Angiogenesis in rheumatoid arthritis

Clinical value of blocking IL-6 receptor

PURPOSE OF REVIEW

Interleukin-6 (IL-6) is a multifunctional cytokine that regulates inflammatory response and immune reaction. Overproduction of IL-6 is pathologically involved in inflammatory autoimmune diseases such as rheumatoid arthritis (RA) and juvenile idiopathic arthritis, and therefore, blocking IL-6 activity is one of therapeutic options for these diseases. Tocilizumab is a humanized anti-IL-6 receptor (IL-6R) antibody and inhibits IL-6 activity. There is now accumulating evidence that tocilizumab is therapeutically effective for patients with RA and other inflammatory autoimmune diseases. This article reviews the clinical value of blocking IL-6R.

RECENT FINDINGS

Tocilizumab, as monotherapy and in combination with methotrexate, has been shown to be effective for RA patients with insufficient efficacy to methotrexate or other disease-modifying antirheumatic drugs. These findings of tocilizumab have been expanded to patients refractory to tumor necrosis factor inhibitors. Tocilizumab also retards the progression of structural joint damage. Furthermore, a 5-year long-term safety and efficacy has been shown. Tocilizumab is also a promising therapeutic option for other rheumatic diseases such as systemic-onset juvenile idiopathic arthritis, adult-onset Still's disease, and Takayasu arteritis.

SUMMARY

Blocking IL-6R with tocilizumab represents a promising new treatment for RA and other inflammatory diseases. Large registry data will warrant the safety profile of tocilizumab.

Gene expression profiling as a tool for positional cloning of genes-shortcut or the longest way round

The identification of quantitative trait loci, QTL, in arthritis animal models is a straight forward process. However, to identify the underlying genes is a great challenge. One strategy frequently used, is to combine QTL analysis with genomic/proteomic screens. This has resulted in a number of publications where carefully performed genomic analyses present likely candidate genes for their respective QTL s. However, seldom the findings are reconnected to the QTL controlled phenotypes. In this review, we use our own data as an illustrative example that "very likely candidate genes" identified by genomic/proteomics is not necessarily the same as true QTL underlying genes.

Quantification of synovitis in rheumatoid arthritis: do we really need quantitative measurement of contrast-enhanced ultrasound?

OBJECTIVE

The quantification of synovitis is of great significance for adequate therapy management and follow-up in patients with Rheumatoid Arthritis (RA). The purpose of this study was to validate a semi-quantitative Power Doppler (PD) scoring system by comparing the PD scores to the objective measurement of the synovial inflammation using dynamic contrast-enhanced Pulse-Inversion Harmonic Imaging (PIHI).

MATERIALS AND METHODS

In 27 patients with RA, two radiologists performed semi-quantitative scoring of a PD examination, using a four-point scale from 0 to 3, in the metacarpophalangeal joints, proximal interphalangeal joints, and the wrists. The scores were compared to the area under the time-echo intensity curves obtained by contrast-enhanced PIHI examination. The interobserver agreement for PD scoring was evaluated using the Cohen's kappa test.

RESULTS

Preliminary results showed that the area under the curve of dynamic measurements of PIHI tended to correlate with PD scores. The interobserver agreement for PD scoring was good (kappa=0.768).

DISCUSSION

Based on comparisons with dynamic contrast-enhanced PIHI, semi-quantitative PD scoring might meet the criteria for a reliable, reproducible, and practical scoring system. Although further studies that would include a larger study population are required, our preliminary results show that PIHI may not provide a real benefit for quantification of synovitis in day-to-day practice.

Current concepts in the pathogenesis of early rheumatoid arthritis

Rheumatoid arthritis (RA) is a systemic inflammatory disease with a predilection for symmetrically distributed diarthroidal joints. It is clinically heterogeneous, with particular disease phenotypes defined according to a complex interplay of genes and the environment. In this chapter we first summarize current knowledge of RA genetic susceptibility, a field which has been transformed in recent years by powerful modern genotyping technologies. The importance of a recently described subclassification for the disease based upon the presence or absence of circulating autoantibodies to citrullinated peptides has further informed genetic studies, and we consider the implications for our understanding of RA pathogenesis. We then review the cellular and molecular processes that initiate and perpetuate joint destruction.

The hypoxic synovial environment regulates expression of vascular endothelial growth factor and osteopontin in juvenile idiopathic arthritis

OBJECTIVE

Synovial angiogenesis, a critical determinant of juvenile idiopathic arthritis (JIA) pathogenesis, is sustained by various mediators, including vascular endothelial growth factor (VEGF) and osteopontin (OPN). We characterized the contribution of the local hypoxic environment to VEGF and OPN production by monocytic cells recruited to the synovium in JIA.

METHODS

Paired synovial fluid (SF) and peripheral blood (PB) samples were collected from 20 patients with JIA. Mononuclear cells (MC) were isolated, and monocytic cells were purified by adherence, maintained in a hypoxic environment, or subjected to reoxygenation. VEGF and OPN protein concentrations were tested in SF, plasma, and culture supernatants by ELISA, and mRNA expression was assessed in freshly purified and cultured cells by reverse transcriptase-polymerase chain reaction. Synovial tissue was obtained at synovectomy from 4 patients with JIA, and analyzed by immunohistochemistry for VEGF, OPN, CD68, and hypoxia-inducible factor-1alpha (HIF-1alpha).

RESULTS

VEGF mRNA expression was increased in SFMC and SF monocytic cells compared to matched PBMC and PB monocytic cells or SF lymphocytes, correlating with significantly higher protein levels in SF relative to plasma samples. Accordingly, OPN mRNA expression in SF monocytic cells was associated with significant increase of SF protein. Immunohistochemistry revealed the presence of both factors in synovial tissues at the level of the lining and sublining layers, which colocalized with intense CD68 and HIF-1alpha staining, suggesting production by hypoxic synovial monocytic cells. VEGF and OPN expression was abrogated upon SF monocytic cell reoxygenation and maintained by exposure to prolonged hypoxia.

CONCLUSION

Hypoxic synovial monocytic cells are a likely source of VEGF and OPN in JIA. These data point to a role for hypoxia in the perpetuation of synovitis in JIA.

Contrast-enhanced Coded Phase-inversion Harmonic Sonography of Knee Synovitis Correlates with Histological Vessel Density: 2 Automated Digital Quantifications

Objective.

To use contrast-enhanced coded phase-inversion harmonic B-mode sonography to assess the acoustic enhancement of the synovial area of the knee; and to compare the data with the histological vessel density.

Methods.

Eleven patients eligible for a knee arthroscopy were studied. Acoustic quantification was carried out by a digital image analysis program that detects the time-dependent increase [intensity (time) = k × time + C] of gray-level intensity in all the pixels of a specific region of interest (ROI) following intravenous injection of the microbubble contrast agent sulfur hexafluoride. Echo-guided synovial biopsies were carried out in the same ROI. Synovial vessel areas were quantified after Factor VIII immunostaining of synovial biopsies using an automated digital image analysis.

Results.

Significant (p < 0.05) correlations were observed between histological vessel density and percentage of the synovial area with a k value > 0.01 (r = 0.93) and kmaxvalues (r = 0.79), as well as between the 2 latter parameters (r = 0.72). The histological vessel density and the 2 acoustic parameters were also significantly correlated with the logarithm of erythrocyte sedimentation rate (r = 0.77, r = 0.87, r = 0.67, respectively) and with log C-reactive protein serum concentration (r = 0.69, r = 0.83, r = 0.62, respectively).

Conclusion.

Contrast-enhanced coded phase-inversion harmonic B-mode sonography coupled with an appropriate data analysis method is a new tool to identify and quantify vessel density in knee synovitis.

The investigation of synovial genomic targets of bucillamine with microarray technique

OBJECTIVE

To identify the molecular mechanisms of bucillamine activity, global gene expression analysis and pathway analysis were conducted using IL-1 beta-stimulated human fibroblast-like synovial cells (FLS).

METHODS

Normal human FLS were treated with IL-1 beta in the presence or absence of 10 and 100 microM bucillamine for 6 h. Total RNA was extracted and global gene expression levels were detected using a 44 k human whole genome array. Data were analyzed using Ingenuity pathway analysis.

RESULTS

Numerous pathways were activated by IL-1 beta stimulation. At both concentrations, bucillamine suppressed nine signal pathways stimulated by IL-1 beta.

CONCLUSIONS

Bucillamine effectively inhibited fibroblast growth factor (FGF) signaling and tight junction signaling activated by IL-1 beta in FLS. Suppression of these signal pathways may correlate with the pharmacologic mechanisms of bucillamine. In particular, the suppression of FGF signaling by bucillamine is remarkable because the activation of FGF signaling may be involved in rheumatoid arthritis pathology.

Hypoxia. Regulation of NFkappaB signalling during inflammation: the role of hydroxylases

NFκB is a master regulator of innate immunity and inflammatory signalling. Microenvironmental hypoxia has long been identified as being coincident with chronic inflammation. The contribution of microenvironmental hypoxia to NFκB-induced inflammation has more recently been appreciated. Identification of the co-regulation of NFκB and hypoxia inducible factor (HIF) pathways by 2-oxo-glutarate-dependent hydroxylase family members has highlighted an intimate relationship between NFκB inflammatory signalling and HIF-mediated hypoxic signalling pathways. Adding another layer of complexity to our understanding of the role of NFκB inflammatory signalling by hypoxia is the recent recognition of the contribution of basal NFκB activity to HIF-1α transcription. This observation implicates an important and previously unappreciated role for NFκB in inflammatory disease where HIF-1α is activated. The present review will discuss recent literature pertaining to the regulation of NFκB inflammatory signalling by hypoxia and some of the inflammatory diseases where this may play an important role. Furthermore, we will discuss the potential for prolylhydroxylase inhibitors in inflammatory disease.

Antagonism of the human epidermal growth factor receptor family controls disease severity in murine collagen-induced arthritis

OBJECTIVE

To evaluate the therapeutic potential of the human epidermal growth factor receptor (HER) family inhibitor, herstatin, in an animal model of arthritis.

METHODS

Constructs of herstatin and modified tissue plasminogen activator (tPA)-herstatin were expressed in HEK 293T cells, and secreted protein was analyzed by Western blotting. Tissue PA-herstatin adenovirus (Ad-tPA-Her) was prepared, and titers established. Gene expression of Ad-tPA-Her was determined by polymerase chain reaction using HeLa cells. Pharmacokinetics of gene and protein expression in vivo in liver tissue and serum samples were confirmed via intravenous administration of Ad-tPA-Her. Clinical signs of disease were monitored in arthritic DBA/1 mice after therapeutic administration of Ad-tPA-Her, and histologic analysis of hind foot specimens was performed.

RESULTS

Native herstatin was not secreted in supernatants, while modified tPA-herstatin was detected in abundance. HeLa cells stably expressed the tPA-herstatin gene when infected with virus. Additionally, tPA-herstatin gene and protein expression was observed over time in mice treated with virus. Importantly, Ad-tPA-Her, when administered therapeutically to arthritic mice, controlled clinical and histologic signs of disease and reduced the number of joints with severe damage.

CONCLUSION

Our results support the notion that the human epidermal growth factor receptor family has a role in the progression of collagen-induced arthritis. The novel tPA-herstatin fusion protein could be used as an effective therapeutic tool for control of inflammatory disorders involving an angiogenic component.

The role of resident synovial cells in destructive arthritis

Infiltration by inflammatory cells, thickening of the lining layer, and destructive invasion into cartilage and bone are pathognomic features of the synovium in rheumatoid arthritis (RA). However, the most common cell types at the sites of invasion are resident cells of the joint, in particular synovial fibroblasts. These cells differ from healthy synovial fibroblasts in their morphology, their expression of proto-oncogenes and antiapoptotic molecules, and in their lack of certain tumor suppressor genes. Through their production of proinflammatory cytokines and chemokines mediated by signaling via Toll-like receptors, they are not only effector cells but also active parts of the innate immune system attracting inflammatory immune cells to the synovium. Most importantly, by producing matrix-degrading molecules they contribute strongly to the destructive mechanisms operative in RA.

The TWEAK-Fn14 cytokine-receptor axis: discovery, biology and therapeutic targeting

TWEAK is a multifunctional cytokine that controls many cellular activities including proliferation, migration, differentiation, apoptosis, angiogenesis and inflammation. TWEAK acts by binding to Fn14, a highly inducible cell-surface receptor that is linked to several intracellular signalling pathways, including the nuclear factor-kappaB (NF-kappaB) pathway. The TWEAK-Fn14 axis normally regulates various physiological processes, in particular it seems to play an important, beneficial role in tissue repair following acute injury. Furthermore, recent studies have indicated that TWEAK-Fn14 axis signalling may contribute to cancer, chronic autoimmune diseases and acute ischaemic stroke. This Review provides an overview of TWEAK-Fn14 axis biology and summarizes the available data supporting the proposal that both TWEAK and Fn14 should be considered as potential targets for the development of novel therapeutics.

Direct binding of integrin alphavbeta3 to FGF1 plays a role in FGF1 signaling

Integrins play a role in fibroblast growth factor (FGF) signaling through cross-talk with FGF receptors (FGFRs), but the mechanism underlying the cross-talk is unknown. We discovered that FGF1 directly bound to soluble and cell-surface integrin alphavbeta3 (K(D) about 1 microm). Antagonists to alphavbeta3 (monoclonal antibody 7E3 and cyclic RGDfV) blocked this interaction. alphavbeta3 was the predominant, if not the only, integrin that bound to FGF1, because FGF1 bound only weakly to several beta1 integrins tested. We presented evidence that the CYDMKTTC sequence (the specificity loop) within the ligand-binding site of beta3 plays a role in FGF1 binding. We found that the integrin-binding site of FGF1 overlaps with the heparin-binding site but is distinct from the FGFR-binding site using docking simulation and mutagenesis. We identified an FGF1 mutant (R50E) that was defective in integrin binding but still bound to heparin and FGFR. R50E was defective in inducing DNA synthesis, cell proliferation, cell migration, and chemotaxis, suggesting that the direct integrin binding to FGF1 is critical for FGF signaling. Nevertheless, R50E induced phosphorylation of FGFR1 and FRS2alpha and activation of AKT and ERK1/2. These results suggest that the defect in R50E in FGF signaling is not in the initial activation of FGF signaling pathway components, but in the later steps in FGF signaling. We propose that R50E is a useful tool to identify the role of integrins in FGF signaling.

Anti-inflammatory effect of antidiabetic thiazolidinediones prevents bone resorption rather than cartilage changes in experimental polyarthritis

Background

Rosiglitazone and pioglitazone are high-affinity peroxisome proliferator-activated receptor (PPAR)-γ agonists with potent anti-diabetic properties and potential anti-inflammatory effects. We compared the ability of a range of oral doses of these thiazolidinediones, including those sufficient to restore insulin sensitization, to inhibit the pathogenesis of adjuvant-induced arthritis (AIA).

Methods

AIA was induced in Lewis rats by a subcutaneous injection of 1 mg of complete Freund's adjuvant. Rats were treated orally for 21 days with pioglitazone 3, 10 or 30 mg/kg/day, rosiglitazone 3 or 10 mg/kg/day, or with vehicle only. The time course of AIA was evaluated by biotelemetry to monitor body temperature and locomotor activity, by clinical score and plethysmographic measurement of hindpaw oedema. At necropsy, RT-PCR analysis was performed on synovium, liver and subcutaneous fat. Changes in cartilage were evaluated by histological examination of ankle joints, radiolabelled sulphate incorporation (proteoglycan synthesis), glycosaminoglycan content (proteoglycan turnover) and aggrecan expression in patellar cartilage. Whole-body bone mineral content was measured by dual-energy X-ray absorptiometry.

Results

The highest doses of rosiglitazone (10 mg/kg/day) or pioglitazone (30 mg/kg/day) were required to reduce fever peaks associated with acute or chronic inflammation, respectively, and to decrease arthritis severity. At these doses, thiazolidinediones reduced synovitis and synovial expression of TNF-α, IL-1β and basic fibroblast growth factor without affecting neovascularization or the expression of vascular endothelial growth factor. Thiazolidinediones failed to prevent cartilage lesions and arthritis-induced inhibition of proteoglycan synthesis, aggrecan mRNA level or glycosaminoglycan content in patellar cartilage, but reduced bone erosions and inflammatory bone loss. A trend towards lower urinary levels of deoxipyridinolin was also noted in arthritic rats treated with thiazolidinediones. Rosiglitazone 10 mg/kg/day or pioglitazone 30 mg/kg/day increased the expression of PPAR-γ and adiponectin in adipose tissue, confirming that they were activating PPAR-γ in inflammatory conditions, although an increase in fat mass percentage was observed for the most anti-arthritic dose.

Conclusion

These data emphasize that higher dosages of thiazolidinediones are required for the treatment of arthritis than for restoring insulin sensitivity but that thiazolidinediones prevent inflammatory bone loss despite exposing animals to increased fatness possibly resulting from excessive activation of PPAR-γ.

Photoacoustic tomography of carrageenan-induced arthritis in a rat model

Laser-based photoacoustic tomography (PAT), a novel, nonionizing, noninvasive, laser-based technology, has been adapted to the diagnosis and imaging of inflammatory arthritis. A commonly used adjuvant induced arthritis model using carrageenan was employed to simulate acute rheumatoid arthritis in rat tail joints. Cross-sectional photoacoustic images of joints affected by acute inflammation were compared to those of the control. The diameter of the periosteum and the optical absorption of intra-articular tissue were measured on each joint image. Significant differences were found on PAT imaging between the affected joints and the control for both variables measured, including enlarged periosteum diameter and enhanced intra-articular optical absorption occurring in the joints affected with carrageenan-induced arthritis. Anatomical correlation with histological sections of imaged joints and microMRI results verified the findings of PAT. This suggests that PAT has the potential for highly sensitive diagnosis and evaluation of pathologic hallmarks of acute inflammatory arthritis.

Developments in the synovial biology field 2006

Synovial pathophysiology is a complex and synergistic interplay of different cell populations with tissue components, mediated by a variety of signaling mechanisms. All of these mechanisms drive the affected joint into inflammation and drive the subsequent destruction of cartilage and bone. Each cell type contributes significantly to the initiation and perpetuation of this deleterious concert, especially in rheumatoid arthritis. Rheumatoid arthritis synovial fibroblasts and macrophages, both cell types with pivotal roles in inflammation and destruction, but also T cells and B cells are crucial for complex network in the inflamed synovium. An even more complex cellular crosstalk between these key players maintains a process of chronic inflammation. As outlined in the present review, in the past year substantial progress has been made to elucidate further details of the rich pathophysiology of rheumatoid arthritis, which may also facilitate the identification of novel targets for future therapeutic strategies.

Evolving functions of endothelial cells in inflammation

Inflammation is usually analysed from the perspective of tissue-infiltrating leukocytes. Microvascular endothelial cells at a site of inflammation are both active participants in and regulators of inflammatory processes. The properties of endothelial cells change during the transition from acute to chronic inflammation and during the transition from innate to adaptive immunity. Mediators that act on endothelial cells also act on leukocytes and vice versa. Consequently, many anti-inflammatory therapies influence the behaviour of endothelial cells and vascular therapeutics influence inflammation. This Review describes the functions performed by endothelial cells at each stage of the inflammatory process, emphasizing the principal mediators and signalling pathways involved and the therapeutic implications.

The role of vascular cell adhesion molecule 1/ very late activation antigen 4 in endothelial progenitor cell recruitment to rheumatoid arthritis synovium

OBJECTIVE

Marrow-derived endothelial progenitor cells (EPCs) are important in the neovascularization that occurs in diverse conditions such as cardiovascular disorders, inflammatory diseases, and neoplasms. In rheumatoid arthritis (RA), synovial neovascularization propels disease by nourishing the inflamed and hyperproliferative synovium. This study was undertaken to investigate the hypothesis that EPCs selectively home to inflamed joint tissue and may perpetuate synovial neovascularization.

METHODS

In a collagen-induced arthritis (CIA) model, neovascularization and EPC accumulation in mouse ankle synovium was measured. In an antibody-induced arthritis model, EPC recruitment to inflamed synovium was evaluated. In a chimeric SCID mouse/human synovial tissue (ST) model, mice were engrafted subcutaneously with human ST, and EPC homing to grafts was assessed 2 days later. EPC adhesion to RA fibroblasts and RA ST was evaluated in vitro.

RESULTS

In mice with CIA, cells bearing EPC markers were significantly increased in peripheral blood and accumulated in inflamed synovial pannus. EPCs were 4-fold more numerous in inflamed synovium from mice with anti-type II collagen antibody-induced arthritis versus controls. In SCID mice, EPC homing to RA ST was 3-fold greater than to normal synovium. Antibody neutralization of vascular cell adhesion molecule 1 (VCAM-1) and its ligand component alpha4 integrin potently inhibited EPC adhesion to RA fibroblasts and RA ST cryosections.

CONCLUSION

These data demonstrate the selective recruitment of EPCs to inflamed joint tissue. The VCAM-1/very late activation antigen 4 adhesive system critically mediates EPC adhesion to cultured RA fibroblasts and to RA ST cryosections. These findings provide evidence of a possible role of EPCs in the synovial neovascularization that is critical to RA pathogenesis.

Cytokines in the pathogenesis of rheumatoid arthritis

Cytokines regulate a broad range of inflammatory processes that are implicated in the pathogenesis of rheumatoid arthritis. In rheumatoid joints, it is well known that an imbalance between pro- and anti-inflammatory cytokine activities favours the induction of autoimmunity, chronic inflammation and thereby joint damage. However, it remains less clear how cytokines are organized within a hierarchical regulatory network, and therefore which cytokines may be the best targets for clinical intervention a priori. Here, we discuss the crucial effector function of cytokines in the immunological processes that are central to the pathogenesis of rheumatoid arthritis.

Angiogenesis markers (VEGF, soluble receptor of VEGF and angiopoietin-1) in very early arthritis and their association with inflammation and joint destruction

OBJECTIVE

To investigate the involvement of angiogenesis markers in very early arthritis patients and their relevance to predict further joint destruction.

METHODS

Levels of Vascular Endothelial Growth Factor (VEGF), angiopoietin-1 (Ang-1), and soluble Fms-like tyrosine kinase-1 (sFlt-1) were measured by ELISA in serum samples from 310 patients having polyarthritis, evolving for less than 6 months (VErA cohort). Each angiogenesis marker was measured at baseline and one year later. X-rays of hands and feet were carried out at inclusion and after 1 year and read using the van der Heidje-modified Sharp method.

RESULTS

At baseline and after 1 year, VEGF levels were correlated with clinical and biological parameters of inflammation. We also observed a positive correlation between sFlt-1 levels and biological inflammation (Erythrocyte Sedimentation Rate (ESR): r=0.17, p=0.006; C Reactive Protein: r=0.14, p=0.02). Angiopoietin-1 levels were correlated with ESR (r=0.12, p=0.04). Interestingly, only VEGF levels measured at baseline were correlated with Disease Activity Score measured 1 year later. Relationship between angiogenesis markers and radiographic progression was also evaluated. VEGF and Ang-1 levels measured at inclusion were related with Sharp score after one year (VEGF: r=0.21, p<0.001; Ang-1: r=0.24, p<0.001; Spearman's test). Moreover, VEGF levels were higher in patients with radiographic progression (p=0.002).

CONCLUSION

Serum concentrations of VEGF, sFlt-1 and angiopoietin-1 were correlated to parameters of inflammation and to bone destruction in early arthritis. These results contribute to demonstrate that angiogenesis reflects disease severity and angiogenesis markers might become a new useful tool to evaluate disease activity and to estimate outcome for patients with inflammatory arthritis.

Differential expression of syndecans and glypicans in chronically inflamed synovium

BACKGROUND

Membrane-bound heparan sulphate proteoglycans (HSPGs) act as co-receptors and presenters of cytokines and are involved in cell-matrix and cell-cell adhesion.

AIM

To investigate which HSPGs are expressed in knee joint synovia from patients with different forms of arthritis and normal individuals.

METHODS

Synovial samples were obtained from patients with early rheumatoid arthritis (n = 8), longstanding rheumatoid arthritis (n = 13), psoriatic arthritis (n = 7), osteoarthritis (n = 6) and normal joints (n = 12). Expression of syndecan-1, -2, -3 and -4 and glypican-1, -3 and -4 was analysed by immunohistochemistry and dual label immunofluorescence.

RESULTS

The expression of HSPGs in chronically inflamed synovium exhibited a differential distribution. Syndecan-1 was present in the mononuclear infiltrates of synovia from patients with rheumatoid and psoriatic arthritis where it was expressed by plasma cells. Syndecan-2 was present mainly in blood vessels where it occurred on endothelial cells, pericytes and smooth muscle cells. Syndecan-3 stained intensely in endothelial cells but also occurred in sublining macrophages and the lining layer. Glypican-4 occurred in the lining layer and blood vessels. Increased expression of these HSPGs was apparent in rheumatoid and psoriatic compared to osteoarthritic and normal synovia. Little or no staining for syndecan-4, glypican-1 and glypican-3 was seen in all samples.

DISCUSSION

Selected HSPGs, such as syndecan-1, -2 and -3 and glypican-4, could play a part in the pathophysiology of arthritis, such as the migration and retention of leukocytes and angiogenesis in the chronically inflamed synovium.

Bevacizumab in the management of solid tumors

Angiogenesis is defined as the formation of new blood vessels from a pre-existing vascular bed. By supplying nutrients and oxygen and removing waste products in malignant tumors, it is an essential process that regulates cancer growth and dissemination. This process is regulated by both pro- and antiangiogenic compounds. Vascular endothelial growth factor is one of the most important and best-studied proangiogenic factors. Bevacizumab, a monoclonal antibody against vascular endothelial growth factor, has been shown to inhibit angiogenesis and is proving to be of clinical benefit in a variety of tumor types. The strongest evidence comes from studies in advanced colorectal and non-small-cell lung cancer, with growing evidence in breast and epithelial ovarian tumors. The duration and timing of bevacizumab's use is currently the focus of several ongoing clinical trials.

[Angiogenesis. Possibilities for therapeutic intervention in rheumatic diseases]

In contrast to vasculogenesis, angiogenesis is defined as the formation of new vessels from preexisting ones. Physiologically, this multistep process occurs in adults during the reproductive cycle and during pregnancy, pathophysiologically it can be found in wound healing, inflammation and carcinogenesis. The underlying mechanisms are vasodilatation and increasing permeability, destabilization of vessel walls and degradation of extracellular matrix, followed by the proliferation and migration of endothelial cells. Migrated endothelial cells form vascular tubes at sites of ischemia and these tubes are finally stabilized by pericytes and smooth muscle cells. This process is controlled by a complex interaction of angiogenic and angiostatic factors. In contrast to carcinogenesis, the role of angiogenesis for the pathogenesis and therapy of rheumatic diseases is less understood. Two examples for pathologically disturbed angiogenesis, rheumatoid arthritis and systemic sclerosis, are discussed in this review with respect to therapeutic options.

Angiogenesis and chronic inflammation: cause or consequence?

Evidence has been gathered regarding the association between angiogenesis and inflammation in pathological situations. These two phenomena have long been coupled together in many chronic inflammatory disorders with distinct etiopathogenic origin, including psoriasis, rheumatoid arthritis, Crohn's disease, diabetes, and cancer. Lately, this concept has further been substantiated by the finding that several previously established non-inflammatory disorders, such as osteoarthritis and obesity, display both inflammation and angiogenesis in an exacerbated manner. In addition, the interplay between inflammatory cells, endothelial cells and fibroblasts in chronic inflammation sites, together with the fact that inflammation and angiogenesis can actually be triggered by the same molecular events, further strengthen this association. Therefore, elucidating the underlying cellular and molecular mechanisms that gather together the two processes is mandatory in order to understand their synergistic effect, and to develop new therapeutic approaches for the management of these disorders that cause a great deal of discomfort, disability, and in some cases death.

Amelioration of collagen-induced arthritis in rats by nanogold

OBJECTIVE

Angiogenesis plays a part in the pathogenesis of rheumatoid arthritis (RA), and nanogold inhibits the activity of an angiogenic factor, vascular endothelial growth factor (VEGF). We therefore investigated whether intraarticular delivery of nanogold ameliorates collagen-induced arthritis (CIA) in rats.

METHODS

Binding of 13-nm nanogold to VEGF in human RA synovial fluid (SF) and its effects on RA SF-induced endothelial cell proliferation and migration were assessed. Nanogold was administered intraarticularly to rats with CIA before the onset of arthritis. Progression of CIA was monitored by measures of clinical, radiologic, and histologic changes. In addition, the microvessel density and extent of infiltrating macrophages as well as levels of tumor necrosis factor alpha (TNFalpha) and interleukin-1beta (IL-1beta) in the ankle joints were determined.

RESULTS

Nanogold bound to VEGF in RA SF, resulting in inhibition of RA SF-induced endothelial cell proliferation and migration. Significant reductions in ankle circumference, articular index scores, and radiographic scores were observed in the nanogold-treated rats with CIA compared with their control counterparts. In addition, the histologic score (of synovial hyperplasia, cartilage erosion, and leukocyte infiltration), microvessel density, macrophage infiltration, and levels of TNFalpha and IL-1beta were also significantly reduced in the ankle joints of nanogold-treated rats.

CONCLUSION

Our results are the first to demonstrate that intraarticular administration of nanogold ameliorates the clinical course of CIA in rats. Nanogold exerted antiangiogenic activities and subsequently reduced macrophage infiltration and inflammation, which resulted in attenuation of arthritis. These results demonstrate proof of principle for the use of nanogold as a novel therapeutic agent for the treatment of RA.

Vascular Endothelial Growth Factor (VEGF) in Autoimmune Diseases

Vascular endothelial growth factor (VEGF) is a potent stimulating factor for angiogenesis and vascular permeability. There are eight isoforms with different and sometimes overlapping functions. The mechanisms of action are under investigation with emerging insights into overlapping pathways and cross-talk between other receptors such as the neuropilins, which were not previously associated to angiogenesis. VEGF has important physiological actions on embryonic development, healing, and menstrual cycle. It also has a great role in pathological conditions that are associated to autoimmune diseases. There is considerable evidence in various autoimmune diseases such as in systemic lupus erythematosus, rheumatoid arthritis, and multiple sclerosis of an interrelationship between the VEGF system and theses disorders. Serum levels of VEGF correlate with disease activity in a large number of autoimmune diseases and fall with the use of standard therapy. We raised the possible future therapeutic strategies in autoimmune diseases with the anti-VEGF or anti-VEGFR (receptor). So far, this therapy has been used in cancer and macular ocular degeneration in diabetes. This review outlines the evidence for VEGF participation in various autoimmune diseases and proposes lines for future research in this field.

Growth hormone, VEGF and FGF: involvement in rheumatoid arthritis

Adult rheumatoid arthritis (RA), a systemic autoimmune disorder of unknown etiology, is characterized by dysfunctional cellular and humoral immunity, enhanced migration and attachment of peripheral macrophages and pro-inflammatory leukocytes to the synovium and articular cartilage of diarthrodial joints. The progressive destruction of cartilage and bone in RA is a result of elevated pro-inflammatory cytokine gene expression, synovial neovascularization, proteinase-mediated dissolution of articular cartilage matrix and osteoclast-mediated subchondral bone resorption. Juvenile chronic arthritis (JCA) is disease with manifestations similar to adult RA that occurs in childhood. JCA usually causes precocious joint destruction and often also presents with evidence of growth plate anomalies and reduced stature. Three proteins play an integral role in both adult RA and JCA. These are somatotropin (also called pituitary growth hormone (GH)), vascular endothelial growth factor (VEGF) and fibroblast growth factor (FGF). GH is responsible for regulating long bone growth and skeletal maturation through its capacity to stimulate insulin-like growth factor-I (IGF-1) synthesis by hepatocytes. Mechanisms responsible for growth plate disturbances and short stature in children with JCA include deficient GH production, GH-insensitivity resulting from defects in the GH receptor, suppressed IGF-1 synthesis or neutralization of IGF-1 action by IGF-1 binding proteins (IGFBPs). In addition, GH has also been implicated in perpetuating inflammation and pain in adult RA. VEGF has been shown to be the critical angiogenesis factor responsible for vascular proliferation and blood vessel invasion of the synovial lining membrane in RA. Acidic FGF (FGF-1) and basic FGF (FGF-2) have also been implicated in aberrant synoviocyte proliferation (i.e. synovial hyperplasia) and apoptosis resistance in adult RA.

Power Doppler ultrasonography and synovitis: correlating ultrasound imaging with histopathological findings and evaluating the performance of ultrasound equipments

OBJECTIVES

To examine the validity of power Doppler ultrasound imaging to identify synovitis, using histopathology as gold standard, and to assess the performance of ultrasound equipments.

METHODS

44 synovial sites in small and large joints, bursae and tendon sheaths were depicted with ultrasound. A synovial biopsy was performed on the site depicted and a synovial sample was taken for histopathological evaluation. The performance of three ultrasound devices was tested using flow phantoms.

RESULTS

A positive Doppler signal was detected in 29 of 35 (83%) of the patients with active histological inflammation. In eight additional samples, histological examination showed other pathological synovial findings and a Doppler signal was detected in five of them. No significant correlation was found between the amount of Doppler signal and histological synovitis score (r = 0.239, p = NS). The amount of subsynovial infiltration of polymorphonuclear leucocytes and surface fibrin correlated significantly with the amount of power Doppler signal: r = 0.397 (p<0.01) and 0.328 (p<0.05), respectively. The ultrasound devices differed in showing the smallest detectable flow.

CONCLUSIONS

A negative Doppler signal does not exclude the possibility of synovitis. A positive Doppler signal in the synovium is an indicator of an active synovial inflammation in patients. A Doppler signal does not correlate with the extent of the inflammation and it can also be seen in other synovial reactions. It is important that the quality measurements of ultrasound devices are reported, because the results should be evaluated against the quality of the device used.

Pathomechanisms in rheumatoid arthritis--time for a string theory?

RA is a quintessential autoimmune disease with a growing number of cells, mediators, and pathways implicated in this tissue-injurious inflammation. Now Kuhn and colleagues have provided convincing evidence that autoantibodies reacting with citrullinated proteins, known for their sensitivity and specificity as biomarkers in RA, enhance tissue damage in collagen-induced arthritis (see the related article beginning on page 961). This study adds yet another soldier to the growing army of autoaggressive mechanisms that underlie RA. With great success researchers have dismantled the pathogenic subunits of RA, adding gene to gene, molecule to molecule, and pathway to pathway in an ever more complex scheme of dysfunction. The complexity of the emerging disease model leaves us speechless. It seems that with this wealth of data available, we need to develop a new theory for this disease. We may want to seek guidance from our colleagues in physics and mathematics who have successfully integrated their knowledge of elementary particles and the complexity of their interacting forces by formulating the string theory.

Targeting rheumatoid tenosynovial angiogenesis with cytokine inhibitors

Proliferation and invasion of the tenosynovial lining of tendons in patients with rheumatoid arthritis can result in tendon damage and rupture, leading to decreased hand function. Angiogenesis is an important process in rheumatoid joint disease; however, the role of angiogenesis in tendon disease is unknown. Our aim was to determine whether rheumatoid tenosynovial lining could produce angiogenic proteins, and if inhibition of tumor necrosis factor-alpha and interleukin-1 could decrease vascular endothelial growth factor production. Samples of encapsulating and invasive tenosynovial lining taken from the same hand and wrist synovial lining were harvested from 58 patients with rheumatoid arthritis having wrist surgery. Ex vivo samples were studied to quantify vascularity, angiogenic protein production under normoxic and hypoxic conditions, and the effect of inhibiting tumor necrosis factor-alpha and interleukin-1 on vascular endothelial growth factor production. Rheumatoid tenosynovial lining was more vascular than rheumatoid joint synovial lining and produced high levels of angiogenic factors such as vascular endothelial growth factor, interleukin-1beta, fibroblast growth factor-2, and angiopoietin-2. Hypoxia induced an increase in production of vascular endothelial growth factor by ex vivo tenosynovial lining cells. Inhibition of the cytokines interleukin-1 and tumor necrosis factor-alpha effectively reduced vascular endothelial growth factor production by tenosynovial samples.

LEVEL OF EVIDENCE

Therapeutic study. Level II (Prospective comparative study). See the Guidelines for Authors for a complete description of levels of evidence.

VEGF gene expression is regulated post-transcriptionally in macrophages

The macrophage is critical to the innate immune response and contributes to human diseases, including inflammatory arthritis and plaque formation in atherosclerosis. Vascular endothelial growth factor (VEGF) is an angiogenic cytokine that is produced by macrophages. To study the regulation of VEGF production in macrophages we show that stimulation of monocyte-macrophage-like RAW-264.7 cells by lipopolysaccharide (LPS) increases expression of VEGF mRNA and protein. Three alternative splicing VEGF mRNA isoforms are produced, and the stability of VEGF mRNA increases following cellular activation. To study post-transcriptional regulation of the VEGF gene the 3'-untranslated region (3' UTR) was introduced into the 3' UTR of the luciferase gene in a reporter construct. In both RAW-264.7 cells and thioglycollate-elicited macrophages, the 3' UTR sequence dramatically reduces reporter expression. Treatment with activators of macrophages, including LPS, lipoteichoic acid, and VEGF protein, stimulates expression of 3' UTR reporters. Finally, mapping studies of the 3' UTR of VEGF mRNA show that deletion of the heterogeneous nuclear ribonucleoprotein l binding site affects basal reporter expression in RAW-264.7 cells, but does not affect reporter activation with LPS. Together these results demonstrate that a post-transcriptional mechanism contributes to VEGF gene expression in activated macrophage cells.

Ultrasmall supraparamagnetic iron oxide-enhanced magnetic resonance imaging of antigen-induced arthritis: a comparative study between SHU 555 C, ferumoxtran-10, and ferumoxytol

OBJECTIVES

We sought to compare the ability of 3 ultrasmall superparamagnetic iron oxides (USPIOs) to detect and characterize antigen-induced arthritis with MR imaging.

MATERIALS AND METHODS

A monoarthritis was induced in the right knee of 18 rats. The left knee served as a normal control. Knees underwent magnetic resonance (MR) imaging before, up to 2 hours, and 24 hours after injection (p.i.) of 200 mumol Fe/kg SHU 555 C (n= 6), ferumoxtran-10 (n = 6), or ferumoxytol (n = 6), using T2-2D-SE 100/20,40,60,80/90 (TR/TE/flipangle), T2*-3D-spoiled gradient recalled (SPGR) 100/15/38, and T1-3D-SPGR 50/1,7/60 sequences.

RESULTS

Quantitative signal to noise ratio and DeltaSI data of arthritic knees on T1- and T2*-weighted MR images showed no significant differences between the 3 USPIOs (P > 0.05). At 2 hours p.i., SNR and DeltaSI data were significantly increased from baseline on T1-weighted images and significantly decreased on T2*-weighted images (P < 0.001). At 24 hours p.i., the T1-enhancement returned to baseline, whereas the T2*-enhancement remained significantly elevated (P < 0.001). Immunostains demonstrated an USPIO compartmentalization in macrophages in the arthritic synovium.

CONCLUSIONS

Based on the relatively small number of animals in our study group, inflammation in antigen-induced arthritis can be equally detected and characterized with any of the three USPIOs evaluated.

Angiogenesis--a new target for future therapy

Development of blood vessels from in situ differentiating endothelial cells (EC) is called vasculogenesis, whereas sprouting of new blood vessels from the pre-existing ones is termed angiogenesis or neovascularisation. Angiogenesis, the growth of new blood vessels, is essential during tissue repair, foetal development, and female reproductive cycle. In contrast, uncontrolled angiogenesis promotes tumor and retinopathies, while inadequate angiogenesis can lead to coronary artery disease. A balance between pro-angiogenic and anti-angiogenic growth factors and cytokines tightly controls angiogenesis. With the identification of several proangiogenic molecules such as the vascular endothelial cell growth factor (VEGF), the fibroblast growth factors (FGFs), and the angiopoietins, and the recent description of specific inhibitors of angiogenesis such as platelet factor-4, angiostatin, endostatin, and vasostatin, it is recognized that therapeutic interference with vasculature formation offers a tool for clinical applications in various pathologies. Inhibition of angiogenesis can prevent diseases such as cancer, diabetic nephropathy, arthritis, psoriasis, whereas stimulation of angiogenesis is beneficial in the treatment of coronary artery disease (CAD), cardiac failure, tissue injury, etc. One of the most specific and critical regulators of angiogenesis is vascular endothelial growth factor (VEGF), which regulates endothelial proliferation, permeability, and survival. Substantial evidence also implicates VEGF as an angiogenic mediator in tumors and intraocular neovascular syndromes, and numerous clinical trials are presently testing the hypothesis that inhibition of VEGF may have therapeutic value.

Angiogenic and cell survival functions of vascular endothelial growth factor (VEGF)

Vascular endothelial growth factor (VEGF) was originally identified as an endothelial cell specific growth factor stimulating angiogenesis and vascular permeability. Some family members, VEGF C and D, are specifically involved in lymphangiogenesis. It now appears that VEGF also has autocrine functions acting as a survival factor for tumour cells protecting them from stresses such as hypoxia, chemotherapy and radiotherapy. The mechanisms of action of VEGF are still being investigated with emerging insights into overlapping pathways and cross-talk between other receptors such as the neuropilins which were not previously associated with angiogenesis. VEGF plays an important role in embryonic development and angiogenesis during wound healing and menstrual cycle in the healthy adult. VEGF is also important in a number of both malignant and non-malignant pathologies. As it plays a limited role in normal human physiology, VEGF is an attractive therapeutic target in diseases where VEGF plays a key role. It was originally thought that in pathological conditions such as cancer, VEGF functioned solely as an angiogenic factor, stimulating new vessel formation and increasing vascular permeability. It has since emerged it plays a multifunctional role where it can also have autocrine pro-survival effects and contribute to tumour cell chemoresistance. In this review we discuss the established role of VEGF in angiogenesis and the underlying mechanisms. We discuss its role as a survival factor and mechanisms whereby angiogenesis inhibition improves efficacy of chemotherapy regimes. Finally, we discuss the therapeutic implications of targeting angiogenesis and VEGF receptors, particularly in cancer therapy.

Synovial vascular patterns and angiogenic factors expression in synovial tissue and serum of patients with rheumatoid arthritis

OBJECTIVE

To determine whether subgroups of rheumatoid arthritis (RA) patients classified according to their synovial vascular pattern have a different expression of angiogenic mediators or exhibit distinct clinical or biological characteristics.

METHODS

Arthroscopies were performed in 27 patients with RA and synovial samples were obtained. Vascular morphology was classified in three patterns: straight (S), tortuous (T) and mixed (M). Immunostaining was performed with anti-vascular endothelial growth factor (anti-VEGF), anti-vascular endothelial growth factor receptor (VEGFR)-1, anti-VEGFR-2, anti-IL-8 and anti-TGF-beta, and measured by digital image analysis. Serum levels of VEGF, TGF-beta and IL-8, and clinical, radiographic and serological data were also analysed.

RESULTS

Eleven (41%) patients had the S pattern, nine (33%) the M pattern and seven (26%) the T pattern. The S and M groups had a higher prevalence of rheumatoid factor positivity and erosive disease, and higher levels of markers of systemic inflammation compared with the T group. Synovial expression of VEGF was higher in the S and T groups compared with the M group, whereas TGF-beta was higher in the T compared with the S and M groups. Distinct synovial distribution of VEGF and TGF-beta between groups was also observed.

CONCLUSIONS

This preliminary study suggests that RA patients with the S and M patterns share different clinical, biological and serological characteristics compared with those with the T pattern, which may constitute a group with less severe disease. Differences in the intensity and distribution of synovial expression of VEGF and TGF-beta observed between groups could have pathophysiological relevance. However, larger, prospective multicentre studies would be need to determine the clinical relevance of vascular patterns in RA.

Functional inhibition of NF-kappaB signal transduction in alphavbeta3 integrin expressing endothelial cells by using RGD-PEG-modified adenovirus with a mutant IkappaB gene

In order to selectively block nuclear factor κB (NF-κB)-dependent signal transduction in angiogenic endothelial cells, we constructed an αvβ3 integrin specific adenovirus encoding dominant negative IκB (dnIκB) as a therapeutic gene. By virtue of RGD modification of the PEGylated virus, the specificity of the cell entry pathway of adenovirus shifted from coxsacki-adenovirus receptor dependent to αvβ3 integrin dependent entry. The therapeutic outcome of delivery of the transgene into endothelial cells was determined by analysis of cellular responsiveness to tumor necrosis factor (TNF)-α. Using real time reverse transcription PCR, mRNA levels of the cell adhesion molecules E-selectin, vascular cell adhesion molecule (VCAM)-1 and intercellular adhesion molecule (ICAM)-1, the cytokines/growth factors IL-6, IL-8 and vascular endothelial growth factor (VEGF)-A, and the receptor tyrosine kinase Tie-2 were assessed. Furthermore, levels of ICAM-1 protein were determined by flow cytometric analysis. RGD-targeted adenovirus delivered the dnIκB via αvβ3 to become functionally expressed, leading to complete abolishment of TNF-α-induced up-regulation of E-selectin, ICAM-1, VCAM-1, IL-6, IL-8, VEGF-A and Tie-2. The approach of targeted delivery of dnIκB into endothelial cells presented here can be employed for diseases such as rheumatoid arthritis and inflammatory bowel disease where activation of NF-κB activity should be locally restored to basal levels in the endothelium.

Transdermal photodynamic therapy—a treatment option for rheumatic destruction of small joints?

BACKGROUND AND OBJECTIVE

Synovectomy of small joints is a therapeutic approach in patients suffering from rheumatoid arthritis (RA). We examined the feasibility of transdermal photodynamic therapy (tPDT) in a fibroblast-induced model of joint destruction using the novel photosensitizer (PS) tetrahydroporphyrin-tetratosylat that shows strong absorption at the near infra-red spectral region.

MATERIALS AND METHODS

The functionality of the PDT system was assessed in vitro. Following arthritis induction and PS application, tPDT was applied in vivo. Therapy results were evaluated by measuring joint swelling, serum amyloid A (SAA) and histologically.

RESULTS

We were able to present a fully functional PDT in vitro. The in vivo therapy modalities were well tolerated by mice. We could demonstrate photodynamic ablation of subcutaneously located tissue (skeletal muscle) without skin damage.

CONCLUSION

This study provides the basis for transdermal accessibility of tissue through a photodynamic process which may serve as a minimally invasive synovectomy strategy.

The anti-angiogenic effect of sinomenine

Sinomenine is an alkaloid extracted from the Chinese medicinal plant, Sinomenium acutum, which has been utilized to treat rheumatoid arthritis (RA) in China for over 2000 years. Sinomenine has been shown to mediate a wide range of pharmacological actions which includes anti-inflammatory and anti-rheumatic effects. RA has been classified as a chronic immune-mediated disease that exhibits overlapping manifestation of inflammatory, abnormal cellular and hormonal immune responses with synovial hyperplasia. Since, angiogenesis is recognized to play a critical role in the development of RA and anti-angiogenic therapy has been proposed as a new therapeutic strategy for treatment of RA, we would like to see if sinomenine possesses anti-angiogenic property. In this study, sinomenine inhibited bFGF-induced proliferation of human umbilical vein endothelial cells (HUVEC) and arrested its cell cycle in G1 phase. Sinomenine disrupted tube formation of HUVEC on Matrigel and suppressed the chemotaxis of HUVEC. In addition, sinomenine reduced neovascularization in Matrigel plug assay as well as microvascular outgrowth in rat aorta ring sprouting assay. These results suggest that sinomenine inhibited bFGF-induced angiogenesis in vitro and in vivo. As the leukocytes-endothelial adhesive interactions also play an important role in inflammation, we found that sinomenine reduced the transmigration of granulocytic differentiated HL60 cells across IL-1beta activated HUVEC monolayer. Therefore, the inhibition of leukocytes migration across blood vessel walls and the anti-angiogenic effect of sinomenine may contribute towards its therapeutic mechanisms in alleviating the pathogenesis of RA.

Elucidation of the mechanisms underlying the angiogenic effects of ginsenoside Rg(1) in vivo and in vitro

The major active constituents of ginseng are ginsenosides, and Rg(1) is a predominant compound of the total extract. Recent studies have demonstrated that Rg(1) can promote angiogenesis in vivo and in vitro. In this study, we used a DNA microarray technology to elucidate the mechanisms of action of Rg(1). We report that Rg(1) induces the proliferation of HUVECs, monitored using [(3)H]-thymidine incorporation and Trypan blue exclusion assays. Furthermore, Rg(1) (150-600 nM) also showed an enhanced tube forming inducing effect on the HUVEC. Rg(1) was also demonstrated to promote angiogenesis in an in vivo Matrigel plug assay, and increase endothelial sprouting in the ex vivo rat aorta ring assay. Differential gene expression profile of HUVEC following treatment with Rg(1) revealed the expression of genes related to cell adhesion, migration and cytoskeleton, including RhoA, RhoB, IQGAP1, CALM2, Vav2 and LAMA4. Our results suggest that Rg(1) can promote angiogenesis in multiple models, and this effect is partly due to the modulation of genes that are involved in the cytoskeletal dynamics, cell-cell adhesion and migration.

Rheumatoid disease and ischaemic heart disease: Insights from pathophysiology and vascular biology

Rheumatoid disease (RD) is a multisystem inflammatory disorder, which is associated with an increased cardiovascular mortality, thought to be due to ischaemic heart disease (IHD). The precise mechanisms causing increased IHD in RD are unclear. However, there is increasing recognition that atherosclerosis is another chronic inflammatory condition, which shares several pathophysiological features with RD. For example, endothelial damage/dysfunction, platelet activation, hypercoagulability and angiogenesis are well-recognised in both disease processes. Furthermore, RD may influence traditional risk factors such as dyslipidaemia. Although the exact reasons for the increased ischaemic burden are unclear, physicians should place a high priority upon reducing cardiovascular risk in sufferers of RD. This review summarises factors that might contribute to the pathogenesis of IHD in RD. Discussion will focus upon features shared by atherosclerotic and rheumatoid processes, as well as possible interactions between RD and conventional IHD risk factors.

Expression of ADAM15 in rheumatoid synovium: up-regulation by vascular endothelial growth factor and possible implications for angiogenesis

ADAMs (a disintegrin and metalloproteinases) comprise a new gene family of metalloproteinases, and may play roles in cell-cell interaction, cell migration, signal transduction, shedding of membrane-anchored proteins and degradation of extracellular matrix. We screened the mRNA expression of 10 different ADAMs with a putative metalloproteinase motif in synovial tissues from patients with rheumatoid arthritis (RA) or osteoarthritis (OA). Reverse transcription PCR and real-time quantitative PCR analyses indicated that among the ADAMs, ADAM15 mRNA was more frequently expressed in the RA samples and its expression level was significantly 3.8-fold higher in RA than in OA (p < 0.01). In situ hybridization, immunohistochemistry and immunoblotting demonstrated that ADAM15 is expressed in active and precursor forms in the synovial lining cells, endothelial cells of blood vessels and macrophage-like cells in the sublining layer of RA synovium. There was a direct correlation between ADAM15 mRNA expression levels and vascular density in the synovial tissues (r = 0.907, p < 0.001; n = 20). ADAM15 was constitutively expressed in RA synovial fibroblasts and human umbilical vein endothelial cells (HUVECs), and the expression level was increased in HUVECs by treatment with vascular endothelial growth factor (VEGF)165. On the other hand, ADAM15 expression in RA synovial fibroblasts was enhanced with VEGF165 only if vascular endothelial growth factor receptor (VEGFR)-2 expression was induced by treatment with tumor necrosis factor-alpha, and the expression was blocked with SU1498, a specific inhibitor of VEGFR-2. These data demonstrate that ADAM15 is overexpressed in RA synovium and its expression is up-regulated by the action of VEGF165 through VEGFR-2, and suggest the possibility that ADAM15 is involved in angiogenesis in RA synovium.

Analysis of vascular endothelial growth factor (VEGF) functional variants in rheumatoid arthritis

The vascular endothelial growth factor (VEGF) is one of the most important pro-angiogenic mediators related to inflammation-associated synovial angiogenesis. The aim of this study was to asses the role of -1154 G-->A (rs1570360) and -634 G-->C (rs2010963) VEGF gene functional variants with rheumatoid arthritis (RA). The population under study was composed of a total of 753 unrelated RA patients and 801 healthy controls. The VEGF -1154 G-->A and -634 G-->C polymorphism genotyping was performed by real-time polymerase chain reaction technology, using TaqMan 5' allelic discrimination assay. No evidence of association was observed between the -1154 G-->A and the -634 G-->C VEGF polymorphisms, or inferred VEGF haplotypes with RA susceptibility or clinical manifestations. Our results suggest that the analyzed VEGF promoter polymorphisms may not play a relevant role in RA pathogenesis in our population.

Influence of VEGF gene polymorphisms on the severity of ankylosing spondylitis

OBJECTIVES

To investigate the role of polymorphisms of the vascular endothelial growth factor (VEGF) gene in susceptibility to ankylosing spondylitis (AS), and their relationship to clinical features and radiographic severity.

METHODS

This study included 157 patients with AS and 140 healthy unrelated controls. Polymorphisms of the VEGF gene were analysed by the polymerase chain reaction (PCR)-restriction fragment length polymorphism assay and amplification refractory mutation system-PCR. Haplotypes were reconstructed using the Bayesian algorithm. Radiographic severity was assessed by the Bath Ankylosing Spondylitis Radiological Index (BASRI).

RESULTS

The genotype frequencies of the polymorphisms were in Hardy-Weinberg equilibrium. The distributions of genotypes and alleles did not differ between AS patients and controls. Among the six haplotypes reconstructed based on the tight linkage disequilibrium at positions -2578, -1154 and -634 (pairwise linkage disequilibrium coefficient, r = 0.361-0.706), no haplotype was associated with susceptibility to AS. Clinical features were analysed for the four haplotypes (CGC, CGG, AAG, AGG) which were prevalent. In carriers of the AGG haplotype, the frequency of cervical spine involvement was significantly higher (P = 0.002, P(corr) = 0.036) and that of patients showing a BASRI score >6 was also higher (P = 0.025, P(corr) = 0.45).

CONCLUSIONS

This study demonstrates that polymorphisms of the VEGF gene may contribute to disease severity in AS.

Biological activity of bevacizumab, a humanized anti-VEGF antibody in vitro

Bevacizumab (Avastin, Genentech) is a humanized monoclonal antibody targeting vascular endothelial growth factor (VEGF), a critical angiogenic factor involved in both physiological and pathological conditions. It has been recently approved by the US FDA as a first-line therapy for widespread metastatic colorectal cancer. This report is a detailed biological characterization of bevacizumab in a variety of in vitro models. It is shown that bevacizumab potently neutralizes VEGF and blocks its signal transduction through both the VEGFR-1 and VEGFR-2 receptors, as demonstrated by the inhibition of VEGF-induced cell proliferation, survival, permeability, nitric oxide production, as well as migration and tissue factor production. Although bevacizumab retains the ability to bind to human Fcgamma receptors and complement protein C1q, it does not demonstrate cell or complement-mediated cytotoxicity in either VEGF producing or targeting cells. Thus the mechanism of anti-tumor activity of bevacizumab is most likely due to its anti-angiogenesis effect through binding and neutralization of secreted VEGF.

Adenosine receptors and the control of endothelial cell function in inflammatory disease

The nucleoside adenosine accumulates in many tissues following the onset of ischaemia and inflammation. This initiates a series of protective mechanisms in target cells upon binding and activation of a family of four G-protein-coupled cell surface adenosine receptor (AR) proteins. The magnitude and duration of adenosine's effects are dictated by the identity and expression levels of each receptor subtype on individual cell types within the hypoxic microenvironment. Given the key role of endothelial cells (ECs) in the development of inflammatory diseases, such as sepsis, rheumatoid arthritis (RA) and atherosclerosis, ARs represent attractive targets for therapeutic intervention in these conditions. In this review, we examine several critical aspects of endothelial function in vivo, assess the role of individual AR subtypes in these events and, where known, discuss the molecular mechanisms by which specific ARs exert their effects.

Hypoxia inducible factor (HIF) in rheumatology: low O2! See what HIF can do!

Maintenance of oxygen homoeostasis is the basic principle in cell proliferation, differentiation, survival, and function in all higher organisms. The transcription factor, HIF (hypoxia inducible factor) has a central role in oxygen homoeostasis, and is indispensably linked to energy metabolism. Abnormally reduced oxygen concentrations leading to dysfunctional cell metabolism are found in rheumatoid arthritis and hence, knowledge of the molecular adaptive responses to hypoxia and the involvement of HIF in the pathogenesis of RA are interesting.

The relationship of VEGF and PGE2 expression to extracellular matrix remodelling of the tenosynovium in the carpal tunnel syndrome

Tenosynovial thickening within the confined space of the carpal tunnel is thought to be the cause of the carpal tunnel syndrome (CTS). However, little is known about the pathological mechanism of tenosynovial thickening. In this study, the role of prostaglandin E(2) (PGE(2)) and vascular endothelial growth factor (VEGF) (two representative molecules that can induce oedema by increasing vascular permeability) was analysed in CTS by using immunohistochemistry and enzyme-linked immunosorptive assay (ELISA). Expression of these molecules was compared with the patients' clinical histories and a temporary increase in production of these molecules was found in cells within the vessels and synovial lining during the intermediate phase of the syndrome when the histology of the tenosynovium changes from oedematous to fibrotic. Statistical analysis clearly demonstrated that there is a close correlation between the expression of PGE(2) and VEGF. Furthermore, immunohistochemical analysis with anti-proliferating cell nuclear antigen (PCNA) revealed that the area with distinct VEGF expression closely matched the area where endothelial cells, vascular smooth muscle cells, and synovial lining cells proliferate. In contrast, despite marked alteration in the extracellular matrix (ECM) component of the tenosynovium, the fibroblasts responsible for most ECM framework production do not proliferate during any phase of CTS. Histological analysis demonstrated that angiogenesis takes place only during the intermediate phase. Since clusters of capillaries and arterioles are often surrounded by type III collagen-rich, disorganized, degenerate connective tissue, which contains fewer fibroblasts than normal, angiogenesis appears to take place as a part of a regenerative reaction that results in fibrosis. These findings strongly indicate that both PGE(2) and VEGF are expressed in the tenosynovium in CTS during the intermediate phase and induce the histological changes seen in the tenosynovium.