The role of high‐mobility group box protein 1 in collagen antibody‐induced arthritis is dependent on vascular endothelial growth factor

High‐mobility group box 1 (HMGB1) has been implicated in angiogenesis and rheumatoid arthritis (RA). The aim of this study was to define more clearly the role of HMGB1 in the synovial angiogenesis and pathogenesis of an immune model of arthritis. BALB/c mice were injected with monoclonal anti‐collagen antibody cocktail followed by lipopolysaccharide to induce arthritis. HMGB1 and vascular endothelial growth factor (VEGF) were over‐expressed in the areas of the synovium where more inflammation and neoangiogenesis were present. The selective blockade of HMGB1 or VEGF resulted alternatively in a lower severity of arthritis evaluated by the arthritis index. Furthermore, exogenous HMGB1 administration caused a worsening of arthritis, associated with VEGF up‐regulation and increased synovial angiogenesis. The selective inhibition of VEGF also resulted in no induction of arthritis in mice receiving exogenous HMGB1. Cytokine enzyme‐linked immunosorbent assay (ELISA) analyses performed on peripheral blood and synovial fluid demonstrated a significant reduction of interleukin (IL)?1β, IL‐6 and tumour necrosis factor (TNF)‐α in mice where HMGB1 and VEGF pathways were blocked. Interestingly, the selective blockade of HMGB1 and VEGF resulted in an increase of the peripheral IL‐17A concentration. The development of arthritis mediated by HMGB1 and the synovial angiogenesis can be blocked by inhibiting the VEGF activity. The proinflammatory and proangiogenic cytokine IL‐17A was increased when HMGB1 is inhibited, but the synovial angiogenesis was nevertheless reduced in this model of arthritis. Taken together, these findings shed new light on the role of this nuclear protein in the pathogenesis of arthritis in an RA‐like model.     

Regulation of Joint Destruction and Inflammation by p53 in Collagen-Induced Arthritis

The role of the tumor suppressor p53 as a key regulator of inflammation was examined in murine collagen-induced arthritis (CIA), a model of rheumatoid arthritis. Wild-type DBA/1 mice develop progressive arthritis in this model, in which p53 expression and apoptosis are evident in the synovial cells. In contrast, the joints of p53(-/-) DBA/1 animals with CIA showed increased severity of arthritis using clinical and histological scoring methods with almost no apoptosis. Consistent with this, collagenase-3 expression and cytokine production (interleukin-1 and interleukin-6) in the joints of p53(-/-) mice with CIA were significantly greater than in wild-type mice. Anti-collagen antibody titers, however, were not different. Therefore, p53 expression occurs during inflammation and acts to suppress local inflammatory responses. Because mutations in p53 have been described in the synovial membrane of rheumatoid arthritis patients, the loss of p53 function in synoviocytes or other cells in the joint because of dominant-negative mutations might contribute to invasion and destruction of the joint in this disease.     

A novel model of fibroblast-mediated cartilage destruction

In rheumatoid arthritis (RA), fibroblasts have been shown to be crucial for disease progression as well as joint destruction. In the model of human/murine SCID arthritis, synovial explants as well as fibroblasts from human rheumatoid synovial membrane induce destructive arthritis in immunodeficient mice. Hereby, the underlying cartilage destruction is accomplished by murine fibroblasts. Therefore, murine destructive fibroblasts represent a promising tool to investigate destruction of articular cartilage and bone. In this context, a novel destructive murine fibroblast line (LS48) was examined for morphological, ultrastructural, immunological and functional cellular parameters. These cells were injected into knees of SCID mice. Subsequently, the animals were monitored for joint swelling and serological parameters of arthritis by radiological methods. Finally, cartilage destruction was assessed morphologically. Cultured LS48 cells exhibit characteristic features that resemble those of activated synovial fibroblasts in human RA. Expression levels of inducible nitric oxide synthase, interleukin-6, tumour necrosis factor-alpha and matrix metalloproteinases were comparable to those detected in invasive human fibroblasts. The instillation of 5 x 10(5) LS48 cells into the knee joints of SCID mice initiated a rapid progressive process, that caused cartilage destruction within 10 days, and morphological examinations revealed that articular cartilage was infiltrated by the fibroblasts injected previously. In summary, the intra-articular application of LS48 cells represents a rapid and highly reproducible model to investigate the initiation and progression of cartilage destruction in connection with RA therapy and represents an easy-to-handle animal model.     

Transfer of type II collagen-induced arthritis from DBA/1 to severe combined immunodeficiency mice can be prevented by blockade of Mac-1.

Collagen-induced arthritis in susceptible mice is widely accepted as an experimental model for human rheumatoid arthritis (RA). We have investigated the role of the Mac-1 integrin beta 2 in the development and maintenance of arthritis by means of in vivo administration of 5C6 monoclonal antibody (mAb) to block this receptor. Injection of a single dose of 5C6 mAb (0.5 mg, intraperitoneally) prior to the expected onset of collagen-induced arthritis in DBA/1 mice diminished the severity of subsequent disease in these animals, as assessed both clinically and histologically (P < 0.01, chi 2). In the DBA/1 to severe combined immunodeficiency (SCID) transfer model of arthritis, the incidence of clinical arthritis was significantly reduced in SCID mice receiving maintained 5C6 treatment commencing the day prior to administration of donor splenocytes. Histological evaluation of joints from animals without clinically evident arthritis confirmed the absence of an inflammatory infiltrate in 22/27 joints examined. In a minority of these joints, however, synovial hyperplasia was apparent. In contrast, delaying antibody administration until 10 days after donor spleen cell transfer failed to protect three of five SCID recipients. These results confirm a functional role for Mac-1 in the generation of collagen-induced arthritis in mice. Since mAb 5C6 is non-cytotoxic, its action must be by blockade of the interactions between Mac-1 and its natural ligand(s). Our findings support the hypothesis that cells expressing Mac-1 play an important role in the induction and maintenance of joint damage in collagen-induced arthritis.     

S100A4 (Mts1): is there any relation to the pathogenesis of rheumatoid arthritis?

S100A4 (Mts1) belongs to the S100 family of calcium binding proteins, which are involved in diverse biological regulatory activities. An association between S100A4 and tumor progression has been demonstrated in several studies. S100A4 binds to distinct intracellular target proteins and regulates specific functions involved in tumor progression such as cell motility, proliferation and apoptosis as well as remodelling of the extracellular matrix. Once released from the tumor or tumor-activated stromal cells, it may influence certain functions of target cells towards a more aggressive phenotype. Extracellular S100A4 has been demonstrated to contribute to angiogenesis and the increased production of matrix-degrading enzymes by both endothelial and tumor cells. Moreover, S100A4 might be responsible for TCRgammadelta T-cell mediated lysis and negative regulation of matrix mineralization. Increased expression of S100A4 mRNA has recently been found in proliferating rheumatoid arthritis synovial fibroblasts and synovial tissues from rheumatoid arthritis patients. Synovial hyperplasia in rheumatoid arthritis consists of inflammatory cells and activated synovial lining cells which contribute to the progressive destruction of the joints during the disease. Since several phenomena are similar between rheumatoid arthritis and malignant tumors it can be hypothesized that S100A4 contributes to the invasive and tumor-like behavior of rheumatoid arthritis synovium.     

NF‐κB‐inducing kinase is a key regulator of inflammation‐induced and tumour‐associated angiogenesis

Angiogenesis is essential during development and in pathological conditions such as chronic inflammation and cancer progression. Inhibition of angiogenesis by targeting vascular endothelial growth factor (VEGF) blocks disease progression, but most patients eventually develop resistance which may result from compensatory signalling pathways. In endothelial cells (ECs), expression of the pro‐angiogenic chemokine CXCL12 is regulated by non‐canonical nuclear factor (NF)‐κB signalling. Here, we report that NF‐κB‐inducing kinase (NIK) and subsequent non‐canonical NF‐κB signalling regulate both inflammation‐induced and tumour‐associated angiogenesis. NIK is highly expressed in endothelial cells (ECs) in tumour tissues and inflamed rheumatoid arthritis synovial tissue. Furthermore, non‐canonical NF‐κB signalling in human microvascular ECs significantly enhanced vascular tube formation, which was completely blocked by siRNA targeting NIK. Interestingly, Nik^?/? mice exhibited normal angiogenesis during development and unaltered TNFα‐ or VEGF‐induced angiogenic responses, whereas angiogenesis induced by non‐canonical NF‐κB stimuli was significantly reduced. In addition, angiogenesis in experimental arthritis and a murine tumour model was severely impaired in these mice. These studies provide evidence for a role of non‐canonical NF‐κB signalling in pathological angiogenesis, and identify NIK as a potential therapeutic target in chronic inflammatory diseases and tumour neoangiogenesis. © 2014 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.     

Hypoxia augments cytokine (transforming growth factor-beta (TGF-β) and IL-1)-induced vascular endothelial growth factor secretion by human synovial fibroblasts

Vascular endothelial growth factor (VEGF) is abundant in synovium and synovial fluids, where it probably contributes to vascular permeability and angiogenesis in arthritic joints. To investigate the probable sources of VEGF in synovium, we compared the ability of several cytokines (TGF-β, platelet-derived growth factor (PDGF), IL-1, tumour necrosis factor (TNF), basic fibroblast growth factor (bFGF) that are associated with arthritis and angiogenesis, to stimulate secretion of VEGF protein by human synovial fibroblasts. TGF-β was the strongest inducer of VEGF secretion; six times more VEGF was secreted when cells were stimulated by TGF-β than when stimulated by PDGF or IL-1 for 24 h. TNF-α and bFGF did not stimulate any secretion of VEGF. The stimulatory effects of TGF-β and IL-1 on VEGF secretion were additive. Hypoxic culture alone also stimulated VEGF secretion, but more importantly, hypoxic culture conditions doubled the rate of VEGF secretion stimulated by the cytokines TGF-β and IL-1. When dermal and synovial fibroblasts were stimulated identically by hypoxia and cytokines (TGF-β and IL-1), synovial fibroblasts secreted four times more VEGF than did dermal fibroblasts. Thus in rheumatoid arthritis, the capacity of synovial fibroblasts in the hypoxic environment to secrete large amounts of VEGF in response to cytokines such as TGF-β probably contributes significantly to angiogenesis in the synovium.     

Metabolic alterations in the synoviocytes in chronically inflamed knee joints in immune arthritis in the rabbit: comparison with rheumatoid arthritis

The metabolism of the synovial lining cells of the normal and chronically inflamed joints of rabbits, in the Dumonde and Glynn model of rheumatoid arthritis, has been examined by quantitative cytochemistry. Significant alterations in metabolic activity were found in the synovial lining cells of the chronically inflamed joints. These alterations in metabolic activity closely resemble the pattern of metabolic changes found in human synovial lining cells in rheumatoid arthritis.     

Metabolic alterations in the synoviocytes in chronically inflamed knee joints in immune arthritis in the rabbit: comparison with rheumatoid arthritis.

The metabolism of the synovial lining cells of the normal and chronically inflamed joints of rabbits, in the Dumonde and Glynn model of rheumatoid arthritis, has been examined by quantitative cytochemistry. Significant alterations in metabolic activity were found in the synovial lining cells of the chronically inflamed joints. These alterations in metabolic activity closely resemble the pattern of metabolic changes found in human synovial lining cells in rheumatoid arthritis.     

The vasculature in rheumatoid arthritis: cause or consequence?

The expansion of the synovial lining of joints in rheumatoid arthritis (RA) necessitates an increase in the vascular supply to the synovium, to cope with the increased requirement for oxygen and nutrients. New blood vessel formation –'angiogenesis'– is recognized as a key event in the formation and maintenance of the pannus in RA, suggesting that targeting blood vessels in RA may be an effective future therapeutic strategy. Although many pro-angiogenic factors have been demonstrated to be expressed in RA synovium, vascular endothelial growth factor (VEGF) has been demonstrated to a have a central involvement in the angiogenic process in RA. Nevertheless, it is unclear whether angiogenesis – whether driven by VEGF and/or other factors – should be considered as a 'cause' or 'consequence' of disease. This ongoing 'chicken vs. egg' debate is difficult, as even the success of angiogenesis inhibition in models of RA does not provide a direct answer to the question. This review will focus on the role of the vasculature in RA, and the contribution of different angiogenic factors in promoting disease. Although no data regarding the effectiveness of anti-angiogenic therapy in RA have been reported to date, the blockade of angiogenesis nevertheless looks to be a promising therapeutic avenue.     

SUMO-Conjugating Enzyme UBC9 Promotes Proliferation and Migration of Fibroblast-like Synoviocytes in Rheumatoid Arthritis

Rheumatoid arthritis (RA) is a chronic autoimmune disease with high morbidity and mortality. Fibroblast-like synoviocytes (FLS) in the synovial tissues play critical roles in joint destruction. Recent studies implicate the sumoylation in the regulation of the inflammation and arthritis. Thus, we explored whether SUMO-conjugating enzyme UBC9 is involved in the progression of RA using a mouse collagen-induced arthritis (CIA) model. The effects of UBC9 siRNA on cell invasion and migration in human RA-FLS were also assessed in vitro. Treatment with siRNA against UBC9 for 3 weeks reduced the arthritis score and joint destruction. The expression of SUMO-1 and UBC9 protein in CIA joints was inhibited by UBC9 knockdown. Serum levels of anti-collagen (CII) antibodies, vascular endothelial growth factor A (VEGF-A), matrix metalloproteinases (MMP)-3, and MMP-9 were also decreased in CIA mice. In vitro, UBC9 silencing inhibited the secretion of VEGF-A, MMP-3, and MMP-9 from TNF-α-stimulated human RA-FLS. TNF-α-induced RA-FLS proliferation and migration were significantly attenuated by UBC9 knockdown. These findings indicate that SUMO-conjugating enzyme UBC9 promotes proliferation and migration of fibroblast-like synoviocytes in rheumatoid arthritis. Inhibition of UBC9 activity may be a viable therapeutic target in amelioration of disease progression in RA by attenuating FLS proliferation, migration, and invasion.     

Expression of vascular endothelial growth factor by synovial fluid neutrophils in rheumatoid arthritis (RA)

Most of the leucocytes infiltrating rheumatoid synovial fluid (SF) are neutrophils capable of producing a variety of inflammatory mediators known to contribute significantly to the disease process during active RA. In the present study, we investigated the contribution made by SF neutrophils to the elevated levels of vascular endothelial growth factor (VEGF) seen in rheumatoid SF. Rheumatoid SF neutrophils were found to contain significantly larger amounts of both VEGF protein and its mRNA than peripheral blood neutrophils from either RA patients or healthy controls. Levels of cell-associated VEGF were well correlated with free VEGF in SF, which was significantly higher than in SF from osteoarthritis patients. Levels of SF neutrophil-associated VEGF also correlated with RA disease activity and cell surface integrin expression. Thus, SF neutrophil-associated VEGF may be considered an indicator of both local and systemic inflammation of RA, contributing to the neovascularization seen during RA synovitis.     

The recently identified hexosaminidase D enzyme substantially contributes to the elevated hexosaminidase activity in rheumatoid arthritis

Since the 1970s, numerous reports have described elevated hexosaminidase activities in rheumatoid arthritis. However, due to the overlapping substrate specificities of different hexosaminidases, identification of the exact enzyme(s) responsible for the elevated activity remains incomplete.In this work we tested if the recently described enzyme, hexosaminidase D was expressed in human arthritic joints, and could contribute to the elevated hexosaminidase activity in rheumatoid arthritis.Thermostable β-d-N-acetyl-galactosaminidase (hexosaminidase D) activities were determined in synovial fluid samples, synovial membranes, synovial fibroblast cell strains and synovial fibroblast-derived extracellular vesicles of patients with rheumatoid arthritis and osteoarthritis using chromogenic substrates. Expression of the HEXDC gene was detected both in steady state and in TGF-β treated synovial fibroblasts by real time PCR.Strikingly, hexosaminidase D accounted for approximately 50% of the total β-N-acetyl-galactosaminidase activity in synovial membranes and synovial fibroblasts, and it was responsible for the vast majority of the β-d-N-acetyl-galactosaminidase activity in synovial fluid samples. TGF-β downregulated the expression of hexosaminidase D in synovial fibroblasts dose-dependently. Of note, significant activity of hexosaminidase D was also found in association with extracellular vesicles released by synovial fibroblasts.This first study that describes the expression and disease relevance of the HEXDC gene in humans demonstrates the expression of this novel enzyme within the joints, and suggests that its activity may significantly contribute to the overall local exoglycosidase activity.     

TGF-beta type I receptor kinase inhibitor down-regulates rheumatoid synoviocytes and prevents the arthritis induced by type II collagen antibody

Rheumatoid arthritis (RA) is characterized by hypertrophic synovial tissues comprising excessively proliferating synovial fibroblasts and infiltrating inflammatory cells. Transforming growth factor-beta (TGF-beta) is a multifunctional cytokine that regulates cell growth, inflammation and angiogenesis by acting on various cell types. In RA synovial tissues, TGF-beta is expressed at high levels. However, the precise role of TGF-beta in RA remains unclear. We herein demonstrated a causal link between the TGF-beta-induced RA synovial cell proliferation and induction of platelet-derived growth factor (PDGF)-AA. In addition, TGF-beta induced IL-6 and vascular endothelial growth factor (VEGF) production by RA synovial fibroblasts associated with nuclear factor-kappa B activation. These effects of TGF-beta on RA synovial fibroblasts were suppressed by TGF-beta type I receptor kinase inhibitor HTS466284. Furthermore, HTS466284 significantly prevented anti-collagen type II antibody-induced arthritis in mice according to the clinical manifestations, histology, tumor necrosis factor-alpha, PDGF and VEGF expression and 5-bromo-2'-deoxyuridine incorporation. These in vitro and in vivo results suggest that TGF-beta plays a role in the development of synovial hyperplasia consisting of synovial cell proliferation, inflammation and angiogenesis. The blockade of TGF-beta signaling may thus become an additional strategy for the treatment of RA.     

CD147分子通过VEGF促进类风湿关节炎滑膜组织中的血管新生

目的观察类风湿关节炎(RA)滑膜组织中CD147表达强度与血管内皮生长因子(VEGF)表达水平间的相关性,并探讨成纤维样滑膜细胞(FLS)表面CD147的水平变化对VEGF表达的影响。方法收集15例RA患者滑膜,以4例骨关节炎(OA)患者滑膜作对照,采用免疫组织化学SP染色方法检测滑膜组织中CD147和VEGF的表达;体外原代培养FLS细胞,分别加入CD147抗体,PI3K通路阻断剂,MAPK通路的ERK1/2、P38及JNK阻断剂等作用FLS细胞,ELISA检测细胞培养上清中VEGF的表达水平。结果与4例OA滑膜组织CD147和VEGF表达相比,15例RA滑膜组织中均有CD147、VEGF均高表达。其中,表达CD147的细胞主要为成纤维样滑膜细胞、单核-巨噬细胞和淋巴细胞;表达VEGF的细胞主要为成纤维样滑膜细胞、微血管周围成纤维样细胞及血管平滑肌细胞。滑膜组织中CD147和VEGF的表达强度间具有统计学意义。ELISA结果显示,在使用LY294002或抗HAb18GmAb阻断CD147表达后,VEGF的表达量显著下降(P<0.05);而MAPK阻断剂(PD98059、SP600125和SB203580)等对VEGF表达水平无统计学意义(P>0.05)。结论CD147经PI3K-Akt信号通路在RA滑膜组织中上调VEGF促进血管新生。提示CD147在RA血管新生和血管翳形成中有重要意义。     

Production of interleukin 1 in the joint during the development of antigen-induced arthritis in the rabbit.

Antigen-induced arthritis in the rabbit closely resembles rheumatoid arthritis. The levels of interleukin 1 (IL-1) in the synovial fluid and the synthesis of IL-1 by infiltrating cells in synovial fluid and by the synovial lining from control and inflamed joints has been assessed during the first month of this disease. A number of biological assays have been used to measure rabbit IL-1. Of these, only the assay using the murine thymoma cell line (EL-4 NOB-1) was able to detect IL-1 activity in the synovial fluid of arthritic joints, which was present only in the very early lesion. The leucocytes infiltrating the synovial cavity produced little IL-1 ex vivo in the acute lesion but released large amounts when arthritis was established. A similar finding was made with respect to the production of IL-1 by the synovial lining.     

A novel selective spleen tyrosine kinase inhibitor SKI-O-703 (cevidoplenib) ameliorates lupus nephritis and serum-induced arthritis in murine models

Spleen tyrosine kinase (Syk) plays a pivotal role in the activation of B cells and innate inflammatory cells by transducing immune receptor-triggered signals. Dysregulated activity of Syk is implicated in the development of antibody-mediated autoimmune diseases including systemic lupus erythematosus (SLE) and rheumatoid arthritis, but the effect of Syk inhibition on such diseases remains to be fully evaluated. We have developed a novel selective Syk inhibitor, SKI-O-592, and its orally bioavailable salt form, SKI-O-703 (cevidoplenib). To examine the efficacy of SKI-O-703 on the progression of SLE, New Zealand black/white mice at the autoimmunity-established phase were administrated orally with SKI-O-703 for 16 weeks. Levels of IgG autoantibody, proteinuria, and glomerulonephritis fell significantly, and this was associated with hypoactivation of follicular B cells via the germinal center. In a model of serum-transferred arthritis, SKI-O-703 significantly ameliorated synovitis, with fewer neutrophils and macrophages infiltrated into the synovial tissue. This effect was recapitulated when mice otherwise refractory to anti-TNF therapy were treated by TNF blockade combined with a suboptimal dose of SKI-O-703. These results demonstrate that the novel selective Syk inhibitor SKI-O-703 attenuates the progression of autoantibody-mediated autoimmune diseases by inhibiting both autoantibody-producing and autoantibody-sensing cells.