Modulation of angiogenic vascular endothelial growth factor by tumor necrosis factor alpha and interleukin-1 in rheumatoid arthritis

Oxidation in rheumatoid arthritis

Oxygen metabolism has an important role in the pathogenesis of rheumatoid arthritis. Reactive oxygen species (ROS) produced in the course of cellular oxidative phosphorylation, and by activated phagocytic cells during oxidative bursts, exceed the physiological buffering capacity and result in oxidative stress. The excessive production of ROS can damage protein, lipids, nucleic acids, and matrix components. They also serve as important intracellular signaling molecules that amplify the synovial inflammatory-proliferative response. Repetitive cycles of hypoxia and reoxygenation associated with changes in synovial perfusion are postulated to activate hypoxia-inducible factor-1alpha and nuclear factor-kappaB, two key transcription factors that are regulated by changes in cellular oxygenation and cytokine stimulation, and that in turn orchestrate the expression of a spectrum of genes critical to the persistence of synovitis. An understanding of the complex interactions involved in these pathways might allow the development of novel therapeutic strategies for rheumatoid arthritis.

Efficacy of infliximab for disc herniation-induced sciatica: one-year follow-up

STUDY DESIGN

An open-label trial.

OBJECTIVES

To test the long-term efficacy of infliximab, a monoclonal antibody against tumor necrosis factor-alpha (TNF-alpha), in disc herniation-induced sciatica.

SUMMARY OF BACKGROUND DATA

Our recent trial indicated that a single infusion of 3 mg/weight-kg of infliximab produced a rapid curative effect in disc herniation-induced sciatica. Here, we describe the 1-year effect of a 3 mg/kg of infliximab in these 10 patients and our experience with a lower dose of 1 mg/kg of infliximab for the same indication in 2 additional patients.

METHODS

Patients with severe sciatica were treated with a single infusion of infliximab, 3 mg/weight-kg in 10 patients and 1 mg/kg in 2 patients, intravenously over 2 hours. The outcomes (leg and back pain on a 100-mm visual scale, Oswestry disability, clinical signs) were assessed at 1 week, 2 weeks, 1 month, 3 months, 6 months, and 1 year after the infusion. The outcomes with 3 mg/kg of infliximab were compared to 62 patients who received periradicular saline for sciatica in a previous trial. The resorption rate of disc herniations from baseline to 1 year was compared between infliximab and control groups.

RESULTS

The response to 1 mg/kg of infliximab for leg pain was good only in 1 of the 2 patients treated, whereas the response to 3 mg/kg of infliximab for leg pain was sustained in most patients over the 1-year follow-up. The 1-year response significantly favored 3 mg/kg of infliximab over periradicular saline in leg pain (P = 0.005) and disability (P = 0.003). Neurologic abnormalities normalized more comprehensively in the infliximab group (P = 0.001). Reduction in disc herniation volume did not differ between the infliximab-treated patients and controls.

CONCLUSIONS

The results showed that the beneficial effect of a single infusion of 3 mg/kg of infliximab for herniation-induced sciatica is sustained in most patients over a 1-year follow-up period. Furthermore, infliximab does not seem to interfere with the spontaneous resorption of disc herniations.

IL-17, IL-1beta and TNF-alpha stimulate VEGF production by dedifferentiated chondrocytes

OBJECTIVE

To verify the involvement of proinflammatory cytokines IL-17, IL-1beta and tumor necrosis factor alpha (TNF-alpha) in cartilage vascularization by stimulating the production of vascular endothelial growth factor (VEGF) by chondrocytes isolated from patients with osteoarthritis (OA), in comparison with patients with rheumatoid arthritis (RA) and patients with femoral or humeral neck fracture (FP).

DESIGN

Chondrocytes isolated from patients with OA were maintained in monolayer culture for several passages. Chondrocyte dedifferentiation was monitored by the synthesis of cathepsin B by these cells. Chondrocytes freshly isolated at each subculture (subcultures 1-3) were stimulated with IL-17, IL-1beta or TNF-alpha. Supernatants were collected, immunoassayed for the production of VEGF and cathepsin B and assayed as the source of VEGF on the VEGF sensible ECV304 cell line. The cells were used to quantify intracellular cathepsin B enzymatic activity.

RESULTS

In differentiated conditions IL-1beta and TNF-alpha, but not IL-17, can inhibit the spontaneous secretion of VEGF by human OA, RA and FP chondrocytes, and IL-17 can restore the decrease in VEGF secretion caused by TNF-alpha. IL-17, together with IL-1beta and TNF-alpha, can enhance VEGF secretion to various extents by dedifferentiated OA chondrocytes. This change in effect with respect to primary culture was observable for all cytokines at the beginning of dedifferentiation, when the production of VEGF by chondrocytes had dramatically fallen and the cathepsin B synthesis had increased. The amount of VEGF induced by cytokines on dedifferentiated chondrocytes never reached the amount of VEGF produced by differentiated chondrocytes. VEGF produced by chondrocytes stimulated the ECV304 cell line proliferation.

CONCLUSIONS

These results indicate that dedifferentiated OA chondrocytes secrete VEGF after stimulation with proinflammatory cytokines. This event may be responsible for neovascularization found in OA cartilage.

Infliximab treatment of rheumatoid arthritis

Infliximab was the first anti-TNF agent used to treat rheumatoid arthritis to provide proof of concept of the role of TNF-alpha in this condition. It has become widely used since, principally as an effective treatment in combination with methotrexate, but also as monotherapy for the treatment of Crohn's disease, ankylosing spondylitis,and psoriatic arthritis. The benefits of infliximab in controlling signs and symptoms, improving quality of life, preventing structural joint damage, and possible healing of bone provide an important option for the treatment of rheumatoid arthritis.

Dual functional roles of Tie-2/angiopoietin in TNF-alpha-mediated angiogenesis

Inflammation and angiogenesis are associated with pathological disorders. TNF-alpha is a major inflammatory cytokine that also regulates angiogenesis. TNF-alpha has been shown to regulate Tie-2 and angiopoietin (Ang) expression, but the functional significance is less clear. In this study, we showed that TNF-alpha induced a weak angiogenic response in a mouse cornea assay. Systemic overexpression of Ang-1 or Ang-2 dramatically increased corneal angiogenesis induced by TNF-alpha. In the absence of TNF-alpha, neither Ang-1 nor Ang-2 promoted corneal angiogenesis. Low doses (0-25 ng/ml) of TNF-alpha increased vascular branch formation of cultured endothelial cells. Overexpression of Ang-1 or Ang-2 enhanced the effects of TNF-alpha. These data suggest that Tie-2 signaling synergistically amplifies and participates in TNF-alpha-mediated angiogenesis. In addition, high doses (>/=50 ng/ml) of TNF-alpha induced apoptosis in endothelial cells, but addition of Ang-1 or Ang-2 significantly reduced cell death. Enhanced endothelial cell survival was correlated with Akt phosphorylation. Collectively, our data reveal dual functional roles of Tie-2: low doses enhance TNF-alpha-induced angiogenesis, and high doses attenuate TNF-alpha-induced cell death. The study provides evidence supporting a role for Tie-2 in inflammatory angiogenesis.

Cytokine and chemokine receptor profile of peripheral blood mononuclear cells during treatment with infliximab in patients with active rheumatoid arthritis

OBJECTIVES

To analyse immunological changes during treatment with a monoclonal anti-tumour necrosis factor alpha (TNFalpha) antibody, infliximab, in patients with rheumatoid arthritis (RA).

METHODS

25 patients with RA and 5 patients with other arthritides were studied during the first 6 weeks of treatment with infliximab. At the start of treatment and after 2 and 6 weeks, spontaneous expression of CCR3 and CCR5 on peripheral blood T cells and monocytes was studied by flow cytometry. The secretion and mRNA expression of interferon gamma (IFNgamma), interleukin (IL)4, IL5, and TNFalpha from phytohaemagglutinin (PHA) stimulated peripheral blood mononuclear cells was measured with an ELISA and RT-PCR. Plasma levels of C reactive protein, serum amyloid protein A, rheumatoid factor, and antibodies to filaggrin and citrullinated cyclic peptide were measured with an ELISA.

RESULTS

The number of CD4 T cells and CD14 monocytes expressing CCR3 (p = 0.013, p = 0.009, respectively) and CD8 T cells expressing CCR5 (p = 0.040) as well as PHA stimulated secretion of IL4 and IFNgamma (p<0.05) increased during treatment in patients with RA. 15 (60%) patients with RA achieved clinical response (at least ACR20) during the first 2 weeks. The number of T cells expressing CCR3 and CCR5 was higher before treatment in non-responders than in responders (p<0.05). The number of T cells increased in responders.

CONCLUSION

Increase in secretion of Th1 and Th2 cytokines together with induced expression of chemokine receptors on T cells and monocytes suggest restoration of peripheral cell mediated immunity and blockade of the accumulation of inflammatory cells in joints as response to treatment.

Role of RUNX in autoimmune diseases linking rheumatoid arthritis, psoriasis and lupus

Recent studies investigating the genetic susceptibility of systemic lupus erythematosus, rheumatoid arthritis and psoriasis have revealed a potential role for the RUNX proteins in the development of autoimmune disease. A new pathway of disease pathogenesis opens new avenues of research with thousands of questions that remain to be answered. In this review I attempt to propose how the RUNX proteins might be involved in these diseases and review current knowledge on this very interesting trio of transcription factors that was previously only suspected to be involved in cancer.

Comparison of ultrasonographic assessment of synovitis and joint vascularity with radiographic evaluation in a randomized, placebo-controlled study of infliximab therapy in early rheumatoid arthritis

OBJECTIVE

To investigate sensitive ultrasonographic imaging methods for detection of synovial thickness and vascularity to discriminate between patients with early rheumatoid arthritis (RA) receiving infliximab + methotrexate (MTX) versus placebo + MTX over 18 weeks, and to compare the relationship between synovial thickening and vascularity at baseline and radiologic damage to joints of the hands and feet at 54 weeks.

METHODS

Patients with early RA (duration <3 years) receiving stable dosages of MTX were randomly assigned to receive blinded infusions of 5 mg/kg infliximab (n = 12) or placebo (n = 12) at weeks 0, 2, 6, and then every 8 weeks until week 46. At baseline and week 18, clinical assessments were performed, and metacarpophalangeal joints were assessed by high-frequency ultrasonography and power Doppler ultrasonography measurements. Radiographs of the hands and feet taken at baseline and at 54 weeks were evaluated using the van der Heijde modification of the Sharp method (vdH-Sharp score).

RESULTS

Using changes in the total vdH-Sharp score over 54 weeks and changes in synovial thickening and joint vascularity at 18 weeks, we were able to distinguish those patients receiving infusions of infliximab + MTX from those receiving placebo + MTX. Sonographic measurements of synovial thickening and vascularity at baseline in the placebo + MTX group demonstrated clear relationships with the magnitude of radiologic joint damage at week 54. Infliximab + MTX treatment abolished these relationships.

CONCLUSION

The delay or reversal of inflammatory and joint-destructive mechanisms in patients with early RA was already apparent following 18 weeks of treatment with infliximab + MTX and was reflected in radiologic changes at 54 weeks.

Historical review: Cytokines as therapeutics and targets of therapeutics

Cytokine research has spawned the introduction of new therapies that have revolutionized the treatment of many important diseases. These therapeutic advances have resulted from two very different strategies. The first therapeutic strategy embodies the administration of purified, recombinant cytokines. The second relies on the administration of therapeutics that inhibit the harmful effects of upregulated, endogenous cytokines. Examples of successful cytokine therapeutics include hematopoietic growth factors (colony stimulating factors) and interferons. Prime examples of cytokine antagonists that have profoundly altered the treatment of some inflammatory disorders are agents that inhibit the effects of tumor necrosis factor (TNF). In this article, we highlight some of the studies that have been responsible for the introduction of cytokine and anti-cytokine therapies, with emphasis on the development of interferons and anti-TNF agents.

TNF autovaccination induces self anti-TNF antibodies and inhibits metastasis in a murine melanoma model

TNF is a proinflammatory cytokine involved in the pathogenesis of chronic inflammatory diseases, but also in metastasis in certain types of cancer. In terms of therapy, TNF is targeted by anti-TNF neutralising monoclonal antibodies or soluble TNF receptors. Recently, a novel strategy based on the generation of self anti-TNF antibodies (TNF autovaccination) has been developed. We have previously shown that TNF autovaccination successfully generates high anti-TNF antibody titres, blocks TNF and ameliorates collagen-induced arthritis in DBA/1 mice. In this study, we examined the ability of TNF autovaccination to generate anti-TNF antibody titres and block metastasis in the murine B16F10 melanoma model. We found that immunisation of C57BL/6 mice with TNF autovaccine produces a 100-fold antibody response to TNF compared to immunisation with phosphate-buffered saline vehicle control and significantly reduces both the number (P<0.01) and size of metastases (P<0.01) of B16F10 melanoma cells. This effect is also observed when an anti-TNF neutralising monoclonal antibody is administered, confirming the essential role TNF plays in metastasis in this model. This study suggests that TNF autovaccination is a cheaper and highly efficient alternative that can block TNF and reduce metastasis in vivo and trials with TNF autovaccination are already underway in patients with metastatic cancer.

Interactions between bradykinin (BK) and cell adhesion molecule (CAM) expression in peptidoglycan‐polysaccharide (PG‐PS)‐induced arthritis

Bradykinin (BK), a vasoactive, proinflammatory nonapeptide, promotes cell adhesion molecule (CAM) expression, leukocyte sequestration, inter-endothelial gap formation, and protein extravasation in postcapillary venules. These effects are mediated by bradykinin-1 (B1R) and-2 (B2R) receptors. We delineated some of the mechanisms by which BK could influence chronic inflammation by altering CAM expression on leukocytes, endothelium, and synovium in joint sections of peptidoglycan-polysaccharide-injected Lewis rats. Blocking B1R results in significantly increased joint inflammation. Immunohistochemistry of the B1R antagonist group revealed increased leukocyte and synovial CD11b and CD54 expression and increased CD11b and CD44 endothelial expression. B2R antagonism decreased leukocyte and synovial CD44 and CD54 and endothelial CD11b expression. Although these findings implicate B2R involvement in the acute phase of inflammation by facilitating leukocyte activation (CD11b), homing (CD44), and transmigration (CD54). Treatment with a B2R antagonist did not affect the disease evolution in this model. In contrast, when both BK receptors are blocked, the aggravation of inflammation by B1R blockade is neutralized and there is no difference from the disease-untreated model. Our findings suggest that B1R and B2R signaling show physiologic antagonism. B1R signaling suggests involvement in down-regulation of leukocyte activation, transmigration, and homing. Further studies are needed to evaluate the B1 receptor agonist's role in this model.

The transfer of a laboratory based hypothesis to a clinically useful therapy: the development of anti-TNF therapy of rheumatoid arthritis

The development of anti-TNF therapy is a key step forward in rheumatology as it is the first new therapy for based on investigating the molecular mechanisms of this disease. This chapter reviews how this discovery was made.

ESE-1 is a novel transcriptional mediator of angiopoietin-1 expression in the setting of inflammation

Angiogenesis is a critical component of the inflammatory response associated with a number of conditions. Angiopoietin-1 (Ang-1) is an angiogenic growth factor that promotes the chemotaxis of endothelial cells and facilitates the maturation of new blood vessels. Ang-1 expression is up-regulated in response to tumor necrosis factor-alpha (TNF-alpha). To begin to elucidate the underlying molecular mechanisms by which Ang-1 gene expression is regulated during inflammation, we isolated 3.2 kb of the Ang-1 promoter that contain regulatory elements sufficient to mediate induction of the promoter in response to TNF-alpha, interleukin-1beta, and endotoxin. Surprisingly, sequence analysis of this promoter failed to reveal binding sites for transcription factors that are frequently associated with mediating inflammatory responses, such as NF-kappaB, STAT, NFAT, or C/EBP. However, putative binding sites for ETS and AP-1 transcription factor family members were identified. Interestingly, among a panel of ETS factors tested in a transient transfection assay, only the ETS factor ESE-1 was capable of transactivating the Ang-1 promoter. ESE-1 binds to specific ETS sites within the Ang-1 promoter that are functionally important for transactivation by ESE-1. ESE-1 and Ang-1 are induced in synovial fibroblasts in response to inflammatory cytokines, with ESE-1 induction slightly preceding that of Ang-1. Mutation of a high-affinity ESE-1 binding site leads to a marked reduction in Ang-1 transactivation by ESE-1, inducibility by inflammatory cytokines, and DNA binding to the ESE-1 protein. Transcriptional profiling of cells transiently transfected with an ESE-1 expression vector demonstrates that the endogenous Ang-1 gene is directly inducible by ESE-1. Finally, Ang-1 and ESE-1 exhibit a similar and strong expression pattern in the synovium of patients with rheumatoid arthritis. Our results support a novel paradigm for the ETS factor ESE-1 as a transcriptional mediator of angiogenesis in the setting of inflammation.

Antiangiogenesis: the fifth cancer treatment modality?

PURPOSE/OBJECTIVES

To describe the biologic process of angiogenesis and the potential role of antiangiogenesis therapy in cancer treatment.

DATA SOURCES

Published articles, conference proceedings, and computerized databases.

DATA SYNTHESIS

Angiogenesis is the development of blood vessels. Antiangiogenic agents prevent the development of blood vessels, therefore preventing one mode of cancer metastasis. Clinical trials must be conducted to ascertain the most powerful antiangiogenic therapies. Trials combine chemotherapy, biotherapy, and radiotherapy with antiangiogenic therapy.

CONCLUSIONS

Information from animal studies has revealed that antiangiogenesis is a viable option in treating cancer and preventing metastasis. Although human studies are rare, preliminary results are promising, especially when antiangiogenesis is used in combination with current cancer treatment modalities.

IMPLICATIONS FOR NURSING

Nurses are in a unique position to teach patients about new treatments for cancer. Nurses must be knowledgeable about angiogenesis and the availability of potential antiangiogenesis agents. Nurses will be vital in collecting data in clinical trials, considering the subjective data that will be obtained.

From the cradle to the clinic: VEGF in developmental, physiological, and pathological angiogenesis

Formation of new blood vessels, which is fundamental in embryonic development, occurs through a combination of angiogenesis and vasculogenesis. Angiogenesis also plays a vital role postnatally, especially in reparative processes such as wound and fracture healing. Some of these events, especially in fracture healing, recapitulate processes observed in developmental angiogenesis. However, dysregulated angiogenesis is well documented to underlie a number of pathological disorders, including rheumatoid arthritis (RA). The vascular endothelial growth factor (VEGF)/VEGF receptor system is the best characterized regulator of angiogenesis. VEGF is expressed in a range of cells in response to soluble mediators (such as cytokines and growth factors), cell-bound stimuli (such as CD40 ligand), and environmental factors (such as hypoxia). As a consequence, this molecule is vital in the modulation of physiological and pathological angiogenesis. This review will focus in particular on the role played by VEGF in embryogenesis and skeletal growth, in fracture healing (in which increased angiogenesis is likely to be beneficial in promoting union), and in RA (in which excessive angiogenesis is thought to play a significant role in disease pathogenesis). In the not-too-distant future, targeting VEGF may prove to be of benefit in the treatment of diseases associated with excessive or aberrant angiogenesis, such as malignancies and RA.

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.

Adenoviral delivery of soluble VEGF receptor 1 (sFlt-1) abrogates disease activity in murine collagen-induced arthritis

The angiogenic factor VEGF promotes synovitis and bone erosion in rheumatoid arthritis (RA). Previously, we have demonstrated that VEGF expression correlates with disease severity in RA patients and in murine collagen-induced arthritis (CIA). In this study, we adopted an adenoviral gene delivery system expressing soluble VEGF receptor 1 (sFlt-1) to further study the role of VEGF in CIA. Arthritis was induced in DBA/1 mice by injection of bovine collagen. Adenoviruses expressing human soluble VEGF receptor 1 (AdvsFlt-1), or without transgene (Adv0), were injected intravenously on the first day of arthritis. We found that disease severity and paw swelling were significantly suppressed in mice receiving AdvsFlt-1, when compared to untreated or Adv0-treated mice. Expression of sFlt-1 peaked 24 h after injection, with protein detectable in the liver, synovial issue and serum, but rapidly decreased by 72 h. The effect of sFlt-1 expression on signs of disease was paralleled by reduced joint destruction and decreased expression of the vascular marker von Willebrand factor. In summary, adenoviral delivery of human soluble VEGF receptor type 1 significantly suppressed disease activity in CIA. The actions of AdvsFlt-1 are likely to be mediated by reduced synovial neovascularization, and these results support the concept that VEGF blockade may be an effective therapeutic adjunct for the treatment of RA.

Marked increase in vascular endothelial growth factor concentrations during Escherichia coli endotoxin-induced acute inflammation in humans

BACKGROUND

Bacterial endotoxins can induce the synthesis and release of vascular endothelial growth factor (VEGF), which may alter vascular permeability and cause vascular leakage.

MATERIALS AND METHODS

The effect of acute systemic inflammation on VEGF concentration was measured in healthy males after an intravenous bolus infusion of Escherichia coli endotoxin (lipopolysaccharide, LPS, 20 IU kg-1) in a double-blind, placebo-controlled parallel group study. LPS administration was followed by an infusion of lepirudin (bolus 0.1 mg kg-1, continuous infusion of 0.1 mg kg-1 h-1, n = 12) or saline (n = 12).

RESULTS

Plasma VEGF increased from a mean of 15.1 pg mL-1 to 74.6 pg mL-1 5 h after LPS (P < 0.003). Body temperature, pulse rate, leukcytes, prothrombin fragment 1 + 2 (F1 + 2) and lactoferrin increased and platelets decreased after LPS (P < 0.05). The LPS-induced increase in VEGF was paralleled by the neutrophil cell degranulation marker lactoferrin but not by F1 + 2, and was not affected by lepirudin, which blunted F1 + 2 formation (P < 0.05).

CONCLUSIONS

Inflammation-induced activation of leukcytes rather than platelets plays a role in the marked increase in VEGF, which cannot be abrogated by antithrombotic therapy.

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.

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

OBJECTIVE

Rheumatoid arthritis (RA) is an inflammatory disease and an angiogenic disease. However, the molecular mechanisms promoting angiogenesis in RA are not clearly identified. Our objective was to study the role of an endothelium-specific receptor tyrosine kinase, Tie2, in angiogenesis of inflammatory arthritis.

METHODS

Expression of Tie2 and its ligand, angiopoietin 1 (Ang1), in human synovium was examined by immunohistochemistry and Western blot. A novel synovium vascular window model was established to study the role of Tie2 in angiogenesis in vivo. Primary cultured endothelial cells and synoviocytes were used to study tumor necrosis factor alpha (TNF alpha)-induced Tie2 and Ang1 expression.

RESULTS

Tie2 was implicated in pathologic angiogenesis. We observed that Tie2 and Ang1 were elevated in human RA synovium. Using a novel collagen-induced arthritis synovial window model, we demonstrated that Tie2 signaling regulated arthritis angiogenesis in vivo. We also showed that Tie2 mediated TNF alpha-induced angiogenesis in a mouse cornea assay. In addition, we observed that TNF alpha can regulate Tie2 activation in multiple ways that may involve interactions between endothelial cells and synoviocytes. TNF alpha up-regulates Tie2 in endothelial cells through nuclear factor kappa B, and it up-regulates Ang1 in synoviocytes. These findings suggest paracrine regulation of angiogenesis between endothelial cells and synoviocytes.

CONCLUSION

This study demonstrates that Tie2 regulates angiogenesis in inflammatory synovium. Tie2 signaling is an important angiogenic mediator that links the proinflammatory cytokine TNF alpha to pathologic angiogenesis.

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.

Transgenic delivery of VEGF to mouse skin leads to an inflammatory condition resembling human psoriasis

Gene therapy approaches involving vascular endothelial growth factor (VEGF) to promote therapeutic angiogenesis are under consideration for conditions ranging from ischemic heart disease to nonhealing skin ulcers. Here we make the surprising observation that the transgenic delivery of VEGF to the skin results in a profound inflammatory skin condition with many of the cellular and molecular features of psoriasis, including the characteristic vascular changes, epidermal alterations, and inflammatory infiltrates. Even longstanding psoriatic disease remains dependent on the transgenic VEGF in this model because it can be effectively reversed by the addition of VEGF Trap, a potent VEGF antagonist. Previous attempts to faithfully replicate the psoriatic phenotype through the transgenic delivery of epidermal keratinocyte growth factors or inflammatory mediators generated phenotypes with only partial resemblance to human psoriasis, leaving unanswered questions about the etiology of this disease. The ability of transgenic VEGF to induce a psoriasiform phenotype suggests a new etiology and treatment approach for this disease and further substantiates emerging concerns about possible proinflammatory adverse effects that might be associated with therapeutic attempts to deliver VEGF.

Heterogeneous requirement of IkappaB kinase 2 for inflammatory cytokine and matrix metalloproteinase production in rheumatoid arthritis: implications for therapy

OBJECTIVE

To investigate the potential role of IkappaB kinase 1 (IKK-1) and IKK-2 in the regulation of nuclear factor kappaB (NF-kappaB) activation and the expression of tumor necrosis factor alpha (TNFalpha), as well as interleukin-1beta (IL-1beta), IL-6, IL-8, vascular endothelial growth factor (VEGF), and matrix metalloproteinases (MMPs), in rheumatoid arthritis (RA).

METHODS

Recombinant adenoviruses expressing beta-galactosidase, dominant-negative IKK-1 and IKK-2, or IkappaBalpha were used to infect ex vivo RA synovial membrane cultures and synovial fibroblasts obtained from patients with RA undergoing joint replacement surgery, or human dermal fibroblasts, human umbilical vein endothelial cells (HUVECs), and monocyte-derived macrophages from healthy volunteers. Then, their effect on the spontaneous or stimulus-induced release of inflammatory cytokines, VEGF, and MMPs from RA synovial membrane cells was examined.

RESULTS

IKK-2 was not required for lipopolysaccharide (LPS)-induced NF-kappaB activation or TNFalpha, IL-6, or IL-8 production in macrophages, but was essential for this process in response to CD40 ligand, TNFalpha, and IL-1. In synovial fibroblasts, dermal fibroblasts, and HUVECs, IKK-2 was also required for LPS-induced NF-kappaB activation and IL-6 or IL-8 production. In RA synovial membrane cells, IKK-2 inhibition had no effect on spontaneous TNFalpha production but significantly reduced IL-1beta, IL-6, IL-8, VEGF, and MMPs 1, 2, 3, and 13.

CONCLUSION

Our study demonstrates that IKK-2 is not essential for TNFalpha production in RA. However, because IKK-2 regulates the expression of other inflammatory cytokines (IL-1beta, IL-6, and IL-8), VEGF, and MMPs 1, 2, 3, and 13, which are involved in the inflammatory, angiogenic, and destructive processes in the RA joint, it may still be a good therapeutic target.

Anti-interleukin-6 receptor antibody therapy reduces vascular endothelial growth factor production in rheumatoid arthritis

OBJECTIVE

To investigate whether interleukin-6 (IL-6) is a regulator of vascular endothelial growth factor (VEGF) in rheumatoid arthritis (RA).

METHODS

Serum VEGF levels in RA patients were assayed before and after 8 weeks or 24 weeks of maintenance therapy with humanized anti-IL-6 receptor monoclonal antibody (anti-IL-6R mAb). VEGF secreted by RA synovial fibroblasts cultured in the presence of IL-6, IL-1beta, and/or tumor necrosis factor alpha (TNFalpha) was measured. The inhibitory effect of anti-IL-6R mAb, recombinant IL-1 receptor antagonist (IL-1Ra), and anti-TNFalpha mAb on VEGF production was also examined.

RESULTS

Serum VEGF levels in RA patients before anti-IL-6R mAb therapy were significantly higher than those in healthy controls (P < 0.0005). Treatment of RA patients with anti-IL-6R mAb normalized serum VEGF levels. In the in vitro study, IL-6 and IL-1beta each induced a slight amount of VEGF production in synovial cells, but TNFalpha did not. Although VEGF-inducing activity of these cytokines was not remarkable when they were added alone, IL-6 acted synergistically with IL-1beta or TNFalpha to induce VEGF production. There was no synergistic effect between IL-1beta and TNFalpha. In the presence of all of these cytokines, anti-IL-6R mAb eliminated the synergistic effect of IL-6, IL-1beta, and TNFalpha, while IL-1Ra or anti-TNFalpha mAb did not.

CONCLUSION

Anti-IL-6R mAb therapy reduced VEGF production in RA. IL-6 is the pivotal cytokine that induces VEGF production in synergy with IL-1beta or TNFalpha, and this may be the mechanism by which IL-6 blockade effectively suppresses VEGF production in synovial fibroblasts.

The angiogenic peptide vascular endothelial growth factor (VEGF) is expressed during the remodeling of free tendon grafts in sheep

BACKGROUND

Angiogenesis is important for the remodeling of autologous tendon grafts. A sheep model was used to examine the expression of the angiogenic peptide vascular endothelial growth factor (VEGF) in autologous tendon grafts after anterior cruciate ligament (ACL) reconstruction.

METHODS

Merino sheep underwent ACL reconstruction with an autologous Achilles tendon split graft. VEGF and its receptors, the Fms-like tyrosine kinase receptor (FLT-1, VEGFR-1) and the kinase insert domain-containing receptor KDR (VEGFR-2/FLK-1) were detected immunohistochemically. Reverse transcription-polymerase chain reaction (RT-PCR) was performed to detect which of the different VEGF splice forms are expressed during ACL remodeling.

RESULTS

At 6 weeks, light microscopy showed zones with hypocellular necrotic graft tissue in the central part surrounded by hypercellular and hypervascularized reparative tissue invading the former graft tissue from the periphery. In contrast to the necrotic tissue, all cell types of the reparative tissue labeled strongly positive for VEGF. The VEGF receptors FLT-1 and KDR could be detected on endothelial cells of blood vessels. At 12 weeks, the complete graft diameter showed an increased vascular density (anti-factor VIII immunoreactivity), but zones of non-remodeled former graft tissue could not be found. Fusiform fibroblasts labeled strongly for VEGF. At 24 weeks, VEGF immunostaining decreased, and at 52 and 104 weeks, the grafts were largely VEGF-negative. RT-PCR supported the immunohistochemical results regarding VEGF expression and showed further that the splice variants VEGF(120 )and VEGF(164) are expressed during angiogenesis during the remodeling of tendons.

CONCLUSION

We conclude that the angiogenic peptide VEGF plays a role in tendon graft remodeling.

VEGF expression in human macrophages is NF-kappaB-dependent: studies using adenoviruses expressing the endogenous NF-kappaB inhibitor IkappaBalpha and a kinase-defective form of the IkappaB kinase 2

Vascular endothelial growth factor (VEGF) is the most endothelial cell-specific angiogenic factor characterised to date, and it is produced by a variety of cell types. In macrophages, VEGF has been shown to be upregulated by the inflammatory mediator lipopolysaccharide (LPS) and by engagement of CD40 by CD40 ligand (CD40L). Because LPS and CD40L activate nuclear factor-kappaB (NF-kappaB) in monocytes, we investigated in this study whether VEGF production in macrophages, when stimulated with either LPS or CD40L, is NF-kappaB-dependent. We used adenoviral constructs over-expressing either IkappaBalpha (AdvIkappaBalpha), the endogenous inhibitor of NF-kappaB, or a kinase-defective mutant of IKK-2 (AdvIKK-2dn), an upstream activator of IkappaBalpha, to infect normal human monocyte-derived macrophages. We observed that LPS-induced production of VEGF in human macrophages was almost completely inhibited (>90%) following adenoviral transfer of IkappaBalpha. In addition, we observed significant inhibition of the CD40L-induced VEGF production in macrophages following infection with AdvIkappaBalpha. Expression of IKK-2dn in macrophages decreased VEGF production in response to LPS or CD40L by approximately 50%, suggesting that in addition to IKK-2, other kinases might be involved in NF-kappaB activation. These results show for the first time that VEGF production in human macrophages is NF-kappaB dependent. NF-kappaB regulates many of the genes involved in immune and inflammatory responses, and our study adds the angiogenic cytokine VEGF to the list of NF-kappaB-dependent cytokines.

Upregulated hypoxia inducible factor-1alpha and -2alpha pathway in rheumatoid arthritis and osteoarthritis

The pathogenesis of rheumatoid arthritis (RA) and osteoarthritis (OA) remains obscure, although angiogenesis appears to play an important role. We recently confirmed an overexpression of two angiogenic factors, namely vascular endothelial growth factor (VEGF) and platelet-derived endothelial cell growth factor (PD-ECGF), by the lining and stromal cells of the synovium in both conditions. Because hypoxia inducible factor (HIF)-1alpha and HIF-2alpha are essential in regulating transcription of the VEGF gene, active participation of HIF-alpha molecules in the pathogenesis of these arthritides is anticipated. We investigated the immunohistochemical expression of HIF-1alpha and HIF-2alpha in the synovium of 22 patients with RA, 34 patients with OA and 22 'normal' nonarthritic individuals, in relation to VEGF, VEGF/KDR (kinase insert domain protein receptor) vascular activation, PD-ECGF and bcl-2. A significant cytoplasmic and nuclear overexpression of HIF-1alpha and HIF-2alpha was noted in the synovial lining and stromal cells of both diseases relative to normal. Overexpression of HIF-alphas was related to high microvessel density, high PD-ECGF expression and high VEGF/KDR receptor activation, suggesting HIF-alpha-dependent synovial angiogenesis in OA. By contrast, the activation of the angiogenic VEGF/KDR pathway was persistently increased in RA, as indeed was microvessel density and the expression of PD-ECGF, irrespective of the extent of HIF-alpha expression, indicating a cytokine-dependent angiogenesis. In all cases, the VEGF/KDR vascular activation was significantly lower in OA than in RA, suggesting a relative failure of the HIF-alpha pathway to effectively produce a viable vasculature for OA, which is consistent with the degenerative nature of the disease. The activation of the HIF-alpha pathway occurs in both RA and OA, although for unrelated reasons.

Etanercept for the treatment of rheumatoid arthritis

BACKGROUND

Etanercept is a soluble tumour necrosis factor alpha-receptor DMARD for the treatment of rheumatoid arthritis (RA).

OBJECTIVES

To assess the efficacy and safety of etanercept for the treatment of RA.

SEARCH STRATEGY

Five electronic databases were searched from 1966 to February 2003 with no language restriction.

SELECTION CRITERIA

All randomized controlled trials (minimum 6 month duration) comparing three possible combinations 1) etanercept (10 mg or 25 mg twice weekly) with methotrexate (MTX) to MTX alone 2) etanercept to MTX, or 3) etanercept to placebo were eligible.

DATA COLLECTION AND ANALYSIS

Two reviewers extracted data and assessed the methodological quality of the trails. The American College of Rheumatology (ACR) core set of disease activity measures for RA clinical trials, radiographic, withdrawals and toxicity outcomes were analyzed.

MAIN RESULTS

Three trials were included in this review. Two trials compared an experimental group who were started on etanercept compared to a control group; both groups had the same ongoing background therapy of nonsteroidals in both trials plus in one trial one group was on stable methotrexate. In these two trials the ACR 20, ACR 50 and ACR 70 response rates at 6 months were statistically significantly and clinically important with etanercept 25 mg subcutaneous injections (SC) twice weekly. Sixty-four percent of people receiving etanercept ache vied an ACR 20 response compared to 15% of controls and the number needed to treat (NNT) with etanercept is 2 people. Thirty-nine percent of those receiving etanercept achieved an ACR 50 response compared to 4% of taking control treatment and the NNT is three. Fifteen percent of people taking etanercept achieved an ACR 70 compared to 1% of controls with a NNT of 7 people. In the third trial of starting etanercept compared to starting methotrexate the number of participants who achieved an ACR 20, 50 or response at 6 and 12 months were not statistically significant for either etanercept dose. Etanercept treatment showed a statistically significantly and clinically important affect on joint damage as measured by the Sharp erosion score. Among participants who received etanercept 72% had no increase in their erosion score compared to 60% of participants in the methotrexate group. Withdrawal and toxicity results were acceptable.

REVIEWER'S CONCLUSIONS

Etanercept 25 mg SC twice weekly was more efficacious than control treatment for ACR 20, 50 and 70 at 6 months, and over 12 months it slowed joint damage.

The angiogenesis inhibitor protease-activated kringles 1-5 reduces the severity of murine collagen-induced arthritis

During rheumatoid arthritis there is enlargement and increased cellularity of the synovial lining of joints, before invasion by the synovium of the underlying cartilage and bone. This increased tissue mass requires a network of blood vessels to supply nutrients and oxygen. Disruption of synovial angiogenesis is thus a desirable aim of antiarthritic therapies. Protease-activated kringles 1-5 (K1-5) is an angiogenesis inhibitor related to angiostatin. In common with angiostatin, K1-5 contains the first four kringle domains of plasminogen, but also encompasses the kringle 5 domain, which confers enhanced antiangiogenic activity when compared with angiostatin. The purpose of the present study was to assess the effect on murine arthritis of K1-5. Arthritis was induced in DBA/1 mice by a single injection of bovine collagen. Treatment with K1-5 was commenced on the day of arthritis onset and continued for 10 days, until the end of the experiment. Daily intraperitoneal administration of K1-5 (2 mg/kg body weight) significantly reduced both paw swelling and clinical score (a composite index of the number of arthritic limbs and the severity of disease). The clinical efficacy of this treatment was reflected by a reduction in joint inflammation and destruction, as assessed histologically. These data suggest that antiangiogenic therapies, which block formation of new blood vessels and hence reduce synovial expansion, might be effective in treating rheumatoid arthritis.

Interleukin-15 inhibits sodium nitroprusside-induced apoptosis of synovial fibroblasts and vascular endothelial cells

OBJECTIVE

One of the pathologic hallmarks of juvenile rheumatoid arthritis (JRA) is a tumor-like expansion of inflamed synovial tissue, or pannus, which causes much of the joint damage in this disease. The expansion of pannus is supported by extensive formation of new blood vessels. We have previously shown that revascularization of minced JRA synovial tissues engrafted into SCID mice correlated with the intensity of inflammatory activity in the tissues and with interleukin-15 (IL-15) expression. Since synovial vascular endothelial cells (VECs) expressed IL-15 receptors, the present study was undertaken to investigate the hypothesis that IL-15 might play a role in neovascularization of the pannus.

METHODS

To evaluate IL-15 for possible angiogenic activity, we assessed the ability of recombinant human IL-15 (rHuIL-15) to induce VEC growth directly and to stimulate synovial cells to produce endothelial growth factors. Since IL-15 had been shown to inhibit apoptosis of certain immune cells, we were also interested in whether it might have similar effects on VECs. Apoptosis was induced by addition of sodium nitroprusside (SNP) at 1-2 mM to >80% confluent primary VECs, and numbers of apoptotic cells were determined by annexin V assay.

RESULTS

Addition of rHuIL-15 at 10-100 ng/ml to primary synovial fibroblast cultures failed to up-regulate expression of vascular endothelial growth factor and angiopoietin 1 by these cells. Although rHuIL-15 failed to induce a mitogenic response of VECs, it promoted survival of these cells on Matrigel. Preincubation of VECs with rHuIL-15 at 50 ng/ml significantly reduced the proportion of VECs undergoing apoptosis.

CONCLUSION

IL-15 promotes survival of VECs on Matrigel and inhibits SNP-induced apoptosis of endothelial cells. We hypothesize that this mechanism may be relevant to the stabilization of newly formed vascular structures in JRA synovium.

Pharmaco-redox regulation of cytokine-related pathways: from receptor signaling to pharmacogenomics

Cytokines represent a multi-diverse family of polypeptide regulators; they are relatively low molecular weight (< 30 kDa), pharmacologically active proteins that are secreted by one cell for the purpose of altering either its own functions (autocrine effect) or those of adjacent cells (paracrine effect). Cytokines are small, nonenzymatic glycoproteins whose actions are both diverse and overlapping (specificity/redundancy) and may affect diverse and overlapping target cell populations. In many instances, individual cytokines have multiple biological activities. Different cytokines can also have the same activity, which provides for functional redundancy (network) within the inflammatory and immune systems. As biological cofactors that are released by specific cells, cytokines have specific effects on cell-cell interaction, communication, and behavior of other cells. As a result, it is infrequent that loss or neutralization of one cytokine will markedly interfere with either of these systems. The biological effect of one cytokine is often modified or augmented by another. Because an interdigitating, redundant network of cytokines is involved in the production of most biological effects, both under physiologic and pathologic conditions, it usually requires more than a single defect in the network to alter drastically the outcome of the process. This fact, therefore, may have crucial significance in the development of therapeutic strategies for biopharmacologic intervention in cytokine-mediated inflammatory processes and infections.

Inhibition of interleukin-1 but not tumor necrosis factor suppresses neovascularization in rat models of corneal angiogenesis and adjuvant arthritis

OBJECTIVE

To assess the capacities of the cytokine inhibitors interleukin-1 receptor antagonist (IL-1Ra; anakinra) and PEGylated soluble tumor necrosis factor receptor I (PEG sTNFRI; pegsunercept) to suppress neovascularization.

METHODS

A corneal angiogenesis assay was performed by implanting nylon discs impregnated with an angiogenic stimulator (basic fibroblast growth factor or vascular endothelial growth factor) into one cornea of female Sprague-Dawley rats. Animals were treated with IL-1Ra or PEG sTNFRI for 7 days, after which new vessels were quantified. In a parallel study, male Lewis rats with mycobacteria-induced adjuvant-induced arthritis were treated with IL-1Ra or PEG sTNFRI for 7 days beginning at disease onset, after which scores for inflammation and bone erosion as well as capillary counts were acquired from sections of arthritic hind paws.

RESULTS

Treatment with IL-1Ra yielded a dose-dependent reduction in growth factor-induced corneal angiogenesis, while PEG sTNFRI did not. IL-1Ra, but not PEG sTNFRI, significantly reduced the number of capillaries in arthritic paws, even though both anticytokines reduced inflammation and bone erosion to a similar degree.

CONCLUSION

These data support a major role for IL-1, but not TNFalpha, in angiogenesis and suggest that an additional antiarthritic mechanism afforded by IL-1 inhibitors, but not anti-TNF agents, is the suppression of the angiogenic component of pannus.

Soluble adhesion molecules (ICAM-1, VCAM-1, and E-selectin) and vascular endothelial growth factor (VEGF) in patients with distinct variants of rheumatoid synovitis

BACKGROUND

Cell adhesion molecules and endothelial growth factors have an important role in the infiltrating of rheumatoid synovium with mononuclear cells, leading to the initiation and progression of the disease.

OBJECTIVE

To investigate whether the serum profile of soluble adhesion molecules and of vascular endothelial growth factor (VEGF) is associated with the histological appearance of rheumatoid arthritis (RA).

METHODS

Serum levels of soluble intercellular adhesion molecule-1 (sICAM-1), vascular cell adhesion molecule-1 (sVCAM-1), E-selectin (sE-selectin), and VEGF were assessed by enzyme linked immunosorbent assay (ELISA) in 40 patients with RA and 32 patients with osteoarthritis (OA).

RESULTS

Histological analysis of synovium specimens distinguished two types of rheumatoid synovitis. Twenty four RA samples presented diffuse infiltrates of mononuclear cells without any further microanatomical organisation, whereas in the remaining 16 samples lymphocytic follicles with germinal centre-like structures were identified. In comparison with patients with OA, constituting a control group, higher serum concentrations of sICAM-1 (p<0.001), sVCAM-1 (p<0.001), sE-selectin (p<0.01), and VEGF (p<0.001) were detected in patients with RA. Raised concentrations of sICAM-1, sVCAM-1, and VEGF dominated in the serum of patients with RA with follicular synovitis compared with those with diffuse synovitis (p<0.01 for all comparisons). The serum concentrations of sICAM-1, sVCAM-1, and VEGF correlated with markers of disease activity such as the erythrocyte sedimentation rate and C reactive protein levels. Furthermore, the clinical data analysed in our study indicated that patients with RA with follicular synovitis tend to have more severe disease.

CONCLUSIONS

The distinct histological appearances of rheumatoid synovitis associated with different serum profiles of sICAM-1, sVCAM-1, and VEGF reflect varied clinical activity of the disease and confirm RA heterogeneity. Patients with different histological forms of synovitis may respond differently to the treatment regimens.

Cytokines and anti-cytokine biologicals in autoimmunity: present and future

The increasing understanding of the role of cytokines in autoimmunity, and the observation that tumour necrosis factor alpha (TNFalpha) is central to the inflammatory and destructive process common to several human autoimmune diseases, has led to a new generation of therapeutics, the TNFalpha blocking agents. In this article, we review the current knowledge of the role of cytokines in autoimmunity as unravelled by studies both in the laboratory and the clinic. In addition, we discuss future prospects of the anti-TNFalpha therapy that may involve combination therapy with other anti-cytokine or anti-T cell biologicals, or the use of small chemicals targeting molecules involved in TNFalpha production such as NF-kappaB and p38 MAPK. The future developments of anti-TNFalpha and anti-cytokine therapy in general will be interesting.

Serum and synovial fluid concentration of vascular endothelial growth factor in juvenile idiopathic arthritides

OBJECTIVE

To evaluate the role of vascular endothelial growth factor (VEGF) in the pathogenesis of local joint inflammation in juvenile idiopathic arthritis (JIA).

METHODS

Sera from 50 patients affected with JIA and 10 age-matched healthy controls were tested with a commercial ELISA for VEGF. Corresponding synovial fluid (SF) concentrations of VEGF and p75 soluble tumour necrosis factor receptor (sTNFR) were evaluated in 20 active JIA patients.

RESULTS

Serum concentrations of VEGF were significantly higher in patients with active polyarticular disease than in patients with active and inactive oligoarticular disease and healthy controls. In JIA patients, serum concentrations of VEGF displayed a significant correlation with a number of clinical and laboratory parameters of disease activity. VEGF concentrations in SF were significantly higher than those detected in corresponding sera. Moreover, a clear correlation was found between corresponding SF and serum VEGF concentrations. In SF, VEGF showed a strong positive correlation with p75 sTNFR.

CONCLUSIONS

Concentrations of VEGF in SF in patients with JIA are higher than corresponding serum concentrations, suggesting that this pro-angiogenic factor may have a major role in the outgrowth of hyperplastic pannus and tissue damage at the site of tissue inflammation.

Tumor necrosis factor-alpha blockade: a novel therapy for rheumatic disease

Overproduction of tumor necrosis factor-alpha (TNF) plays a key role in the pathogenesis of rheumatoid arthritis (RA) and other chronic inflammatory diseases. In RA, excessive production of TNF-alpha can drive synovial inflammation and proliferation as well as degradation of articular cartilage and bone. The importance of TNF-alpha in these mechanisms is supported by the results of clinical trials. In these studies, treatment with etanercept and infliximab, two recently approved TNF-alpha inhibitors, has been shown to significantly decrease the signs and symptoms of joint inflammation and slow the progression of radiological joint damage. Although TNF-alpha inhibitors have had acceptable toxicity in clinical trials, commercial use of these agents has produced growing concerns about the potential risk for opportunistic infections, most notably the reactivation of latent tuberculosis. The TNF-alpha inhibitors stand as a powerful example of the therapeutic potential of a targeted biological agent. Longer-term clinical experience with these cytokine antagonists will illuminate their optimal use in RA and other rheumatic diseases.

VEGF and imaging of vessels in rheumatoid arthritis

Angiogenesis is a prominent feature of rheumatoid synovitis. Formation of new blood vessels permits a supply of nutrients and oxygen to the augmented inflammatory cell mass and so contributes to perpetuation of joint disease. Vascular endothelial growth factor (VEGF) is a potent endothelial cell-specific growth factor that is upregulated by proinflammatory cytokines and by hypoxia. Serum VEGF concentrations are elevated in rheumatoid arthritis (RA) and correlate with disease activity. Furthermore, serum VEGF measured at first presentation in RA is highly significantly correlated with radiographic progression of disease over the subsequent year. Power Doppler ultrasonography is a sensitive method for demonstrating the presence of blood flow in small vessels and there is a very close relation between the presence or absence of vascular flow signal on power Doppler imaging and the rate of early synovial enhancement on dynamic gadolinium-enhanced magnetic resonance imaging (MRI) of joints with RA. Images obtained by both dynamic enhanced MRI and power Doppler ultrasonography correlate with vascularity of synovial tissue as assessed histologically. In early RA, there is a striking association between joint erosions assessed on high-resolution ultrasonography and vascular signal in power Doppler mode. Collectively, these findings implicate vascular pannus in the erosive phase of disease and strongly suggest that proangiogenic molecules such as VEGF are targets for novel therapies in RA. Animal model data supports this concept. It seems likely that serological and imaging measures of vascularity in RA will become useful tools in the assessment of disease activity and response to therapy.

Long term anti-tumour necrosis factor alpha monotherapy in rheumatoid arthritis: effect on radiological course and prognostic value of markers of cartilage turnover and endothelial activation

OBJECTIVES

To investigate the effect of prolonged neutralisation of tumour necrosis factor alpha (TNFalpha) on the radiological course in rheumatoid arthritis (RA). To assess whether the radiological course can be predicted by clinical variables or biological markers of cartilage and synovium turnover and of endothelial activation.

PATIENTS AND METHODS

Forty seven patients with active RA enrolled at our centre in monotherapy trials with adalimumab (D2E7), a fully human anti-TNFalpha monoclonal antibody, were studied for two years. Radiographs of hands and feet obtained at baseline and after one and two years were scored in chronological order by a single, blinded observer using the modified Sharp method. Radiological course was classified as stable or progressive using the smallest detectable difference as cut off point. The relation between radiological course and serum markers of cartilage and synovium turnover (metalloproteinases (MMP-1 and MMP-3), cartilage oligomeric matrix protein (COMP), human cartilage glycoprotein-39 (HC gp-39)), endothelial activation (soluble E-selectin and intercellular adhesion molecule (ICAM-1)), and integrated measures of disease activity were assessed using univariate and multivariate analysis.

RESULTS

Radiological evaluation was performed in 36 patients with paired sets of radiographs at baseline and two years. After two years a total of 15/36 (42%) presented no radiological progression. More patients with stable radiological course were still receiving anti-TNFalpha treatment after two years (13/15 (87%) v 11/21 (52%); p=0.03) and had lower baseline COMP and sICAM-1 levels (p=0.01 and 0.04, respectively) than those in the group with progressive disease. In a logistic regression model the combination of sustained TNF neutralisation and baseline COMP and sICAM-1 levels was predictive for radiological outcome (p=0.03). C reactive protein and disease activity score area under the curve were significantly correlated with changes in radiological scores after two years (r=0.40 and 0.37, p<0.05). Long term TNFalpha neutralisation decreased the levels of COMP, sICAM, MMPs, and HC gp-39, but not sE-selectin.

CONCLUSION

The results suggest that long term monotherapy with anti-TNFalpha has a positive effect on radiological outcome and modulates cartilage and synovium turnover as measured by biological markers. Baseline serum sICAM-1 levels and COMP levels may be helpful to identify patients with progressive or non-progressive radiological outcome.

Stromal cell-derived factor 1 (CXCL12) induces monocyte migration into human synovium transplanted onto SCID Mice

OBJECTIVE

The mechanisms by which monocyte/macrophage cells migrate to the joint involve a series of integrated adhesion and signaling events in which chemokines and their receptors are strongly implicated. This study was undertaken to investigate the hypothesis that stromal cell-derived factor 1 (SDF-1), a CXC chemokine (CXCL12), plays a critical role in monocyte/macrophage localization to synovium.

METHODS

SDF-1 and CXC receptor 4 (CXCR4) expression in rheumatoid arthritis (RA) and osteoarthritis synovium and graft SDF-1, tumor necrosis factor alpha (TNF alpha), and human and murine vascular markers were examined by immunohistochemistry and double-immunofluorescence. The functional capacity of SDF-1 to modulate monocyte migration into joints was investigated by examining the localization of pro-myelomonocytic U937 cells into synovial tissue transplanted into SCID mice. SDF-1, TNF alpha, or saline was injected into graft sites and response determined by the number of fluorescently labeled U937 cells (injected intravenously) detected in grafts by ultraviolet microscopy.

RESULTS

SDF-1 and CXCR4 were highly expressed in CD68+ cells in the RA synovium. SDF-1 induced U937 cell migration in vitro and in vivo in a dose-dependent manner and, in vivo, SDF-1 was more effective than TNF alpha. In contrast to TNF alpha, SDF-1 did not induce intracellular adhesion molecule 1 in transplant microvasculature. Furthermore, intragraft injection of SDF-1 did not up-regulate TNF alpha, or vice versa.

CONCLUSION

This study demonstrates, for the first time, that SDF-1 is functional in vivo when injected into synovial grafts. In addition, SDF-1 is more potent than TNF alpha, and its mechanisms of action appear to be autonomous. Therefore, SDF-1 may be an important TNF-independent molecule involved in the migration to and retention of inflammatory effector cells in the joint.

Use of anti-platelet-endothelial cell adhesion molecule-1 antibody in the control of disease progression in established collagen-induced arthritis in DBA/1J mice

Platelet-endothelial cell adhesion molecule-1 (PECAM-1) is expressed on the membrane of leukocytes and vascular endothelial cells. PECAM-1 has been shown to play an important role in the process of leukocyte transmigration in various animal models of acute inflammation. We investigated the role of PECAM-1 in the progression of arthritis by systemically administering anti-murine PECAM-1 monoclonal antibody, 2H8, to DBA/1J mice with collagen-induced arthritis (CIA). Subcutaneous administration of dexamethasone (0.5 mg/kg per 2 days) significantly reduced hindpaw swelling and the clinical score of established CIA. Intraperitoneal administration of 2H8 (0.25 mg/mouse per 2 days) significantly inhibited hindpaw swelling in a time-dependent manner. 2H8 also significantly prevented further deterioration in the clinical score, but failed to reverse joint destruction discernible at the histological level. Both dexamethasone and 2H8 inhibited body weight decrease by preventing the further development of arthritis. Histopathological assessment revealed that 2H8, as well as dexamethasone, inhibited inflammatory cell transmigration into the synovium of the hind paw joint and ameliorated synovitis and cartilage erosion. These results suggest that PECAM-1 plays an important role in the progression of CIA and that an inhibitor of PECAM-1 might have therapeutic value for clinical treatment of rheumatoid arthritis.

Angiogenesis in rheumatoid arthritis

The expansion of the synovial lining of joints in rheumatoid arthritis (RA) and the subsequent invasion by the pannus of underlying cartilage and bone necessitate an increase in the vascular supply to the synovium, to cope with the increased requirement for oxygen and nutrients. The formation of new blood vessels - termed 'angiogenesis' - is now recognised as a key event in the formation and maintenance of the pannus in RA. This pannus is highly vascularised, suggesting that targeting blood vessels in RA may be an effective future therapeutic strategy. Disruption of the formation of new blood vessels would not only prevent delivery of nutrients to the inflammatory site, but could also lead to vessel regression and possibly reversal of disease. Although many proangiogenic factors are expressed in the synovium in RA, the potent proangiogenic cytokine vascular endothelial growth factor (VEGF) has been shown to a have a central involvement in the angiogenic process in RA. The additional activity of VEGF as a vascular permeability factor may also increase oedema and hence joint swelling in RA. Several studies have shown that targeting angiogenesis in animal models of arthritis ameliorates disease. Our own study showed that inhibition of VEGF activity in murine collagen-induced arthritis, using a soluble VEGF receptor, reduced disease severity, paw swelling, and joint destruction. Although no clinical trials of anti-angiogenic therapy in RA have been reported to date, the blockade of angiogenesis - and especially of VEGF - appears to be a promising avenue for the future treatment of RA.

Serum matrix metalloproteinases and tissue inhibitors of metalloproteinases in different histological variants of rheumatoid synovitis

OBJECTIVE

Rheumatoid synovitis is characterized by an invasive and tissue-destructive infiltrate of lymphocytes, macrophages and synoviocytes. Matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs) produced by these cells are important in the remodelling of the articular tissues in rheumatoid arthritis (RA). The aim of this study was to explore whether the serum concentrations of MMPs and their inhibitors were correlated with the histological appearance of the disease.

METHODS

Tissue and serum samples were obtained from 37 patients with clinically active RA and 30 with osteoarthritis (OA). Morphological analysis allowed the division of RA synovial specimens into two distinct types. In 22 samples only diffuse infiltrates of mononuclear cells without further microanatomical organization were found. In 15 specimens we observed lymphocytic conglomerates with germinal centre-like structures. Serum concentrations of interstitial collagenase (MMP-1), stromelysin-1 (MMP-3), gelatinase B (MMP-9), TIMP-1 and TIMP-2 were measured with an ELISA technique.

RESULTS

Unique serum profiles of MMPs and TIMPs were identified in each of the two histological types of RA synovitis. The serum concentrations of MMP-1, MMP-3 and MMP-9 were higher in RA patients than in OA patients used as a control group (P<0.001 for all comparisons). These three MMPs dominated in the serum of RA patients with follicular synovitis compared with those with diffuse synovitis (P<0.05, P<0.01 and P<0.001 respectively). The analysis of the serum concentrations of TIMP-1 and TIMP-2 showed that their levels were also elevated in RA patients compared with OA patients (P<0.001 and P<0.01 respectively). Only TIMP-1 was found in a significantly higher concentration in the serum of RA patients with follicular synovitis than in those with diffuse synovitis (P<0.05). The serum concentrations of MMPs and TIMP-1 clearly identified patients with two different histological types of rheumatoid synovitis and with OA. Additionally, the analysis of clinical data showed that the rheumatoid disease in patients with follicular synovitis seemed to be more active than in those with diffuse synovitis.

CONCLUSION

The morphological appearance of rheumatoid synovitis and the serum MMP and TIMP-1 profile were correlated with the clinical activity of the disease, confirming the heterogeneity of RA. These associations also suggest that patients with different histological forms of RA might require different treatment regimens.

Discovery of TNF-alpha as a therapeutic target in rheumatoid arthritis: preclinical and clinical studies

The development of effective new treatments is greatly facilitated by the understanding of the mechanisms of disease. In rheumatoid arthritis, there has been progress in understanding its immunology, the HLA class II predisposition including the 'shared epitope' and more recently in understanding the importance of proinflammatory cytokines. Here we review our work in defining TNFalpha as a therapeutic target in rheumatoid arthritis, from an understanding of molecular pathogenesis in vitro, to formal proof in the clinic in vivo. There is now extensive clinical use of anti-TNFalpha biologicals for severe rheumatoid arthritis in the US and Europe.