Inhibitory effects of anti-rheumatic drugs on vascular endothelial growth factor in cultured rheumatoid synovial cells

Systematic Review: Targeted Molecular Imaging of Angiogenesis and Its Mediators in Rheumatoid Arthritis

Extensive angiogenesis is a characteristic feature in the synovial tissue of rheumatoid arthritis (RA) from a very early stage of the disease onward and constitutes a crucial event for the development of the proliferative synovium. This process is markedly intensified in patients with prolonged disease duration, high disease activity, disease severity, and significant inflammatory cell infiltration. Angiogenesis is therefore an interesting target for the development of new therapeutic approaches as well as disease monitoring strategies in RA. To this end, nuclear imaging modalities represent valuable non-invasive tools that can selectively target molecular markers of angiogenesis and accurately and quantitatively track molecular changes in multiple joints simultaneously. This systematic review summarizes the imaging markers used for single photon emission computed tomography (SPECT) and/or positron emission tomography (PET) approaches, targeting pathways and mediators involved in synovial neo-angiogenesis in RA.

Dexamethasone Inhibits the Pro-Angiogenic Potential of Primary Human Myoblasts

Tissue regeneration depends on the complex processes of angiogenesis, inflammation and wound healing. Regarding muscle tissue, glucocorticoids (GCs) inhibit pro-inflammatory signalling and angiogenesis and lead to muscle atrophy. Our hypothesis is that the synthetic GC dexamethasone (dex) impairs angiogenesis leading to muscle atrophy or inhibited muscle regeneration. Therefore, this study aims to elucidate the effect of dexamethasone on HUVECs under different conditions in mono- and co-culture with myoblasts to evaluate growth behavior and dex impact with regard to muscle atrophy and muscle regeneration. Viability assays, qPCR, immunofluorescence as well as ELISAs were performed on HUVECs, and human primary myoblasts seeded under different culture conditions. Our results show that dex had a higher impact on the tube formation when HUVECs were maintained with VEGF. Gene expression was not influenced by dex and was independent of cells growing in a 2D or 3D matrix. In co-culture CD31 expression was suppressed after incubation with dex and gene expression analysis revealed that dex enhanced expression of myogenic transcription factors, but repressed angiogenic factors. Moreover, dex inhibited the VEGF mediated pro angiogenic effect of myoblasts and inhibited expression of angiogenic inducers in the co-culture model. This is the first study describing a co-culture of human primary myoblast and HUVECs maintained under different conditions. Our results indicate that dex affects angiogenesis via inhibition of VEGF release at least in myoblasts, which could be responsible not only for the development of muscle atrophy after dex administration, but also for inhibition of muscle regeneration after vascular damage.

Platelet-Released Growth Factors Modulate the Secretion of Cytokines in Synoviocytes under Inflammatory Joint Disease

The etiology and pathogenesis of rheumatoid arthritis (RA) are marked by a complex interplay of various cell populations and is mediated by different signaling pathways. Traditionally, therapies have primarily focused on pain relief, reducing inflammation and the recovery of joint function. More recently, however, researchers have discussed the therapeutic efficacy of autologous platelet-rich plasma (PRP). The main objective of this work is to examine the influences of platelet-released growth factor (PRGF) on human synoviocytes under inflammatory conditions. Additionally, it is checked to which extend treatment with platelet concentrate influences the release of cytokines form synoviocytes. For this purpose, an in vitro RA model was created by stimulating the cells with the TNF-α. The release of cytokines was measured by ELISA. The cytokine gene expression was analyzed by real-time PCR. It has been observed that the stimulation concentration of 10 ng/ml TNF-α resulted in a significantly increased endogenous secretion and gene expression of IL-6 and TNF-α. The anti-inflammatory effect of PRGF could be confirmed through significant reduction of TNF-α and IL-1β. An induced inflammatory condition seems to cause PRGF to inhibit the release of proinflammatory cytokines. Further study is required to understand the exact effect mechanism of PRGF on synoviocytes.

Targeting synovial neoangiogenesis in rheumatoid arthritis

In Rheumatoid arthritis (RA), neoangiogenesis is an early and crucial event to promote the development of the hyperplasic proliferative pathologic synovium. Endothelial cells are critical for the formation of new blood vessels since they highly contribute to angiogenesis and vasculogenesis. Current therapies in RA target the inflammatory consequences of autoimmune activation and despite major improvements these last years still refractory patients or incomplete responders may be seen raising the point of the need to identify complementary additive and innovative therapies. This review resumes the mechanisms of synovial neoangiogenesis in RA, including recent insights on the implication of vasculogenesis, and the regulation of synovial neoangiogenesis by angiogenic and inflammatory mediators. In line with the recent development of vascular-targeted therapies used in cancer and beyond, we also discuss possible therapeutic implications in RA, in particular the combination of targeted immunotherapies with anti-angiogenic molecules.

Tripterygium wilfordii Inhibiting Angiogenesis for Rheumatoid Arthritis Treatment

Rheumatoid arthritis (RA) is a chronic inflammatory disease with a serious pre-vascular inflammatory phase, followed by significant increase in vessel growth. Inhibition of angiogenesis is a novel therapeutic strategy against RA. The Chinese herbal remedy Tripterygium wilfordii, Hook. f. (TwHf) has been reported to be therapeutically efficacious in the treatment of RA. Recent studies have revealed that treatment with TwHf extracts inhibit angiogenesis of RA, thereby elaborately attenuation RA symptom. This review mainly addresses the anti-angiogenesis effect of TwHf in treatment of RA.

T-cell clones from Th1, Th17 or Th1/17 lineages and their signature cytokines have different capacity to activate endothelial cells or synoviocytes

OBJECTIVE

To compare the direct effect of cytokines on synoviocytes and endothelial cells to the effects of supernatants from Th1, Th17 and Th1/17 clones and the direct cell-cell interactions with the same clones.

METHODS

Th17 and Th1/17 clones were obtained from the CD161+CCR6+ fraction and Th1 clones from the CD161-CCR6- fraction of human CD4+ T-cells. Endothelial cells or synoviocytes were cultured in the presence of either isolated pro-inflammatory cytokines (IL-17 and/or TNF-α) or supernatants from the T-cell clones or co-cultured with T-cell clones themselves. IL-6 and IL-8 expression and production were analyzed.

RESULTS

IL-17 and TNF-α induced IL-6 and IL-8 expression, although IL-17 alone had a limited effect on endothelial cells compared to synoviocytes. Supernatants from activated T-helper clones also induced IL-6 and IL-8 expression but with discrepancies between endothelial cells and synoviocytes. Endothelial cells were mostly activated by Th1 clone supernatants whereas synoviocytes were activated by all T-cell subtypes. Finally, cell-cell contact experiments showed a great heterogeneity among cell clones, even from the same lineage. IL-6 expression was mostly induced by contact with Th1 clones both in endothelial and mesenchymal cells whereas IL-8 expression was induced by all T-cell clones whatever their phenotype.

CONCLUSION

We showed that endothelial cells were much more sensitive to Th1 activation whereas synoviocytes were activated by all T-helper lineages. This work highlights the heterogeneity of interactions between T-cells and stromal cells through soluble factors or direct cell contact.

Chronic and non-healing wounds: The story of vascular endothelial growth factor

The pathophysiology of the chronicity and non-healing status of wounds remains unknown. This paper presents the following hypothesis: abnormal patterns of vascular endothelial growth factor receptors (VEGFRs) are the culprits of wound chronicity and non-healing. More specifically, for patients with poor circulation, the decreased VEGFR-2 level is the cause of poor wound healing; for patients with non-compromised circulation, for example, patients with concurrent chronic wounds and active autoimmune diseases, the increased VEGFR-1 level is related to the non-healing status of wounds. The hypothesis is supported by the following facts. VEGFR-1 is the main contributor for inflammation and VEGFR-2 facilitates angiogenesis; soluble VEGFR-1 (sVEGFR-1) inactivates both VEGFR-1 and VEGFR-2. Patients with auto-immune disease have abnormally increased VEGFR-1 and decreased sVEGFR. Wounds in patients with active autoimmune diseases have poor response to electric stimulation which facilitates chronic wound healing in patients without active autoimmune diseases via increasing vascular endothelial growth factor (VEGF) secretion. Patients with chronic wounds (including diabetic foot ulcers and venous leg ulcers) but no active autoimmune diseases have decreased VEGFR-2 levels. We thus believe that abnormal patterns of VEGFRs are the culprits of wound chronicity and non-healing. For wounds with compromised circulation, VEGFR-2 decrease contributes to its chronicity; whereas for wounds with non-compromised circulation, VEGFR-1 increase is the leading cause of the non-healing status of chronic wounds. Treatments and research in wound care should be tailored to target these changes based on circulation status of wounds. Complete elucidation of changes of VEGFRs in chronic and non-healing wounds will enhance our understandings in tissue healing and thus better our selection of appropriate treatments for chronic and non-healing wounds.

Treatment with anti-NAP monoclonal antibody reduces disease severity in murine model of novel angiogenic protein-induced or ovalbumin-induced arthritis

Rheumatoid arthritis (RA) is a polyarticular inflammatory, angiogenic disease. Synovial angiogenesis contributes to inflammation in RA. In this study we have developed an arthritic model in rats using a novel angiogenic protein (NAP), isolated from human synovial fluid of RA patients. We produced anti-NAP monoclonal antibodies (mAbs) and investigated the therapeutic efficacy of the same in adjuvant-induced or NAP-induced arthritis as a model of human RA. The treatment of arthritic rats with anti-NAP mAbs resulted in effective amelioration of paw oedema, radiological arthritic characteristics, serum levels of vascular endothelial growth factor (VEGF) and NAP, compared to that of untreated arthritic animals. Further, profiling of angiogenic markers such as synovial microvessel density, angiogenesis, CD31, VEGF and fms-like tyrosine kinase (Flt1) by immunohistochemistry both in arthritic and anti-NAP mAb-treated animals revealed the efficacy of mAb as an anti-angiogenic functional antibody. Therefore, NAP may be an attractive target to design anti-angiogenic and anti-arthritic therapies to control the pathogenesis of arthritis.

Effects of methotrexate on vascular endothelial growth factor, angiopoietin 1, and angiopoietin 2 in nasal polyps

BACKGROUND

Methotrexate (MTX) is a very effective treatment for chronic inflammatory diseases, which are often associated with increased angiogenesis. Angiogenesis is dependent on a perfectly coordinated balance between endogenous-positive and -negative regulatory factors, including vascular endothelial growth factor (VEGF) and the angiopoietins (Ang). The aim of this study was to investigate the effects of MTX on levels of VEGF, Ang-1, and Ang-2 in organ-cultured nasal polyps (NPs).

METHODS

To determine the effects of MTX, NP tissues were cultured using an air-liquid interface method. Cultures were maintained in the absence or presence of MTX (10 or 100 micromoles) for 24 hours. Hematoxylin and eosin, and TUNEL (terminal deoxynucleotidyl transferase [Tdt]-mediated dUTP-biotin nick-end labeling) staining were performed to observe apoptosis. Enzyme-linked immunosorbent assay was used to quantify tissue concentrations of VEGF, Ang-1, and Ang-2.

RESULTS

MTX treatment resulted in marked alterations in inflammatory cells, especially eosinophils. In contrast, the mucosal epithelium, microvessels including arterioles, veins and capillaries, and fibroblasts maintained their structure. TUNEL(+) cells (apoptotic cells) were seen in the MTX-treated specimens. The more induction of TUNEL(+) cells was observed 100-micromolar MTX-treated specimens. VEGF and Ang-1 levels were significantly lower, and Ang-2 levels were significantly higher in NPs treated with 100-micromolar MTX than in nontreated NPs (p < 0.01).

CONCLUSION

MTX may inhibit the growth of NPs via local regulation of VEGF, Ang-1, and Ang-2 protein levels. We suggest that MTX can be used to treat NPs.

Double anti-angiogenic and anti-inflammatory protein Valpha targeting VEGF-A and TNF-alpha in retinopathy and psoriasis

Pathological angiogenesis usually involves disrupted vascular integrity, vascular leakage, and infiltration of inflammatory cells, which are governed mainly by VEGF-A and TNF-α. Although many inhibitors targeting either VEGF-A or TNF-α have been developed, there is no single inhibitor molecule that simultaneously targets both molecules. Here, we designed and generated a novel chimeric decoy receptor (Valpha) that can simultaneously bind to VEGF-A and TNF-α and block their actions. In this experimental design, we have shown that Valpha, which is an effective synchronous blocker of VEGF-A and TNF-α, can drastically increase treatment effectiveness through its dual-blocking characteristics. Valpha contains the VEGF-A-binding domain of VEGFR1, the TNF-α-binding domain of TNFR2, and the Fc domain of IgG1. Valpha exhibited strong binding characteristics for its original counterparts, VEGF-A and TNF-α, but not for the extracellular matrix, resulting in a highly favorable pharmacokinetic profile in vivo. Compared with VEGF-Trap or Enbrel, both of which block either VEGF-A or TNF-α, singularly, Valpha is a highly effective molecule for reducing abnormal vascular tufts and the number of F4/80(+) macrophages in a retinopathy model. In addition, Valpha showed superior relief effects in a psoriasis model with regard to epidermal thickness and the area of blood and lymphatic vessels. Thus, the simultaneous blocking of VEGF-A and TNF-α using Valpha is an effective therapeutic strategy and cost-efficient for treatment of retinopathy and psoriasis.

Combined effects of bucillamine and etanercept on a rat type II collagen-induced arthritis model

The combined effects of bucillamine (Buc) and etanercept (ETN) on a rat model of type II collagen (CII)-induced arthritis (CIA) after treatment onset were investigated. In the combination treatment, rats received Buc 30 mg/kg orally administered once daily from the onset of arthritis or from 4 days after the onset of arthritis and ETN 0.3 mg/kg subcutaneously administered once on the day of onset. The effects of monotherapy with Buc and ETN, respectively, and of Buc + ETN combination therapy on the resulting polyarthritis were evaluated by histopathological analyses and measurements of hindpaw volumes, serum anti-collagen antibody and immunoglobulin levels, and cytokine levels. The Buc + ETN therapeutic combination reduced hindpaw swelling, synovial proliferation, bone destruction, new bone formation, and inflammatory cell infiltration in CIA. Montherapy with Buc showed a tendency to ameliorate these symptoms, while monotherapy with ETN reduced hindpaw swelling at 4 days after administration but did not maintain treatment efficacy toward the end of the experimental period. Histopathological findings did not reveal any efficacy of the ETN therapy. ETN alone increased the serum immunoglobulin levels, while its combination with Buc reduced these levels. Similar results were obtained for serum anti-CII antibody titers. The Buc + ETN combination treatment also reduced serum interleuking (IL)-1alpha and granulocyte macrophage colony-stimulating factor and tended to reduce serum IL-1beta and IL-6 levels. These results suggest that a combination therapy of Buc and ETN may be effective for the treatment of rheumatoid arthritis (RA).

Bucillamine mechanism inhibiting IL-1beta-induced VEGF production from fibroblast-like synoviocytes

We investigated the bucillamine (Buc) mechanism inhibiting interleukin (IL)-1beta-induced vascular endothelial growth factor (VEGF) production from human fibroblast-like synoviocytes (HFLS) which derived from the inflamed synovium of an RA patient using SA981, its active metabolite. HFLS did not produce IL-1beta, spontaneously. While SA981 partially inhibited IL-1beta-induced VEGF production at concentrations of 10 to 100 microM (10.1% and 14.2% inhibition of total VEGF production under IL-1beta coexistence condition, respectively), it failed to inhibit IL-1beta-induced IL-6 production at the same concentrations. IL-1beta induced phosphorylation of the mitogen-activated protein (MAP) kinases, IkappaBalpha, c-Jun and Akt. SA981 at a concentration of 100 microM partially inhibited IL-1beta-induced phosphorylation of p38MAPK and Akt (12.0% and 36.1% inhibition of each total amount of phosphoprotein under IL-1beta coexistence condition, respectively). The VEGF promoter includes four transcription factors: AP1, hypoxia-inducible factor (HIF), Sp1 and AP2 binding elements. HIF-1beta, Sp1 and AP1 increased under IL-1beta coexistence conditions. At a concentration of 100 microM, SA981 attenuated increases in HIF-1beta and Sp1 (10.1% and 19.8% inhibition of each total amount of transcription factor under IL-1beta coexistence condition, respectively), but not AP1. These results suggest that SA981 partially inhibits VEGF production via modifications on IL-1beta signaling. Attenuation of the expression of HIF-1beta and Sp1 (but not AP1) may be a key with respect to SA981's selective inhibition of VEGF production.

Therapeutic effects of the combination of methotrexate and bucillamine in early rheumatoid arthritis: a multicenter, double-blind, randomized controlled study

Disease-modifying antirheumatic drug (DMARD) combination therapies are used widely, but there have been few reports clearly demonstrating that combination therapy is more effective than DMARD monotherapy. We conducted a multicenter, double-blind controlled trial in order to clarify that the combination of methotrexate and bucillamine is more effective than either alone. The subjects of this study were 71 patients with active rheumatoid arthritis within 2 years of onset. Dosages were 8 mg methotrexate with 5 mg folic acid per week (MTX group), 200 mg bucillamine per day (BUC group), or both MTX and BUC (combination group). Clinical effects and adverse reactions were observed for 96 weeks. The ACR 20 response rate was 79.2% in the combination group, significantly higher than the rates of 43.5% for the MTX group (P = 0.008) and 45.8% for the BUC group (P = 0.0178). The cumulative survival curve of maintaining the ACR 20 response was significantly higher in the combination group than in the MTX and BUC groups (P = 0.0123 and P = 0.0088, respectively). The mean increase in the total Sharp score over 96 weeks was 12.6 +/- 9.0 in the combination group, significantly lower (P = 0.0468) than the value of 28.0 +/- 28.3 for the single DMARD (combined MTX and BUC) group. The incidence of adverse reactions did not differ significantly between the three groups. It was concluded that the combination therapy with MTX and BUC showed significantly higher clinical efficacy than either of the single DMARD therapies.

Low-dose Methotrexate Inhibits Lung Metastasis and Lengthens Survival in Rat Osteosarcoma

Lung metastasis is the most crucial event affecting the treatment of osteosarcoma and is dependent on tumor angiogenesis. To improve the prognosis for patients with osteosarcoma, prevention of lung metastasis is essential. Low-dose methotrexate is a useful drug for treating a variety of diseases. Low-dose methotrexate reportedly plays a role in antiangiogenesis for the synovial blood vessels in rheumatoid arthritis. However, whether low-dose methotrexate is correlated with tumor angiogenesis and metastasis is unclear. We investigated the inhibitory effect of methotrexate on lung metastasis in a rat osteosarcoma cell line with high metastatic potential, S-SLM. Two weeks after inoculation of S-SLM cells into male Fischer 344 rats, low-dose methotrexate (1.2 mg/kg once or twice a week) or saline was intraperitonealy injected for 4 weeks and the antimetastatic effect was evaluated. Low-dose methotrexate significantly reduced the number of lung metastatic nodules and the wet weight of the lungs. Immunohistochemical staining showed a decrease in microvessel density in the metastatic nodules. We also evaluated the effect of methotrexate on the proliferation of endothelial cells and S-SLM osteosarcoma cells in vitro. Methotrexate significantly inhibited the proliferation of endothelial cells at a lower concentration than that of S-SLM osteosarcoma cells. These data suggest that low-dose methotrexate inhibited lung metastasis of osteosarcoma through its antiangiogenic activity. Our results indicate that low-dose methotrexate is a promising drug for tumor dormancy therapy in patients with osteosarcoma and lung metastasis.

The inhibitory effect of disease-modifying anti-rheumatic drugs and steroids on gliostatin/platelet-derived endothelial cell growth factor production in human fibroblast-like synoviocytes

Gliostatin/platelet-derived endothelial cell growth factor (GLS/PD-ECGF) is known to have both angiogenic and arthritogenic activities. The purpose of this study was to investigate whether disease-modifying anti-rheumatic drugs (DMARDs) and steroids are involved in the regulation of GLS expression. Fibroblast-like synoviocytes (FLSs) obtained from patients with rheumatoid arthritis (RA) were cultured and stimulated by interleukin (IL)-1beta with or without DMARDs and steroids. The expression levels of GLS were determined using the reverse transcription-polymerase chain reaction and an ELISA. In cultured rheumatoid FLSs, the expression of GLS mRNA was significantly increased by stimulation with IL-1beta. By contrast, GLS mRNA levels in IL-1beta-stimulated FLSs were reduced by treatment with aurothioglucose (AuTG) and dexamethasone (DEX). These findings indicate that AuTG and DEX have anti-rheumatic activity, which is mediated via the suppression of GLS production. Neither methotrexate (MTX) nor sulfasalazine (SSZ) had a significant influence on GLS levels in our study.

Gene therapy targeting the Tie2 function ameliorates collagen-induced arthritis and protects against bone destruction

OBJECTIVE

In a previous study, we demonstrated that Tie2 regulates angiogenesis in arthritis. The current study was performed to determine whether systemic delivery of a soluble Tie2 receptor (ExTek) using an adenoviral vector (AdExTek) as a Tie2 inhibitor affects arthritis development and progression in an animal model.

METHODS

We used a collagen-induced arthritis (CIA) mouse model to study the outcome of treatment with either AdExTek or a control vector. The onset, incidence, and severity of arthritis were quantified. Immunohistologic analysis of endothelium obtained from the paws was performed. Bone destruction in paws was analyzed using phase-contrast radiography.

RESULTS

The data showed that systemic delivery of ExTek before disease development significantly inhibited the onset, incidence, and severity of arthritis. When AdExTek was given after disease onset, the severity of disease in mice treated with AdExTek was significantly lower than that in the control group at 35 days postimmunization, which correlated with significantly diminished angiogenesis in mouse paws. Strikingly, AdExTek treatment protected bone from erosion in the CIA model and reduced levels of RANKL. No differences in collagen-specific antibodies were detected between these 2 groups.

CONCLUSION

We demonstrated that blocking Tie2 receptor activation inhibits angiogenesis and arthritis development and protects against bone destruction in a CIA mouse model. These findings identify Tie2 as a therapeutic target for arthritis treatment and imply that interventions designed to target the Tie2 pathway could be clinically beneficial.

Effects of antirheumatic treatments on the prostaglandin E2 biosynthetic pathway

OBJECTIVE

Microsomal prostaglandin E synthase 1 (mPGES-1) is up-regulated in experimental arthritis and markedly expressed in synovial tissue biopsy samples from patients with rheumatoid arthritis (RA). This study was carried out to determine the effects of tumor necrosis factor (TNF) blockers and glucocorticoids on mPGES-1 and cyclooxygenase (COX) expression, as well as biosynthesis of PGE(2) in rheumatoid joints.

METHODS

In vitro effects of TNF blockers and dexamethasone on the PGE(2) biosynthetic pathway were examined in RA synovial fluid mononuclear cells (SFMCs) by flow cytometry. PGE(2) levels in culture supernatants were measured by enzyme immunoassay. Expression of enzymes responsible for PGE(2) synthesis ex vivo was evaluated by immunohistochemistry in synovial biopsy samples obtained from 18 patients before and after treatment with TNF blockers and from 16 patients before and after intraarticular treatment with glucocorticoids. Double immunofluorescence was performed using antibodies against mPGES-1, COX-1, COX-2, and CD163.

RESULTS

Double immunofluorescence revealed that mPGES-1 and COX-2 were colocalized in SFMCs as well as in RA synovial tissue cells. The addition of either TNF blockers or dexamethasone suppressed lipopolysaccharide-induced mPGES-1 and COX-2 expression in synovial fluid monocyte/macrophages in vitro and decreased the production of PGE(2). Intraarticular treatment with glucocorticoids significantly reduced both mPGES-1 and COX-2 expression in arthritic synovial tissue ex vivo. The number of COX-1-expressing cells in synovial tissue was also significantly decreased by glucocorticoid treatment. In contrast, neither mPGES-1 nor COX-2 expression in synovial tissue was significantly suppressed by anti-TNF therapy.

CONCLUSION

These data are the first to demonstrate the effects of antirheumatic treatments on mPGES-1 expression in RA and suggest that the inhibition of PGE(2) biosynthesis, preferably by targeting mPGES-1, might complement anti-TNF treatment for optimal antiinflammatory results in RA.

A methionine aminopeptidase-2 inhibitor, PPI-2458, for the treatment of rheumatoid arthritis

The hallmark of rheumatoid arthritis (RA) is the progressive destruction of articular joints, characterized by invasive synovial hyperplasia and pathological neovascularization. Here we report that PPI-2458, a member of the fumagillin class of irreversible methionine aminopeptidase-2 (MetAP-2) inhibitors, potently inhibits the proliferation of human fibroblast-like synoviocytes (HFLS-RA), derived from RA patients, with a growth inhibitory concentration 50 (GI(50)) of 0.04 nM and a maximum inhibition of >95% at 1 nM. Human umbilical vein endothelial cells (HUVEC) are similarly inhibited in proliferation by PPI-2458 (GI(50), 0.2 nM). We developed a method to measure the level of MetAP-2 enzyme inhibition after exposure to PPI-2458 and demonstrate that growth inhibition of PPI-2458-sensitive HFLS-RA and HUVEC is linked to MetAP-2 enzyme inhibition, in a dose-dependent fashion. The secretion of several inflammatory mediators such as IL-6 and vascular endothelial growth factor from activated HFLS-RA was not inhibited by PPI-2458. The CNS toxicity profile of PPI-2458, determined by the incidence of seizures, is significantly improved over that of the parental compound TNP-470. In the rat model of peptidoglycan-polysaccharide-induced arthritis, PPI-2458 significantly attenuated paw swelling when therapeutically administered after the onset of chronic disease. We suggest that the mechanism of PPI-2458 action, highly selective and potent anti-proliferative activity on HFLS-RA and HUVEC in vitro, a significantly improved CNS toxicity profile, and marked attenuation of chronic disease in the rat peptidoglycan-polysaccharide arthritis model in vivo, positions this compound as a drug for the treatment of RA.

Bucillamine Induces the Synthesis of Vascular Endothelial Growth Factor Dose-Dependently in Systemic Sclerosis Fibroblasts via Nuclear Factor-κB and Simian Virus 40 Promoter Factor 1 Pathways

The pathogenesis of systemic sclerosis (SSc) is characterized by activation of the immune system, impaired angiogenesis, and activated dermal fibroblasts. The effects of the immunosuppressive agent bucillamine (SA 96) on fibroblasts and angiogenic factors have not been examined. SA 96, and particularly its metabolite SA 981, increased the levels of vascular endothelial growth factor (VEGF) mRNA and protein dose-dependently in dermal fibroblasts from patients with SSc and healthy control subjects without influencing cell viability. SSc fibroblast cultures showed consistently a higher inducibility of VEGF than cultures from healthy control subjects. Preincubation with the SP-1 inhibitor mithramycin as well as blockade of nuclear factor (NF)-kappaB signaling with pyrrolidine dithiocarbamate treatment and IkappaB transfection reduced significantly the transcription of VEGF, indicating that both transcription factors contribute to the activation of VEGF by SA 981. Specific binding of NF-kappaB protein to its binding site after treatment with SA 981 was confirmed by electrophoretic mobility shift assay. In contrast, SA 981 did not influence the stability of VEGF mRNA as analyzed with actinomycin D assays. The study provides evidence for a role of NF-kappaB in the transcriptional regulation of the VEGF gene. SA 96 might have positive aspects on the impaired angiogenesis in patients with SSc.

Inhibitory effects of bucillamine on the expression of vascular cell adhesion molecule-1 in human umbilical vein endothelial cells

Bucillamine (BUC) has been found to have beneficial effects in the treatment of rheumatoid arthritis (RA), in which the activation of endothelial cells plays an important role in the pathogenesis. The current studies examined the effect of BUC and its intramolecular disulfide form (BUC-ID) on the expression of adhesion molecules in human umbilical vein endothelial cells (HUVEC) stimulated with tumor necrosis factor-alpha (TNF-alpha). HUVEC (4 x 10(4)/well) were incubated with medium M199 containing heparin and 20% FCS with endothelial cell growth supplement (ECGS) for 24 h in the presence or absence of BUC or BUC-ID, after which the culture medium was replaced with ECGS free medium. Then the cultures were further carried out for additional 24 h with TNF-alpha (10 ng/ml) in the presence or absence of BUC or BUC-ID. BUC-ID, but not BUC, appeared to suppress the expression of VCAM-1 on HUVEC stimulated with TNF-alpha in a dose-response manner at its pharmacologically relevant concentrations (0.3-3.0 microg/ml), whereas only the 3 microg/ml concentration level of BUC-ID had a statistically significant effect, although the effect was relatively small. By contrast, lower concentrations of BUC-ID (1-3 microg/ml) suppressed the secretion of soluble VCAM-1 by HUVEC much more effectively. Of note, at the concentration of 3 microg/ml neither BUC nor BUC-ID significantly influenced the expression of ICAM-1 and E-selectin on TNF-alpha stimulated HUVEC. These results indicate that BUC-ID, but not BUC, specifically downregulates the surface expression of VCAM-1 as well as the release of soluble VCAM-1 by HUVEC stimulated with TNF-alpha. BUC-ID suppressed the production of solubleVCAM-1 by RA bone marrow CD34+ cells stimulated with SCF, GM-CSF and TNF-alpha more effectively than BUC. The data thus suggest that one of the mechanisms of action of BUC involves the inhibition of the activation of endothelial cells.

Lack of evidence for inhibition of angiogenesis as a central mechanism of the antiarthritic effect of methotrexate

OBJECTIVES

The aim of this study was to investigate whether methotrexate (MTX) has an antiangiogenic effect and whether this property plays a role in the control of rheumatoid arthritis (RA).

METHODS

A human placenta angiogenesis assay was used to examine the antiangiogenic effects of MTX in vitro. In addition, DBA/1 mice were used to compare the antiarthritic effect of MTX in collagen-induced arthritis (CIA) and its antiangiogenic effect in a murine in vivo matrigel model for angiogenesis.

RESULTS

The spreading of microvessels from placental vessel fragments was not significantly inhibited by MTX. Treatment with MTX reduced significantly the incidence of CIA in DBA/1 mice in a dose-dependent manner. However, treatment with the same doses of MTX did not significantly reduce vessel growth in subcutaneous depots of bFGF-enriched matrigel.

CONCLUSION

These data support the hypothesis that inhibition of angiogenesis does not significantly contribute to the antiarthritic effect of MTX seen in patients and animal models for RA. Therefore, the combination of MTX with antiangiogenic drugs appears to be a rational strategy in the treatment of RA.

Blockade of Vascular Endothelial Growth Factor Receptor I (VEGF-RI), but not VEGF-RII, Suppresses Joint Destruction in the K/BxN Model of Rheumatoid Arthritis

It was recently shown that vascular endothelial growth factor (VEGF), a growth factor for endothelial cells, plays a pivotal role in rheumatoid arthritis. VEGF binds to specific receptors, known as VEGF-RI and VEGF-RII. We assessed the physical and histological effects of selective blockade of VEGF and its receptors in transgenic K/BxN mice, a model of rheumatoid arthritis very close to the human disease. Mice were treated with anti-mouse VEGF Ab, anti-mouse VEGF-RI and -RII Abs, and an inhibitor of VEGF-RI tyrosine kinase. Disease activity was monitored using clinical indexes and by histological examination. We found that synovial cells from arthritic joints express VEGF, VEGF-RI, and VEGF-RII. Treatment with anti-VEGF-RI strongly attenuated the disease throughout the study period, while anti-VEGF only transiently delayed disease onset. Treatment with anti-VEGF-RII had no effect. Anti-VEGF-RI reduced the intensity of clinical manifestations and, based on qualitative and semiquantitative histological analyses, prevented joint damage. Treatment with a VEGF-RI tyrosine kinase inhibitor almost abolished the disease. These results show that VEGF is a key factor in pannus development, acting through the VEGF-RI pathway. The observation that in vivo administration of specific inhibitors targeting the VEGF-RI pathway suppressed arthritis and prevented bone destruction opens up new possibilities for the treatment of rheumatoid arthritis.

Recent data on the role for angiogenesis in rheumatoid arthritis

Angiogenesis is central to the development and perpetuation of rheumatoid synovitis. Vascular endothelial growth factor (VEGF), the main mediator of angiogenesis, is found in the synovial fluid and serum of patients with rheumatoid arthritis (RA), and its expression is correlated with disease severity. Compelling evidence that VEGF is involved in synovitis has been obtained from experimental models of RA. In particular, VEGF inhibition by synthetic compounds (e.g. TNP-470) or by naturally occurring factors (e.g., the soluble VEGF receptor) produce therapeutic effects. Angiopoietin-1, a recently discovered growth factor specific for neovascularization, is expressed within the rheumatoid synovium and may be stimulated by TNF-alpha. Other compounds, including integrins, fibroblast growth factor, and proinflammatory cytokines contribute to joint angiogenesis and, therefore, to the development of rheumatoid synovitis. Assessing vascularity may prove useful for evaluating or even predicting bone destruction. Furthermore, inhibition of angiogenesis may prove useful as an adjunct to current anti-inflammatory treatments.

The therapeutic potential of TNF-alpha blockade in rheumatoid arthritis

Rheumatoid arthritis is a chronic autoimmune disease characterised by inflammation of the synovial lining of joints and destruction of cartilage and bone. Many pro-inflammatory cytokines, chemokines and growth factors are expressed in diseased joints, and recognition of the key role of TNF-alpha led to the development of highly effective new therapies. TNF-alpha inhibitors, such as monoclonal anti-TNF-alpha antibody infliximab (Remicade), have demonstrated efficacy in clinical trials. It is now clear that TNF-alpha blockade, in addition to reducing joint inflammation and leukocyte infiltration, also results in decreased formation of new blood vessels in the synovium. Such mechanism of action studies are now paving the way for the development of the next generation of drugs for treatment of rheumatoid arthritis.

Does vascular endothelial growth factor in the rheumatoid synovium predict joint destruction? A clinical, radiological, and pathological study in 12 patients monitored for 10 years

OBJECTIVE

Synovial angiogenesis is at the epicenter of rheumatoid pannus development and is largely dependent on vascular endothelial growth factor (VEGF). We sought to determine whether the VEGF level in rheumatoid synovial tissue is a marker for disease severity.

PATIENTS AND METHODS

Twelve patients with rheumatoid arthritis (RA) underwent a clinical and radiological evaluation at the time of a synovial biopsy done during joint surgery required by RA progression (T1) and, on average, 10 years later (T2). Immunohistochemistry was used to detect and quantitate VEGF in the synovial biopsy taken at T1.

RESULTS

VEGF labeling was seen on endothelial cells and macrophages in all 12 synovial biopsies. The amount of endothelial-cell VEGF labeling (assessed semi-quantitatively) was significantly correlated with Larsen score progression during the 10-year follow-up. The amounts of endothelial cell or macrophage VEGF labeling was not correlated with the joint count, radiological stage of the biopsied joint or progression of this stage, Larsen scores at T1 or T2, presence of rheumatoid factor, or presence of extra-articular manifestations.

CONCLUSION

Our results suggest that the amount of VEGF in the rheumatoid synovium may be a marker for joint destruction in patients with RA.

The angiogenic pathway "vascular endothelial growth factor/flk-1(KDR)-receptor" in rheumatoid arthritis and osteoarthritis

Active angiogenesis, together with an up-regulation of angiogenic factors, is evident in the synovium of both rheumatoid arthritis (RA) and osteoarthritis (OA). The present study assessed, by immunohistochemistry, the microvessel density in the synovium of these arthritides and in normal controls, in relation to the expression of the angiogenic factors vascular endothelial growth factor (VEGF) and platelet-derived endothelial cell growth factor (PD-ECGF) and the apoptosis-related proteins bcl-2 and p53. More importantly, using the novel 11B5 MAb, the activated "VEGF/flk-1(KDR)-receptor" microvessel density was assessed. VEGF expression in fibroblasts was diffuse in both RA and OA. Diffuse PD-ECGF expression of fibroblasts was noted in all cases of RA, while fibroblast reactivity was focal in the OA material. The standard microvessel density (sMVD), as assessed with the anti-CD31 monoclonal antibody (MAb), was higher in RA (64+/-12) and in OA (65+/-16) than in normal tissues (52+/-8; p=0.008 and 0.0004, respectively). The activated microvessel density (aMVD), assessed with the 11B5 MAb, was significantly higher in RA (29+/-10) than in OA (17+/-4; p<0.0001) and than in normal tissues (14+/-2; p<0.0001). The "activation ratio" (aMVD/sMVD) was statistically higher in RA (0.46+/-0.17) than in OA and normal synovial tissues, the latter two having a similar ratio (0.28+/-0.08 and 0.26+/-0.03, respectively). Cytoplasmic bcl-2 expression was frequent in the synovial cells of OA, but rare in RA. Nuclear p53 protein accumulation was never observed. It is suggested that the angiogenic pathway VEGF/flk-1(KDR) may play an important role in the pathogenesis of RA and OA. Thus, failure of VEGF/flk-1(KDR) activation, in the presence of increased VEGF expression, may indicate a synovium with an impaired capacity to establish a viable vasculature, consistent with the degenerative nature of OA. On the other hand, the activated angiogenesis in RA shows a functional, still pathologically up-regulated VEGF/flk-1(KDR) pathway. Whether restoration of an impaired VEGF/flk-1(KDR) pathway in OA, or inhibition of this in RA, would prove of therapeutic importance requires further investigation.

Effects of combinations of anti-rheumatic drugs on the production of vascular endothelial growth factor and basic fibroblast growth factor in cultured synoviocytes and patients with rheumatoid arthritis

OBJECTIVE

To examine whether different combinations of disease-modifying anti-rheumatic drugs (DMARDs), including bucillamine (BUC), gold sodium thiomalate (GST), methotrexate (MTX), salazosulphapyridine (SASP) and dexamethasone (DEX; a steroid), act by inhibiting the production of vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF) in cultured synoviocytes, causing a decrease in their serum concentrations in patients with rheumatoid arthritis (RA).

METHODS

The VEGF and bFGF concentrations in cultured synoviocytes and peripheral blood from patients with RA were measured by enzyme-linked immunosorbent assay and their serum concentrations were measured at two time points.

RESULTS

BUC and GST inhibited VEGF production even when given alone, and a combination of BUC, GST and MTX with DEX also inhibited VEGF production. None of the DMARDs or DEX inhibited bFGF production when given alone, but a combination of SASP and GST inhibited the production of bFGF in cultured synoviocytes. Serum VEGF concentrations were significantly decreased 6 months after the commencement of medication compared with their concentrations before medication.

CONCLUSION

Our results show that the effects of a combination of DEX with any two of BUC, GST, SASP and MTX on the production of VEGF and bFGF in cultured synoviocytes and on the serum concentrations of VEGF in patients with RA may be based on synergistic or additive effects of the drugs.

Vascular endothelial growth factor production in polymyalgia rheumatica

OBJECTIVE

To evaluate peripheral production and synovial expression of vascular endothelial growth factor (VEGF) in polymyalgia rheumatica (PMR).

METHODS

Circulating levels of VEGF in PMR (serum concentration and in vitro release by peripheral blood mononuclear cells [PBMC]) were investigated by enzyme-linked immunosorbent assay. Local expression of VEGF in shoulder synovial tissue was investigated by immunohistochemical analysis. Investigations were performed in patients with active, untreated disease and in patients treated with corticosteroids.

RESULTS

VEGF serum concentrations were significantly higher in untreated PMR patients than in normal control subjects. During steroid treatment, VEGF serum concentrations reached their lowest level after the sixth month of treatment. PBMC isolated from untreated PMR patients spontaneously secreted a higher amount of VEGF compared with PBMC from control subjects. Corticosteroid therapy did not affect the ability of PBMC to produce VEGF. Immunohistochemical staining performed on shoulder synovial tissue showed VEGF expression in both the lining layer and the sublining area. In 3 of 4 treated patients, no VEGF staining was found in synovial tissue during corticosteroid therapy. VEGF expression correlated with vessel density, but was not associated with alphavbeta3 and alphavbeta5 integrin expression.

CONCLUSION

Peripheral and local VEGF releases have different responses to steroid treatment in PMR. The lack of response to corticosteroids by peripheral VEGF production supports the hypothesis that systemic involvement is dominant in PMR. At the synovial level, VEGF production is linked to vascular proliferation and is thus directly involved in the pathogenesis of synovitis.

Angiogenesis in inflammatory joint disease: a target for therapeutic intervention

The evidence reviewed here clearly supports the concept that pathological angiogenesis is an important component in inflammatory joint erosion. Of the primary angiogenic factors, VEGF-A is clearly a key participant in this mechanism and a range of anti-VEGF strategies is being developed to neutralize its biological function [54,55]. Currently available drugs are also being screened for VEGF antagonistic effects. In a study of the effects of existing disease-modifying anti-rheumatic drugs on cultured synovial cells, bucillamine and dexamethasone showed significant inhibition of VEGF production [56]. In addition, COX-1 and COX-2 non-steroidal anti-inflammatory drugs have been shown to inhibit angiogenesis by blocking VEGF-induced signal transduction [57]. Modulation of the immune network in RA using TNF-α antagonists is producing promising results, but as outlined in this review, this treatment on its own is unlikely to control joint angiogenesis. It is possible that combination therapy, e.g. TNF-α antagonist and a VEGF signal transduction inhibitor, will be more effective by using antagonists that block different but key control points in the disease pathology.

Treatment with soluble VEGF receptor reduces disease severity in murine collagen-induced arthritis

Maintenance of the invasive pannus in rheumatoid arthritis is an integral part of disease progression. The synovial vasculature plays an important role in the delivery of nutrients, oxygen, and inflammatory cells to the synovium. Vascular endothelial growth factor (VEGF), an endothelial mitogen expressed by cells within the synovial membrane, is thought to contribute to the formation of synovial blood vessels. Our objective in this study was to measure the kinetics of VEGF production in a murine model of collagen-induced arthritis and to determine whether VEGF blockade reduces disease progression. Synovial cells isolated from the knee joints of naive or sham-immunized mice, or from mice immunized with collagen but without arthritis, released little or no detectable VEGF. Onset of arthritis was associated with expression of VEGF mRNA and protein. The levels of VEGF secreted by synovial cells isolated from the joints of mice with severe arthritis were significantly higher than from mice with mild disease. To block VEGF activity, animals were treated after arthritis onset with a soluble form of the Flt-1 VEGF receptor (sFlt), which was polyethylene glycol (PEG)-linked to increase its in vivo half-life. Treatment of arthritic mice with sFlt-PEG significantly reduced both clinical score and paw swelling, compared with untreated or control-treated (heat-denatured sFlt-PEG) animals. There was also significantly less joint inflammation and reduced bone and cartilage destruction in sFlt-PEG-treated animals, as assessed by histology. Our data demonstrate that, in collagen-induced arthritis, expression of the potent angiogenic cytokine VEGF correlates with disease severity. Furthermore, specific blockade of VEGF activity results in attenuation of arthritis in both macroscopic and microscopic parameters. These observations indicate that blood vessel formation is integral to the development of arthritis and that blockade of VEGF activity might be of therapeutic benefit in rheumatoid arthritis.

Activation of synoviocytes

The evaluation of molecular pathways has revealed various novel insights into rheumatoid arthritis pathophysiology during the past year. In addition, there is an increasing tendency toward analysis not merely of a single mechanism but rather of data addressing a substantial part of the cascade of events leading to cellular activation. Because synovial fibroblasts are key cells involved in joint destruction, this review outlines the events that trigger or inhibit the crucial pathways leading to their aggressive behavior. Major topics include cellular and humoral interactions (frequently modulated by cytokines), intracellular signaling and upregulation of gene transcription, and the deleterious effects on articular homeostasis.