine protease A 2 in rheumatoid inflammation

BACKGROUND

High-temperature requirement serine protease A 2 (HtrA2) is known to be involved in growth, unfolded protein response to stress, apoptosis, and autophagy. However, whether HtrA2 controls inflammation and immune response remains elusive.

METHODS

Expression of HtrA2 in the synovial tissue of patients was examined using immunohistochemistry and immunofluorescence staining. Enzyme-linked immunosorbent assay was used to determine the concentrations of HtrA2, interleukin-6 (IL-6), interleukin-8 (IL-8), chemokine (C-C motif) ligand 2 (CCL2), and tumor necrosis factor α (TNFα). Synoviocyte survival was assessed by MTT assay. For the downregulation of HtrA2 transcripts, cells were transfected with HtrA2 siRNA.

RESULTS

We found that the concentration of HtrA2 was elevated in rheumatoid arthritis (RA) synovial fluid (SF) than in osteoarthritis (OA) SF, and its concentrations were correlated with the number of immune cells in the RA SF. Interestingly, HtrA2 levels in the SF of RA patients were elevated in proportion to synovitis severity and correlated with the expression of proinflammation cytokines and chemokines, such as IL-6, IL-8, and CCL2. In addition, HtrA2 was highly expressed in RA synovium and primary synoviocytes. RA synoviocytes released HtrA2 when stimulated with ER stress inducers. Knockdown of HtrA2 inhibited the IL1β-, TNFα-, and LPS-induced release of proinflammatory cytokines and chemokines by RA synoviocytes.

CONCLUSION

HtrA2 is a novel inflammatory mediator and a potential target for the development of an anti-inflammation therapy for RA.

DHA Induces Cell Death through the Production of ROS and the Upregulation of CHOP in Fibroblast-like Synovial Cells from Human Rheumatoid Arthritis Patients

Rheumatoid arthritis (RA) is an inflammatory disease marked by a massive proliferation of synovial cells in the joints. In this study, we investigated the pro-apoptotic effects of docosahexaenoic acid (DHA) in human fibroblast-like synovial cells from RA patients (RA-FLS). An in vitro study using MH7A cells showed that DHA treatment induced caspase-8-dependent apoptosis in a dose-dependent manner and reduced the TNF-α-mediated induction of MMP-9 and IL-1β. DHA also induced the phosphorylation of eIF2α, the expression of the ER stress markers ATF4 and C/EBP homologous protein (CHOP), and death receptor 5 (DR5). The knockdown of CHOP or DR5 increased cell viability and reduced apoptosis in DHA-treated cells. Furthermore, the knockdown of CHOP reduced DHA-mediated DR5 expression, while the overexpression of CHOP increased DR5 expression. We also found that DHA treatment induced the accumulation of reactive oxygen species (ROS), and pretreatment with the anti-oxidant Tiron effectively abrogated not only the expression of CHOP and DR5, but also DHA-induced apoptosis. Under this condition, cell viability was increased, while PARP-1 cleavage and caspase-8 activation were reduced. All the findings were reproduced in human primary synovial cells obtained from RA patients. These results suggest that the DHA-mediated induction of ROS and CHOP induced apoptosis through the upregulation of DR5 in RA-FLSs, and that CHOP could be used as a therapy for RA.

Bioactive fractions and compound of Ardisia crispa roots exhibit anti-arthritic properties mediated via angiogenesis inhibition in vitro

Background

Ardisia crispa (Thunb.) A.DC (Primulaceae), is a medicinal herb traditionally used by Asian people as remedies to cure inflammatory related diseases, including rheumatism. The plant roots possess various pharmacological activities including antipyretic, anti-inflammation and antitumor. Previous phytochemical studies of the plant roots have identified long chain alkyl-1,4-benzoquinones as major constituents, together with other phytochemicals. Hexane fraction of the plant roots (ACRH), was previously reported with anti-angiogenic and anti-arthritic properties, while its effect on their anti-arthritic in vitro, is yet unrevealed. Considering the significance of angiogenesis inhibition in developing new anti-arthritic agent, thus we investigated the anti-arthritic potential of Ardisia crispa roots by suppressing angiogenesis, in vitro.

Methods

Ardisia crispa roots hexane extract (ACRH) was prepared from the plant roots using absolute n-hexane. ACRH was fractionated into quinone-rich fraction (QRF) and further isolated to yield benzoquinonoid compound (BQ), respectively. In vitro experiments using VEGF-induced human umbilical vein endothelial cells (HUVECs) and IL-1β-induced human fibroblast-like synoviocytes for rheumatoid arthritis (HFLS-RA) were performed to evaluate the effects of these samples on VEGF-induced HUVECs proliferation and tube formation, and towards IL-1β-induced HFLS-RA proliferation, invasion, and apoptosis, respectively. Therapeutic concentrations (0.05, 0.5, and 5 μg/mL) tested in this study were predetermined based on the IC₅₀ values obtained from the MTT assay.

Results

ACRH, QRF, and BQ exerted concentration-independent antiproliferative effects on VEGF-induced HUVECs and IL-1β-induced HFLS-RA, with IC₅₀ values at 1.09 ± 0.18, 3.85 ± 0.26, and 1.34 ± 0.16 μg/mL in HUVECs; and 3.60 ± 1.38, 4.47 ± 0.34, and 1.09 ± 0.09 μg/mL in HFLS-RA, respectively. Anti-angiogenic properties of these samples were verified via significant inhibition on VEGF-induced HUVECs tube formation, in a concentration-independent manner. The invasiveness of IL-1β-induced HFLS-RA was also significantly inhibited in a concentration-independent manner by all samples. ACRH and BQ, but not QRF, significantly enhanced the apoptosis of IL-1β-induced HFLS-RA elicited at their highest concentration (5 μg/mL) (P < 0.05).

Conclusions

These findings highlight the bioactive fractions and compound from Ardisia crispa roots as potential anti-arthritic agents by inhibiting both HUVECs and HFLS-RA’s cellular functions in vitro, possibly mediated via their anti-angiogenic effects.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12906-021-03341-y.

Molecular Imaging of Inflammatory Disease

Inflammatory diseases include a wide variety of highly prevalent conditions with high mortality rates in severe cases ranging from cardiovascular disease, to rheumatoid arthritis, to chronic obstructive pulmonary disease, to graft vs. host disease, to a number of gastrointestinal disorders. Many diseases that are not considered inflammatory per se are associated with varying levels of inflammation. Imaging of the immune system and inflammatory response is of interest as it can give insight into disease progression and severity. Clinical imaging technologies such as computed tomography (CT) and magnetic resonance imaging (MRI) are traditionally limited to the visualization of anatomical information; then, the presence or absence of an inflammatory state must be inferred from the structural abnormalities. Improvement in available contrast agents has made it possible to obtain functional information as well as anatomical. In vivo imaging of inflammation ultimately facilitates an improved accuracy of diagnostics and monitoring of patients to allow for better patient care. Highly specific molecular imaging of inflammatory biomarkers allows for earlier diagnosis to prevent irreversible damage. Advancements in imaging instruments, targeted tracers, and contrast agents represent a rapidly growing area of preclinical research with the hopes of quick translation to the clinic.

D-Lactate Increases Cytokine Production in Bovine Fibroblast-Like Synoviocytes via MCT1 Uptake and the MAPK, PI3K/Akt, and NFκB Pathways

Acute ruminal acidosis (ARA) is caused by the excessive intake of highly fermentable carbohydrates, followed by the massive production of D-lactate and the appearance of neutrophilic aseptic polysynovitis. Bovines with ARA develop different lesions, such as ruminitis, polioencephalomalacia (calves), liver abscess and lameness. Lameness in cattle with ARA is closely associated with the presence of laminitis and polysynovitis. However, despite decades of research in bovine lameness as consequence of ruminal acidosis, the aetiology and pathogenesis remain unclear. Fibroblast-like synoviocytes (FLSs) are components of synovial tissue, and under pathological conditions, FLSs increase cytokine production, aggravating inflammatory responses. We hypothesized that D-lactate could induce cytokine production in bovine FLSs. Analysis by qRT-PCR and ELISA revealed that D-lactate, but not L-lactate, increased the expression of IL-6 and IL-8 in a monocarboxylate transporter-1-dependent manner. In addition, we observed that the inhibition of the p38, ERK1/2, PI3K/Akt, and NF-κB pathways reduced the production of IL-8 and IL-6. In conclusion, our results suggest that D-lactate induces an inflammatory response; this study contributes to the literature by revealing a potential key role of D-lactate in the polysynovitis of cattle with ARA.

Discrepancy between Jun/Fos Proto-Oncogene mRNA and Protein Expression in the Rheumatoid Arthritis Synovial Membrane

Rheumatoid arthritis (RA) is a chronic inflammatory and destructive joint disease characterized by overexpression of pro-inflammatory/pro-destructive mediators, whose regulation has been the focus of our previous studies. Since the expression of these proteins commonly depends on AP-1, the expression of the AP-1-forming subunits cJun, JunB, JunD, and cFos was assessed in synovial membrane (SM) samples of RA, osteoarthritis (OA), joint trauma (JT), and normal controls (NC) using ELISA and qRT-PCR. With respect to an observed discrepancy between mRNA and protein levels, the expression of the mRNA stability-modifying factors AU-rich element RNA-binding protein (AUF)-1, tristetraprolin (TTP), and human antigen R (HuR) was measured. JunB and JunD protein expression was significantly higher in RA-SM compared to OA and/or NC. By contrast, jun/fos mRNA expression was significantly (cjun) or numerically decreased (junB, junD, cfos) in RA and OA compared to JT and/or NC. Remarkably, TTP and HuR were also affected by discrepancies between their mRNA and protein levels, since they were significantly decreased at the mRNA level in RA versus NC, but significantly or numerically increased at the protein level when compared to JT and NC. Discrepancies between the mRNA and protein expression for Jun/Fos and TTP/HuR suggest broad alterations of post-transcriptional processes in the RA-SM. In this context, increased levels of mRNA-destabilizing TTP may contribute to the low levels of jun/fos and ttp/hur mRNA, whereas abundant mRNA-stabilizing HuR may augment translation of the remaining mRNA into protein with potential consequences for the composition of the resulting AP-1 complexes and the expression of AP-1-dependent genes in RA.

Cyanidin prevents the hyperproliferative potential of fibroblast-like synoviocytes and disease progression via targeting IL-17A cytokine signalling in rheumatoid arthritis

The hyperplastic phenotype of fibroblast-like synoviocytes (FLSs) plays an important role for synovitis, chronic inflammation and joint destruction in rheumatoid arthritis (RA). Interleukin 17A (IL-17A), a signature pro-inflammatory cytokine effectively influences the hyperplastic transformation of FLS cells and synovial pannus growth. IL-17A cytokine signalling participates in RA pathology by regulating an array of pro-inflammatory mediators and osteoclastogenesis. Cyanidin, a key flavonoid inhibits IL-17A/IL-17 receptor A (IL-17RA) interaction and alleviates progression and disease severity of psoriasis and asthma. However, the therapeutic efficacy of cyanidin on IL-17A cytokine signalling in RA remains unknown. In the present study, cyanidin inhibited IL-17A induced migratory and proliferative capacity of FLS cells derived from adjuvant-induced arthritis (AA) rats. Cyanidin treatment reduced IL-17A mediated reprogramming of AA-FLS cells to overexpress IL-17RA. In addition, significantly decreased expression of IL-17A dependent cyr61, IL-23, GM-CSF, and TLR3 were observed in AA-FLS cells in response to cyanidin. At the molecular level, cyanidin modulated IL-17/IL-17RA dependent JAK/STAT-3 signalling in AA-FLS cells. Importantly, cyanidin activated PIAS3 protein to suppress STAT-3 specific transcriptional activation in AA-FLS cells. Cyanidin treatment to AA rats attenuated clinical symptoms, synovial pannus growth, immune cell infiltration, and bone erosion. Cyanidin reduced serum level of IL-23 and GM-CSF and expression of Cyr 61 and TLR3 in the synovial tissue of AA rats. Notably, the level of p-STAT-3 protein was significantly decreased in the synovial tissue of AA rats treated with cyanidin. This study provides the first evidence that cyanidin can be used as IL-17/17RA signalling targeting therapeutic drug for the treatment of RA and this need to be investigated in RA patients.

Association of Human FOS Promoter Variants with the Occurrence of Knee-Osteoarthritis in a Case Control Association Study

Our aim was to analyse (i) the presence of single nucleotide polymorphisms (SNPs) in the JUN and FOS core promoters in patients with rheumatoid arthritis (RA), knee-osteoarthritis (OA), and normal controls (NC); (ii) their functional influence on JUN/FOS transcription levels; and (iii) their associations with the occurrence of RA or knee-OA. JUN and FOS promoter SNPs were identified in an initial screening population using the Non-Isotopic RNase Cleavage Assay (NIRCA); their functional influence was analysed using reporter gene assays. Genotyping was done in RA (n = 298), knee-OA (n = 277), and NC (n = 484) samples. For replication, significant associations were validated in a Finnish cohort (OA: n = 72, NC: n = 548). Initially, two SNPs were detected in the JUN promoter and two additional SNPs in the FOS promoter in perfect linkage disequilibrium (LD). JUN promoter SNP rs4647009 caused significant downregulation of reporter gene expression, whereas reporter gene expression was significantly upregulated in the presence of the FOS promoter SNPs. The homozygous genotype of FOS promoter SNPs showed an association with the susceptibility for knee-OA (odds ratio (OR) 2.12, 95% confidence interval (CI) 1.2–3.7, p = 0.0086). This association was successfully replicated in the Finnish Health 2000 study cohort (allelic OR 1.72, 95% CI 1.2–2.5, p = 0.006). FOS Promoter variants may represent relevant susceptibility markers for knee-OA.

Theaflavin-3, 3'-Digallate Attenuates Rheumatoid Inflammation in Mice Through the Nuclear Factor-κB and MAPK Pathways

Rheumatoid arthritis (RA) is a common autoimmune disease which impacts a large number of patients worldwide, and new drugs are required for lower the disease burden. Theaflavin-3, 3'-digallate (TFDG) is polyphenol exhibiting inhibition on inflammatory factors. This study aimed to explore the attenuation of TFDG on RA. The collagen-induced arthritis (CIA) mouse model was established and administered with TFDG. The arthritis score and incidence was recorded to assess the amelioration of TFDG on arthritis. Histopathological change of the mouse joint tissues was evaluated by haemotoxylin and eosin staining. The expression of pro-inflammatory mediators including interleukin (IL)-1β, tumor necrosis factor (TNF)-α, and IL-6 was quantified by ELISA. The activation of nuclear factor (NF)-κB and mitogen-activated protein kinase (MAPK) signaling pathways in the synovium were determined by Western blotting. In comparison with the control, administration of TFDG significantly reduced arthritis score and incidence in the CIA mouse model. TFDG significantly suppressed the expression of IL-1β, TNF-α, and IL-6, as well as the levels of MMP-1, MMP-2, and MMP-3 in the synovium. TFDG also showed remarkable inhibition on the activation of NF-κB and the phosphorylation of P38, JNK2, and ERK. This study puts up evidence that TFDG exerts protection on RA via inhibiting the activation of NF-κB- and MAPK-signaling pathways.

Astragalin Suppresses Inflammatory Responses and Bone Destruction in Mice With Collagen-Induced Arthritis and in Human Fibroblast-Like Synoviocytes

Astragalin, as a bioactive flavonoid with anti-inflammatory, antioxidant, and protective properties, provides a potential agent for rheumatoid arthritis (RA). In this study, its therapeutic efficacy and the underlying mechanisms were explored using DBA/1J mice with collagen-induced arthritis (CIA). It was demonstrated that astragalin could significantly attenuate inflammation of CIA mice. The effects were associated with decreased severity of arthritis (based on the arthritis index), joint swelling and reduced bone erosion and destruction. Furthermore, astragalin treatment suppressed the production of pro-inflammatory cytokines (TNF-α, IL-1β, IL-6, and IL-8), and inhibited the expression of matrix metalloproteinases (MMP-1, MMP-3, and MMP-13) in chondrocytes and synovial cells of CIA mice. Fibroblast-like synoviocytes derived from RA patients (MH7A cells) were applied to verify these effects. In vitro, astragalin inhibited the expression of matrix metalloproteinases (MMP-1, MMP-3, and MMP-13) dose-dependently in TNF-α-induced MH7A cells, with no apparent cytotoxicity. Furthermore, astragalin suppressed the phosphorylation of p38, JNK, and the activation of c-Jun/AP-1 in TNF-α-induced MH7A cells. In conclusion, it has proven that astragalin could attenuate synovial inflammation and joint destruction in RA at least partially by restraining the phosphorylation of MAPKs and the activating of c-Jun/AP-1. Therefore, astragalin can be a potential therapeutic agent for RA.

Applications and potential mechanisms of herbal medicines for rheumatoid arthritis treatment: a systematic review

In this review, we systematically discuss the role of traditional Chinese medicine (TCM) in rheumatoid arthritis (RA) disease treatment. TCM classifies the subtypes of RA through its own theoretical method, which is beneficial for more accurate diagnosis and treatment with Chinese herbal medicines (CHMs) that are more suitable for different syndromes. TCM mainly uses a flexible combination of CHMs to play an important role in RA treatment. The main components of these extracts can be subdivided into alkaloids, flavonoids, triterpenes, saponins and other compounds. Using a platform of transgenic and induced arthritis models, we explore the potential mechanisms of TCM against RA with the help of omics analysis techniques and methods. These mechanisms are mainly CHM and its extracts can inhibit RA patients and experimental animal models, including synovitis, vascular proliferation and bone injury; this involves many biological signal exchange targets and pathways. In conclusion, the role of TCM in RA treatment mainly involves reducing the expression and secretion of pro-inflammatory factors, thus decreasing the degree of abnormal immune response.

In this review, we systematically discuss the role of traditional Chinese medicine (TCM) in rheumatoid arthritis (RA) disease treatment.

Polyphenolic extract from extra virgin olive oil inhibits the inflammatory response in IL-1β-activated synovial fibroblasts

The polyphenolic extract (PE) from extra virgin olive oil (EVOO) has been shown to possess important anti-inflammatory and joint protective properties in murine models of rheumatoid arthritis (RA). This study was designed to evaluate the effects of PE on IL-1β-activated human synovial fibroblasts SW982 cell line. PE from EVOO treatment inhibited IL-1β-induced matrix metalloproteases (P&lt;0·001), TNF-α and IL-6 production (P&lt;0·001). Similarly, IL-1β-induced cyclo-oxygenase-2 and microsomal PGE synthase-1 up-regulations were down-regulated by PE (P&lt;0·001). Moreover, IL-1β-induced mitogen-activated protein kinase (MAPK) phosphorylation and NF-κB activation were ameliorated by PE (P&lt;0·001). These results suggest that PE from EVOO reduces the production of proinflammatory mediators in human synovial fibroblasts; particularly, these protective effects could be related to the inhibition of MAPK and NF-κB signalling pathways. Taken together, PE from EVOO probably could provide an attractive complement in management of diseases associated with over-activation of synovial fibroblasts, such as RA.

Detection and characterization of bacterial nucleic acids in culture-negative synovial tissue and fluid samples from rheumatoid arthritis or osteoarthritis patients

Human intestinal microbes can mediate development of arthritis – Studies indicate that certain bacterial nucleic acids may exist in synovial fluid (SF) and could be involved in arthritis, although the underlying mechanism remains unclear. To characterize potential SF bacterial nucleic acids, we used 16S rRNA gene amplicon sequencing to assess bacterial nucleic acid communities in 15 synovial tissue (ST) and 110 SF samples from 125 patients with rheumatoid arthritis (RA) and 16 ST and 42 SF samples from 58 patients with osteoarthritis (OA). Our results showed an abundant diversity of bacterial nucleic acids in these clinical samples, including presence of Porphyromonas and Bacteroides in all 183 samples. Agrobacterium, Comamonas, Kocuria, Meiothermus, and Rhodoplanes were more abundant in synovial tissues of rheumatoid arthritis (STRA). Atopobium, Phascolarctobacterium, Rhodotorula mucilaginosa, Bacteroides uniformis, Rothia, Megasphaera, Turicibacter, Leptotrichia, Haemophilus parainfluenzae, Bacteroides fragilis, Porphyromonas, and Streptococcus were more abundant in synovial tissues of osteoarthritis (STOA). Veillonella dispar, Haemophilus parainfluenzae, Prevotella copri and Treponema amylovorum were more abundant in synovial fluid of rheumatoid arthritis (SFRA), while Bacteroides caccae was more abundant in the synovial fluid of osteoarthritis (SFOA). Overall, this study confirms existence of bacterial nucleic acids in SF and ST samples of RA and OA lesions and reveals potential correlations with degree of disease.

Osthole improves collagen-induced arthritis in a rat model through inhibiting inflammation and cellular stress

Background

Osthole is a natural product that has multiple bioactive functions and has been reported to exert potent immunosuppressive effects. However, the therapeutic effect of osthole on arthritis has not been explored. In the present study, a collagen-induced arthritis rat model, IL-1β-stimulated SW982 cells, and RA-like fibroblast-like synoviocytes (FLS) were employed to investigate the effect and possible mechanism of osthole on arthritis in vivo and in vitro.

Results

20 and 40 mg/kg osthole significantly alleviated collagen-induced arthritic symptoms based on histopathology and clinical arthritis scores, and improved erosion using HE staining. 20 and 40 mg/kg osthole decreased the level of IL-1β, TNF-α and IL-6 in rats and ameliorated oxidative stress in serum evaluated using ELISA kits. In addition, treatment with 50 and 100 μM osthole for 48 h inhibited 10 ng/ml IL-1β-stimulated proliferation and migration of SW982, and significantly inhibited the expression of matrix metalloproteinases, such as MMP-1, MMP-3 and MMP-13, as detected by western blot. 50 and 100 μM osthole also blocked the generation of IL-6 and TNF-α in IL-1β-stimulated SW982 cells. The NF-κB and MAPK pathways were also inhibited by osthole in IL-1β-treated SW982 cells.

Conclusion

These results collectively demonstrated that osthole improves collagen-induced arthritis in a rat model and IL-1β-treated SW982 cells through inhibiting inflammation and cellular stress in vivo and in vitro, and osthole might be a promising therapeutic agent for RA.

Effect of Qianghuo Erhuang Decoction on T Regulatory and T Helper 17 Cells in Treatment of Adjuvant-induced Arthritis in Rats

QianghuoErhuang Decoction (QED) is an effective recipe in treating rheumatoid arthritis. The present study aimed to explore the effects of QED on Treg and Th17 in adjuvant arthritis (AA) model. The study included 6 group rats: normal control group, AA group, AA + methotrexate (MTX) group, AA + high, moderate, and low dose QED groups. The arthritis score was significantly decreased in the MTX and high-dose QED groups compared with the AA group on days 24 and 28 (P < 0.01), respectively. The synovial tissue inflammation was attenuated by histological observation, and the proliferation of splenocytes was significantly inhibited in MTX and high-dose QED groups (P < 0.01). High-dose QED can up-regulated the percentage of Treg cells (P < 0.01) and down-regulated the percentage of Th17 cells (P < 0.05). Notably, the serum levels of IL-6, IL-17 and TNF-α were significantly decreased, while TGF-β levels were apparently elevated compared with AA group (P < 0.05, P < 0.01). Interestingly, moderate and low-dose QED had no such similar effects. In summary, high-dose QED had a therapeutic effect against adjuvant arthritis and regulated the related cytokine levels in serum. The underlying mechanism might be mediated via restoration of the imbalance in CD4⁺ T lymphocyte subsets, Treg/Th17.

Oleuropein down-regulated IL-1β-induced inflammation and oxidative stress in human synovial fibroblast cell line SW982

Rheumatoid arthritis (RA) is a chronic and systemic inflammatory autoimmune disease mainly characterized by aggressive hyperproliferation of synovial fibroblasts (SFs). It is accompained by a massive infiltration of inflammatory immune cells inducing progressive matrix degradation, destruction of cartilage and bone erosion through the production of inflammatory mediators. Oleuropein is the most prevalent phenolic component in olive leaves, seed, pulp and peel of unripe olives and is responsible for the characteristic bitter taste of unprocessed olives. This secoiridoid possesses well-documented pharmacological properties, including antioxidant and anti-inflammatory properties, and is available as a food supplement in Mediterranean countries. However, to date, anti-arthritic effects of oleuropein on SFs have not been yet elucidated. Thus, the aim of the present study was to investigate the potential effects of oleuropein, on IL-1β-induced production of inflammatory mediators and oxidative stress in the human synovial sarcoma cell line (SW982). In order to gain a better insight into mechanisms of action, signaling pathways were also explored. Cell viability was determined using the sulforhodamine B (SRB) assay. The expression of inflammatory cytokines IL-6, TNF-α, MMP-1 and MMP-3 was evaluated by ELISA. Moreover, changes in the protein expression of cyclooxygenase (COX)-2, microsomal prostaglandin E synthase-1 (mPGES-1) as well as mitogen-activated protein kinase (MAPKs), nuclear factor kappa B (NF-κB), and nuclear factor-erythroid 2-related and heme oxygenase-1 (HO-1) signalling pathways were analysed by western blot. Oleuropein exerted anti-inflammatory and anti-oxidant effects via down-regulation of MAPK and NF-κB signaling pathways and induction of Nrf2-linked HO-1 controlling the production of inflammatory mediators decreasing IL-6 and TNF-α cytokines, MMP-1 and MMP-3 levels and mPGES-1 and COX-2 overexpression. Thus, oleuropein might provide a basis for developing a new dietary strategy for the prevention and management of RA.

Opposing Regulation of Interleukin-8 and NF-kB Responses by Lipoxin A4 and Serum Amyloid a via the Common Lipoxin a Receptor

Lipoxin A4 (LXA4) is a potent eicosanoid that inhibits IL-1β-induced activation of human fibroblast-like synoviocytes (FLS) via the LXA4 receptor (ALXR). Serum amyloid A (SAA) is an acute phase reactant with cytokine-like properties. SAA has been shown to bind the same seven transmembrane G protein-coupled receptor ligated by LXA4. Here we compared the inflammatory responses of lipid (LXA4) and peptide (SAA) ligands in human FLS via the shared ALX and characterized their downstream signaling. LXA4 induced stimulation of tissue inhibitors of metalloproteinase-2, whereas SAA induced interleukin-8 and matrix metalloproteinase-3 production. SAA up-regulated NF-kB and AP-1 DNA binding activity, while LXA4 markedly inhibited these responses after IL-1β stimulation. A human IL-8 promoter luciferase construct was transfected into CHO cells stably expressing ALXR in order to determine the role of NF-kB and/or AP-1 in the regulation of IL-8 gene expression. The NF-kB pathway proved to be the preeminent for the biological responses elicited by both ligands. These findings suggest that two endogenous molecules, targeting a common receptor, could participate in the pathogenesis of inflammatory arthritis by differentially regulating inflammatory responses in tissues expressing the ALXR.

Anti-rheumatic effects of Aconitum leucostomum Worosch. on human fibroblast-like synoviocyte rheumatoid arthritis cells

The aim of the present study was to investigate the effects of Aconitum leucostomum Worosch. crude drug, processed products and monomer components on human fibroblast-like synoviocyte rheumatoid arthritis (HFLS-RA) cells, and its associated mechanisms. Following drug treatment, cell proliferation was assessed using a Cell Counting Kit-8 assay. Cellular apoptosis and cell cycle were evaluated using flow cytometry. Levels of hypoxia-inducible factor 1α (HIF-1α), vascular endothelial growth factor (VEGF) and toll-like receptor 4 (TLR4) mRNA and protein were evaluated using reverse transcription-quantitative polymerase chain reaction (RT-qPCR) and western blot analysis, respectively. Levels of pro-inflammatory cytokines were evaluated using ELISA. Analysis of cell proliferation indicated that crude drug and processed products markedly inhibited the cell proliferation. Compared with the control group, the apoptosis rates were significantly elevated in all treatment groups (all P<0.05). Furthermore, the proportion of cells in G0/G1 phase was significantly decreased in all treatment groups compared with the control group (all P<0.05). RT-qPCR and western blotting indicated that, compared with the control group, mRNA and protein expression levels of HIF-1α, and TLR4 were significantly downregulated in all treatment groups (P<0.05). The mRNA and protein expression levels of VEGF in all treatment groups were decreased compared with those in the control group, but the difference was not significant. Results from ELISA demonstrated that the levels of interleukin (IL)-6, IL-1β and tumor necrosis factor-α in the cell culture supernatant were all significantly decreased following drug treatment in HFLS-RA cells (all P<0.05). Therefore, A. leucostomum Worosch. crude drug, processed products and monomer components may exert anti-rheumatic effects on HFLS-RA cells, inhibiting cell proliferation and enhancing cellular apoptosis. These effects may be attributable to the downregulated expression of HIF-1α and TLR4, as well as decreased levels of pro-inflammatory cytokines.

Synovial cellular and molecular markers in rheumatoid arthritis

The profound alterations in the structure, cellular composition, and function of synovial tissue in rheumatoid arthritis (RA) are the basis for the persistent inflammation and cumulative joint destruction that are hallmarks of this disease. In RA, the synovium develops characteristics of a tertiary lymphoid organ, with extensive infiltration of lymphocytes and myeloid cells. Concurrently, the fibroblast-like synoviocytes undergo massive hyperplasia and acquire a tissue-invasive phenotype. In this review, we summarize key components of these processes, focusing on recently-described roles of selected molecular markers of these cellular components of RA synovitis.

Apoptotic Effect of Geniposide on Fibroblast-Like Synoviocytes in Rats with Adjuvant-Induced Arthritis via Inhibiting ERK Signal Pathway In Vitro

Stimulating fibroblast-like synoviocyte (FLS) apoptosis in rheumatoid arthritis (RA) is a promising strategy for clinical treatment. Previous studies have confirmed that geniposide shows a certain anti-arthritic effect in vivo. However, whether geniposide can induce RA FLS apoptosis and the underlying mechanisms has not been elucidated. Herein, adjuvant-induced arthritis (AIA) in rat was induced and FLS was isolated from synovial tissues by tissue explant cultivation method. MTT assay, Hoechst staining, and flow cytometric apoptosis assay were applied to evaluate apoptotic effect of geniposide on AIA FLS. Bcl-2, Bax, and caspase 3 messenger RNA (mRNA) levels, and extracellular-signal-regulated kinases (ERKs) and phosphorylated ERK protein levels were examined by real-time PCR and western blot, respectively. We found that geniposide dose-dependently inhibited AIA FLS proliferation in vitro. AIA FLS treated with geniposide displayed typical apoptotic morphological characteristics including nuclear shrinkage and chromatin condensation. Flow cytometric apoptosis assay indicated that geniposide significantly increased the apoptosis rate of AIA FLS. Additionally, geniposide treatment on AIA FLS decreased Bcl-2 mRNA level and increased Bax and caspase 3 mRNA levels, accompanied by reduced protein levels of phosphorylated-ERK1/2, without affecting total ERK1/2. In conclusion, geniposide effectively induces AIA FLS apoptosis through regulating the apoptosis-related gene expressions and inhibiting ERK signal pathway.

KPNA2 Contributes to the Inflammatory Processes in Synovial Tissue of Patients with Rheumatoid Arthritis and SW982 Cells

Karyopherin-α2 (KPNA2) functions as an adaptor that transports several proteins to the nucleus. We investigated the function and possible mechanisms of KPNA2 involved in rheumatoid arthritis (RA). Western blotting and immunohistochemistry showed the protein expression of KPNA2 increased in synovial tissue of RA patients compared with the healthy controls. Double immunofluorescent staining indicated that KPNA2 co-localized with T cells, macrophage-like synoviocytes, fibroblast-like synoviocytes, and neutrophils in synovial tissue of RA patients. Moreover, the expression of KPNA2 in SW982 cells was increased in a time-dependent manner in response to TNFα stimulation. Both Western blotting and immunofluorescent staining assay revealed the co-localization of KPNA2 and P65 and their translocation from cytoplasma in TNFα-treated SW982 cells. Furthermore, knocking down the expression of KPNA2 by siRNA inhibited TNFα-induced expression of IL-6, MMP-1, and MMP-13 and, more importantly, decreased the P65 phosphorylation in SW982 cells. We therefore suggested that KPNA2 may play a key role in the inflammation process of RA via NF-κB P65 signal transduction pathway.

Interleukin-22 Secreted by NKp44+ Natural Killer Cells Promotes Proliferation of Fibroblast-Like Synoviocytes in Rheumatoid Arthritis

Although CD3-CD56+NKp44+ natural killer (NKp44+NK) cells have been linked to autoimmune diseases including inflammatory bowel disease, ankylosing spondylitis, and primary Sjogren syndrome, the expansion and role of those cells in patients with rheumatoid arthritis (RA) remain less defined. Here, we investigate the proportion and pathogenesis of NKp44+NK cells in patients with RA. The results show NKp44+NK cells significantly expanded in RA peripheral blood and synovial fluid, which were correlated positively with RA disease activity. They also highly expressed in RA synovial tissues and secreted a high concentration of interleukin-22 (IL-22) in vitro. Further, NKp44+NK cells culture supernatant promoted the proliferation of fibroblast-like synoviocytes (FLS) which was blocked by IL-22 antagonist and AG490. Treated with recombination human IL-22, the proliferation and phosphorylation-STAT3 on RA-FLS increased in a dose-dependent manner and time-dependent manner; the progress of which could be blocked by AG490. The present study clarifies the expansion of NKp44+NK cells in the peripheral blood and synovial fluid of patients with RA, especially in the synovial tissues of RA for the first time. STAT3 is an essential pathway in mediating the effects of IL-22 secreted by NKp44+NK cells on the proliferation of FLS in patients with RA.

The role of transforming growth factor β signaling in fibroblast-like synoviocytes from patients with oligoarticular juvenile idiopathic arthritis: dysregulation of transforming growth factor β signaling, including overexpression of bone morphogenetic protein 4, may lead to a chondrocyte phenotype and may contribute to bony hypertrophy

OBJECTIVE

This study was designed to investigate the pathogenic contributions of fibroblast-like synoviocytes (FLS) to juvenile idiopathic arthritis (JIA) by identifying pathways with dysregulated gene expression in FLS from patients with oligoarticular JIA.

METHODS

FLS were derived from synovial fluid obtained by arthrocentesis from patients with JIA undergoing intraarticular steroid injections and from orthopedic control patients. Gene expression profiles of the JIA and control FLS were obtained using the Affymetrix platform, with application of Ingenuity Pathway Analysis and Gene Set Enrichment Analysis software to define gene sets in dysregulated pathways and networks of potential pathologic relevance in this disease. Biologically relevant differentially expressed genes were confirmed by RNA and protein analysis.

RESULTS

Exploration of global gene expression profiles of the JIA FLS revealed important dysregulated pathways, including the transforming growth factor β (TGFβ) signaling, as well as endochondral bone formation, cartilage formation, and β-catenin networks. Importantly, bone morphogenetic protein 4 (BMP-4) was significantly overexpressed in the JIA FLS. FLS from patients with oligoarticular JIA exhibit a chondrocyte phenotype, as evidenced by expression of type II collagen and aggrecan.

CONCLUSION

Dysregulation of the pathways involved in the pathogenesis of oligoarticular JIA were revealed through gene expression profiling. JIA FLS displayed dysregulated TGFβ signaling and exhibited a hypertrophic chondrocyte phenotype. These characteristics, along with contributions from the β-catenin network may have implications for endochondral bone formation and local growth disturbances in oligoarticular JIA. Overexpression of BMP-4 in FLS from patients with oligoarticular JIA in particular may play an important role in disease pathogenesis, with a direct effect on functional outcome and with implications for future treatment.

Therapeutic efficacy of three bispecific antibodies on collagen-induced arthritis mouse model

Interleukin-1β (IL-1β) and interleukin-17A (IL-17A) are inducible factors and important cytokines in the pathogenesis of rheumatoid arthritis (RA). In the present study, three bispecific and neutralizing antibodies (BsAB-1, BsAB-2 and BsAB-3) against both hIL-1β and hIL-17A were constructed, their therapeutic efficacy was compared on collagen induced arthritis (CIA) model mice. In vitro assays demonstrated that the three antibodies could simultaneously bind to target both hIL-1β and hIL-17A. Mice with CIA were subcutaneously administered with one of three antibodies every two days for 29 days, we noticed that, compared with the BsAB-2 and BsAB-3, BsAB-1 antibody therapy resulted in more significant effect on alleviating the severity of arthritis by preventing bone damage and cartilage destruction and substantially decreasing production of CII-specific antibodies. In addition, BsAB-1 antibody was more potent in the inhibition of mRNA expression of IL-2, IL-1β, IL-17A, TNF-α and MMP-3 in the spleen of CIA mice compared to the other two. In summary, BsAB-1 is superior over BsAB-2 and BsAB-3 for the treatment of RA model mice, and may be chosen as an ideal candidate for further development of therapeutic drugs for treatment of RA.

Celastrol induced DNA damage, cell cycle arrest, and apoptosis in human rheumatoid fibroblast-like synovial cells

Celastrol is one of the principal active ingredients of Tripterygium wilfordii Hook.f., a toxic Chinese medical herb traditionally prescribed for controlling pain and inhibiting inflammation in various chronic inflammatory diseases, including rheumatoid arthritis (RA). Resistance to apoptosis of fibroblast-like synoviocytes is considered a major characteristic of RA. In this study, we test celastrol's cytotoxic effect and potential mechanisms in human rheumatoid synovial fibroblasts (RA-FLS). In the cytotoxic assay, we found that celastrol dose-dependently decreased RA-FLS viability and increased LDH release. The apoptotic nuclear morphology was observed after celastrol treatment as determined by DAPI fluorescence staining. Flow cytometry analysis with PI and Annexin V revealed that celastrol induced RA-FLS cell cycle arrest in the G2/M phase and apoptosis. Furthermore, celastrol dramatically increased expression of Bax/Bcl-2, proteolytic cleavage of Caspase-3, -9, PARP, and decreased expression of FasR. In addition, celastrol treatment resulted in DNA damage. Collectively, we concluded that celastrol inhibits RA-FLS proliferation by inducing DNA damage, cell cycle arrest, and apoptosis in vitro, which might provide data for its application in RA treatment.

Norisoboldine alleviates joint destruction in rats with adjuvant-induced arthritis by reducing RANKL, IL-6, PGE(2), and MMP-13 expression

AIM

To explore the effects of norisoboldine (NOR), a major isoquinoline alkaloid in Radix Linderae, on joint destruction in rats with adjuvant-induced arthritis (AIA) and its underlying mechanisms.

METHODS

AIA was induced in adult male SD rats by intradermal injection of Mycobacterium butyricum in Freund's complete adjuvant at the base of the right hind paw and tail. From d 14 after immunization, the rats were orally given NOR (7.5, 15, or 30 mg/kg) or dexamethasone (0.5 mg/kg) daily for 10 consecutive days. Joint destruction was evaluated with radiological scanning and H&E staining. Fibroblast-like synoviocytes (FLS) were prepared from fresh synovial tissues in the AIA rats. The expression of related proteins and mRNAs were detected by ELISA, Western blotting and RT-PCR.

RESULTS

In AIA rats, NOR (15 and 30 mg/kg) significantly decreased the swelling of paws and arthritis index scores, and elevated the mean body weight. NOR (30 mg/kg) prevented both the infiltration of inflammatory cells and destruction of bone and cartilage in joints. However, NOR (15 mg/kg) only suppressed the destruction of bone and cartilage, but did not obviously ameliorate synovial inflammation. NOR (15 and 30 mg/kg) significantly decreased the serum levels of receptor activator of nuclear factor κB ligand (RANKL), IL-6, PGE2, and MMP-13, but not the osteoprotegerin and MMP-1 levels. The mRNA levels of RANKL, IL-6, COX-2, and MMP-13 in synovium were also suppressed. Dexamethasone produced similar effects in AIA rats as NOR did, but without elevating the mean body weight. In the cultured FLS, treatment with NOR (10 and 30 mmol/L) significantly decreased the secretion of RANKL, IL-6, PGE2, and MMP-13 proteins. Furthermore, the treatment selectively prevented the activation of MAPKs, AKT and transcription factor AP-1 component c-Jun, but not the recruitment of TRAF6 or the activation of JAK2/STAT3. Treatment of the cultured FLS with the specific inhibitors of p38, ERK, AKT, and AP-1 significantly decreased the secretion of RANKL, IL-6, PGE2, and MMP-13 proteins.

CONCLUSION

NOR can alleviate joint destruction in AIA rats by reducing RANKL, IL-6, PGE2, and MMP-13 expression via the p38/ERK/AKT/AP-1 pathway.

The Predicted Proteomic Network Associated with the Antiarthritic Action of Qingfu Guanjieshu in Collagen-II-Induced Arthritis in Rats

Qingfu Guanjieshu (QFGJS) is an herbal preparation for treating rheumatoid arthritis (RA). Previous studies revealed that QFGJS significantly inhibited experimental arthritis and acute inflammation, accompanied by reduction of proinflammatory cytokines and elevation of anti-inflammatory cytokines. This study aims to identify the targeted proteins and predict the proteomic network associated with the drug action of QFGJS by using 2D gel and MALDI-TOF-MS/MS techniques. Thirty female Wistar rats were evenly grouped as normal and vehicle- and QFGJS-treated CIA rats. The antiarthritic effect of QFGJS was examined with a 19-day treatment course, and the knee synovial tissues of animals from each group were obtained for 2D gel and MALDI-TOF-MS/MS analysis. Results showed that QFGJS significantly ameliorated collagen II-induced arthritis when administrated at 2.8 g/kg body weight for 19 days. 2D gel image analysis revealed 89 differentially expressed proteins in the synovial tissues among the normal and vehicle- and QFGJS-treated CIA rats from over 1000 proteins of which 63 proteins were identified by MALDI-TOF-MS/MS analysis, and 32 proteins were included for classification of functions using Gene Ontology (GO) method. Finally, 14 proteins were analyzed using bioinformatics, and a predicted proteomic network related to the anti-arthritic effect of QFGJS was established, and Pgk1 plays a central role.

The role of Raf kinase inhibitor protein in rheumatoid fibroblast-like synoviocytes invasiveness and cytokine and matrix metalloproteinase expression

Fibroblast-like synoviocytes (FLS) play an important role in the pathogenesis of rheumatoid arthritis. Raf kinase inhibitor protein (RKIP) negatively regulates the Raf/MEK/ERK and NF-κB pathway. The role of RKIP in rheumatoid FLS is unknown. The purpose of the present study was to investigate the function of RKIP in rheumatoid FLS. Rheumatoid FLS were transfected with either RKIP-expressing plasmids or RKIP small interfering RNA (siRNA). RKIP protein was detected in rheumatoid synovial tissue (ST) and FLS. RKIP overexpression significantly decreased IL-6 mRNA expression in TNF-α-stimulated rheumatoid FLS. RKIP overexpression also showed a decreased trend in IL-8, MMP-1, and MMP-3 mRNA expression in TNF-α-stimulated rheumatoid FLS. RKIP silencing resulted in significantly increased MMP-1 and MMP-3 mRNA expression in TNF-α-stimulated rheumatoid FLS. RKIP silencing also increased IL-6 and IL-8 mRNA expression in TNF-α-stimulated rheumatoid FLS, but this increase did not reach statistical significance. TNF-α-induced ERK and NF-κB activation was suppressed in FLS with RKIP overexpression. RKIP silencing resulted in a significantly higher invasion index in TNF-α-stimulated rheumatoid FLS compared to controls. These results suggest that RKIP might be a potential therapeutic target for rheumatoid arthritis.

Inhibitory Effect of Curcumol on Jak2-STAT Signal Pathway Molecules of Fibroblast-Like Synoviocytes in Patients with Rheumatoid Arthritis

Hyperplasia of synovial membrane in rheumatoid arthritis (RA) is a critical pathological foundation for inducing articular injury. The janus kinase and signal transducer and activator of transcription (Jak-STAT) pathway plays a critical role in synovial membrane proliferation induced by platelet-derived growth factor (PDGF). To explore the anti-cell proliferation mechanism of curcumol, a pure monomer extracted from Chinese medical plant zedoary rhizome, the changes of Jak2-STAT1/3 signal pathway-related molecules in synoviocytes were observed in vitro. In this study, the fibroblast-like synoviocytes (FLS) in patients with RA were collected and cultured. The following parameters were measured: cell proliferation (WST-1 assay), cell cycles (fluorescence-activated cell sorting, FACS), STAT1 and STAT3 activities (electrophoretic mobility shift assay, EMSA), and the protein expressions of phosphorylated Jak2, STAT1, and STAT3 (Western blot). It was shown that curcumol could inhibit the RA-FLS proliferation and DNA synthesis induced by PDGF-BB in a dose-dependent manner in vitro. The transcription factors activities of STAT1 and STAT3 were obviously elevated after PDGF-BB stimulation (P < 0.05). Super-shift experiments identified the STAT1 or STAT3 proteins in the complex. Furthermore, the different concentration curcumol could downregulate the DNA binding activities of STAT1 and STAT3 (P < 0.05) and inhibit the phosphorylation of Jak2 while it had no effect on the protein expressions of STAT1 and STAT3. Positive correlations were found between changes of cell proliferation and DNA-binding activities of STAT1 and STAT3, respectively (P < 0.01). In conclusion, curcumol might suppress the FLS proliferation and DNA synthesis induced by PDGF-BB through attenuating Jak2 phosphorylation, downregulating STAT1 and STAT3 DNA-binding activities, which could provide theoretical foundation for clinical treatment of RA.

Metastatic lymph node 51 and fibroblast-like synoviocyte hyperproliferation in rheumatoid arthritis pathogenesis

One of the varied characteristic features of the pathogenesis of rheumatoid arthritis (RA) is synovial hyperplasia. Fibroblast-like synoviocytes (FLSs) play a key role in the development of sustained inflammation in arthritic joints. We have reported previously that metastatic lymph node 51 (MLN51) is involved in the proliferation of FLSs in the pathogenesis of RA. Interestingly, the overexpression of MLN51 was observed only in RA FLSs, but not in osteoarthritis FLSs, possibly expecting that MLN51 may be a RA-specific marker. Additionally, we found that granulocyte-macrophage colony-stimulating factor signaling activates mitogen-activated protein kinase, followed by the upregulation of MLN51 and FLICE-inhibitory protein, resulting in FLS hyperplasia in RA. Based on these studies, we could be firm that MLN51 is a key factor in FLS hyperplasia of RA patients.

Reduction of interleukin-1β induced matrix metalloproteinase-3 release by extracts of six plants: inhibitory screening of 35 traditional medicinal plants

Rheumatoid arthritis (RA) is a chronic inflammatory joint disease associated with matrix metalloproteinase (MMP)-3, leading to destruction of the cartilage. The objective of this study was to investigate and discuss the suitability of the 35 medicinal plants as therapeutic candidates to treat RA. Fibroblast-like synoviocytes (FLSs), derived from patients with RA, were adjusted to 2 × 10(6) cells/mL in a 24-well plate and pretreated with the distilled water extracts of the 35 plants (1, 10, and 100 µg/mL) for 1 h followed by interleukin-1β (IL-1β) (1 ng/mL) for 24 h. The concentration of MMP-3 was then determined using a Duoset ELISA Kit. The six plants (Artemisiae Capillaris Herba, AC; Bambusae Caulis In Taeniam, BC; Cassiae Semen, CS; Corni Fructus, CF; Leonuri Herba, LH; Schizonepetae Spica, SS) showed no toxicity, including MMP-3. The MMP-3 level was increased by 3.38-fold (212.23 μg/mL) in IL-1β-stimulated FLSs. The IL-1β-induced MMP-3 level was significantly and dose-dependently reduced by >50% by the six plants (P < 0.01: at 100  μg/ mL of CS and LH, P < 0.001: at 10 μg/mL of all plants, and at 100 μg/mL of AC, BC, CF, and SS). This is the first study on the MMP-3 inhibitory effect of the examined plants in FLSs isolated from RA patients. From our original research, the six candidate plants were identified.

Alpinia galanga extracts downregulate interleukin-1β-induced matrix metalloproteinases expression in human synovial fibroblasts

Alpinia galanga has been used as alternative medicine for anti-rheumatic activities. However, the precise action of the extract on arthritic diseases is not yet fully understood. In this study, we investigated the effects of A. galanga extracts on the expression of genes involved in catabolic activities in an interleukin-1β (IL-1β)-induced human synovial fibroblast as an inflammatory model. Confluent primary human synovial fibroblasts were treated for 24 h with A. galanga hexane extracts in the presence of recombinant human IL-1β. MMPs in the culture medium were monitored by gelatin zymography. Total RNA was isolated from the cell lysate and analyzed via semi-quantitative RT-PCR. After treatment with A. galanga extracts, MMP-2 activity in the culture medium was significantly reduced. In addition, MMP-1, MMP-3, MMP-13, and Cox-2 expression were downregulated. These data suggest that the decrease of gene expression and production of MMPs in synovial fibroblasts against inflammatory stimuli could be due to the effects of the A. galanga extracts. Therefore, A. galanga extracts might be a promising therapeutic agent for arthritis.

Expression of β-catenin in rheumatoid arthritis fibroblast-like synoviocytes

OBJECTIVE

β-Catenin is the key mediator of the Wnt signal and also a component of E-cadherin complexes at the intercellular adhering junction, which mediates cell-cell adhesion. We hypothesized that β-catenin might be involved in the long-lasting changed phenotype of rheumatoid arthritis fibroblast-like synoviocytes (RA-FLS) and could play a role in the pathogenesis of RA. In this study we investigated the expression of β-catenin in RA-FLS.

METHODS

Synovial tissues were obtained during joint replacement surgery or arthroscopy from six patients with RA, six patients with osteoarthritis (OA), and six patients with joint trauma (Trauma group). Immunohistochemical analysis of β-catenin was performed in the synovial tissues from the three groups. Synovial tissues from three patients in each group were selected at random for FLS isolation. Expression of β-catenin in FLS from the three groups was evaluated at the protein level by western blotting and at the mRNA level by reverse transcription polymerase chain reaction (RT-PCR).

RESULTS

Immunohistochemistry revealed that the expression of β-catenin in synovial lining cells of the RA samples was significantly greater than that of the OA or trauma samples (p < 0.01). Western blotting and RT-PCR showed that β-catenin expression was elevated in RA-FLS compared with that in OA-FLS or Trauma-FLS (p < 0.05) at the protein level but no difference was found at the mRNA level.

CONCLUSIONS

Expression of β-catenin is elevated in RA-FLS, not only in vitro but also in vivo. The increase is due to activation of Wnt/β-catenin signalling. Wnt/β-catenin signalling is activated in RA-FLS, and contributes to the stable activation of RA-FLS.

Luteolin suppresses IL-1beta-induced cytokines and MMPs production via p38 MAPK, JNK, NF-kappaB and AP-1 activation in human synovial sarcoma cell line, SW982

Matrix metalloproteinases (MMPs) play an important role in tissue degradation in rheumatoid synovium and inflammatory cytokines are essential in the pathogenesis of rheumatoid arthritis (RA). This study was conducted to evaluate the efficacy of luteolin in regulating interleukin-1beta (IL-1beta)-induced production of MMPs (MMP-1 and -3) and cytokines (tumor necrosis factor (TNF)-alpha and IL-6) in human synovial cell line, SW982. Treatment with luteolin at 1 or 10 microM significantly (P<0.05) inhibited IL-1beta-induced MMPs (MMP-1 and -3) and cytokines (TNF-alpha and IL-6) production when measured by enzyme-linked immunosorbent assay (ELISA). The mitogen-activated protein kinases (MAPKs) represent an attractive target for RA because they can regulate MMP and cytokine expression. The effects of luteolin on the activation of MAPKs and transcription factors were also examined in SW982 cells by ELISA. IL-1beta-induced JNK and p38 activation were inhibited by luteolin. Moreover, IL-1beta-induced activator protein-1 (AP-1) and nuclear factor-kappaB (NF-kappaB) activation were inhibited by luteolin. These results suggest that luteolin reduces the production of MMPs and cytokines in SW982 cells by inhibiting MAPKs (JNK and p38) and transcription factors (AP-1 and NF-kappaB).

Inhibition of synovial hyperplasia, rheumatoid T cell activation, and experimental arthritis in mice by sulforaphane, a naturally occurring isothiocyanate

OBJECTIVE

To investigate whether sulforaphane (SFN), an isothiocyanate derived from cruciferous vegetables such as broccoli, regulates synoviocyte hyperplasia and T cell activation in rheumatoid arthritis (RA).

METHODS

Synoviocyte survival was assessed by MTT assay. The levels of Bcl-2, Bax, p53, and pAkt were determined by Western blot analysis. Cytokine concentrations in culture supernatants from mononuclear cells were analyzed by enzyme-linked immunosorbent assay. The in vivo effects of SFN were examined in mice with experimentally induced arthritis.

RESULTS

SFN induced synoviocyte apoptosis by modulating the expression of Bcl-2/Bax, p53, and pAkt. In addition, nonapoptotic doses of SFN inhibited T cell proliferation and the production of interleukin-17 (IL-17) and tumor necrosis factor alpha (TNFalpha) by RA CD4+ T cells stimulated with anti-CD3 antibody. Anti-CD3 antibody-induced increases in the expression of retinoic acid-related orphan receptor gammat and T-bet were also repressed by SFN. Moreover, the intraperitoneal administration of SFN to mice suppressed the clinical severity of arthritis induced by injection of type II collagen (CII), the anti-CII antibody levels, and the T cell responses to CII. The production of IL-17, TNFalpha, IL-6, and interferon-gamma by lymph node cells and spleen cells from these mice was markedly reduced by treatment with SFN. Anti-CII antibody-induced arthritis in mice was also alleviated by SFN injection.

CONCLUSION

SFN was found to inhibit synovial hyperplasia, activated T cell proliferation, and the production of IL-17 and TNFalpha by rheumatoid T cells in vitro. The antiarthritic and immune regulatory effects of SFN, which were confirmed in vivo, suggest that SFN may offer a possible treatment option for RA.

Expression of sphingosine kinase 2 in synovial fibroblasts of rheumatoid arthritis contributing to apoptosis by a sphingosine analogue, FTY720

Gene expression profiles in synovial tissues from rheumatoid arthritis (RA) patients have yielded useful information on the pathogenetic process of the synovitis. In one group of them, sphingosine kinase 2 (SPHK2), a nuclear protein regulating cell proliferation, seemed to be highly expressed, undergoing a different pathogenetic process of synovitis. In the present study it was clarified that SPHK2 was expressed in the synovial fibroblasts of the synovial tissues obtained from the knee joints of the RA patients. In the cultured synovial fibroblasts from these patients, SPHK2 was more highly expressed than that in the human macrophage cell line, THP-1 and human dermal fibroblasts. SPHK2 was expressed in and around the nucleus and transferred to the cytoplasm and cell surface by the administration of epidermal growth factor, associated with the increased expression of sphingosine-1-phosphate. A sphingosine analogue, FTY720, which is activated by phosphorylation specifically by SPHK2, mediated apoptotic signaling of the cultured synovial fibroblasts. These findings suggest that SPHK2 may regulate the autonomous proliferation of synovial fibroblasts as one of the predisposing genes to RA and could be a target for a novel therapeutic strategy for RA.

Adapted Boolean network models for extracellular matrix formation

BACKGROUND

Due to the rapid data accumulation on pathogenesis and progression of chronic inflammation, there is an increasing demand for approaches to analyse the underlying regulatory networks. For example, rheumatoid arthritis (RA) is a chronic inflammatory disease, characterised by joint destruction and perpetuated by activated synovial fibroblasts (SFB). These abnormally express and/or secrete pro-inflammatory cytokines, collagens causing joint fibrosis, or tissue-degrading enzymes resulting in destruction of the extra-cellular matrix (ECM).We applied three methods to analyse ECM regulation: data discretisation to filter out noise and to reduce complexity, Boolean network construction to implement logic relationships, and formal concept analysis (FCA) for the formation of minimal, but complete rule sets from the data.

RESULTS

First, we extracted literature information to develop an interaction network containing 18 genes representing ECM formation and destruction. Subsequently, we constructed an asynchronous Boolean network with biologically plausible time intervals for mRNA and protein production, secretion, and inactivation. Experimental gene expression data was obtained from SFB stimulated by TGFbeta1 or by TNFalpha and discretised thereafter. The Boolean functions of the initial network were improved iteratively by the comparison of the simulation runs to the experimental data and by exploitation of expert knowledge. This resulted in adapted networks for both cytokine stimulation conditions. The simulations were further analysed by the attribute exploration algorithm of FCA, integrating the observed time series in a fine-tuned and automated manner. The resulting temporal rules yielded new contributions to controversially discussed aspects of fibroblast biology (e.g., considerable expression of TNF and MMP9 by fibroblasts stimulation) and corroborated previously known facts (e.g., co-expression of collagens and MMPs after TNFalpha stimulation), but also revealed some discrepancies to literature knowledge (e.g., MMP1 expression in the absence of FOS).

CONCLUSION

The newly developed method successfully and iteratively integrated expert knowledge at different steps, resulting in a promising solution for the in-depth understanding of regulatory pathways in disease dynamics. The knowledge base containing all the temporal rules may be queried to predict the functional consequences of observed or hypothetical gene expression disturbances. Furthermore, new hypotheses about gene relations were derived which await further experimental validation.

Prostaglandin E2 differentially modulates proinflammatory/prodestructive effects of TNF-alpha on synovial fibroblasts via specific E prostanoid receptors/cAMP

The present study investigated the influence of PGE(2), E prostanoid (EP) receptors, and their signaling pathways on matrix metalloproteinase (MMP)-1 and IL-6 expression in synovial fibroblasts (SFs) from rheumatoid arthritis (RA) patients. RASFs expressed all four EP receptors, with selective induction of EP2 by TNF-alpha. TNF-alpha time-dependently increased intracellular cAMP/protein kinase A signaling (maximum, 6-12 h) and PGE(2) secretion (maximum, 24 h). PGE(2) and the EP2 agonists butaprost or ONO-AE1-259 ((16)-9-deoxy-9beta-chloro-15-deoxy-16-hydroxy-17,17-trimethylene-19,20-didehydro PGE(1)), in turn, induced a rapid, time-dependent (maximum, 15-30 min) increase of cAMP. Additionally, cyclooxygenase-2 inhibition by NS-398 (N-(2-cyclohexyloxy-4-nitrophenyl)-methanesulfonamide) reduced the TNF-alpha-induced increase in IL-6 mRNA/protein, which was restored by stimulation with PGE(2) or EP2, EP3, and EP4 agonists. In contrast, TNF-alpha-induced MMP-1 secretion was not influenced by NS-398 and diminished by PGE(2) via EP2. Finally, 3-isobutyl-1-methylxanthine enhanced the effects of PGE(2) on MMP-1, but not on IL-6 mRNA. In conclusion, PGE(2) differentially affects TNF-alpha-induced mRNA expression of proinflammatory IL-6 and prodestructive MMP-1 regarding the usage of EP receptors and the dependency on cAMP. Although specific blockade of EP2 receptors is considered a promising therapeutic strategy in RA, opposite regulation of proinflammatory IL-6 and prodestructive MMP-1 by PGE(2) via EP2 may require more complex approaches to successfully inhibit the cyclooxygenase-1/2 cAMP axis.