The role of interleukin-1 receptor antagonist in the prevention and treatment of disease

Abstract

?Interleukin-1 (IL-1) and tumor necrosis factor α (TNF-α) play key proinflammatory roles in a variety of human diseases, including rheumatoid arthritis (RA). IL-1 receptor antagonist (IL-1Ra) is a naturally occurring structural variant of IL-1 that competitively inhibits receptor binding of IL-1. Four forms of IL-1Ra have been described: secretory IL-1Ra (sIL-1Ra) and three intracellular molecules (icIL-1Ra1, 2, and 3). Excess amounts of IL-1Ra are necessary to inhibit the biological effects of IL-1. The endogenous production of IL-1Ra plays an anti-inflammatory role, but the level of production of IL-1Ra in inflamed tissues may not be adequate to block IL-1 effectively. An allelic polymorphism in the IL-1Ra gene is associated with a variety of human diseases, largely of epithelial or endothelial cell origin. The disease associated allele IL1RN*2 may lead to a decreased production of icIL-1Ra1 by these cells, predisposing the patient to an imbalance in the IL-1 system. The therapeutic administration of IL-1Ra was found to be safe and efficacious in the treatment of RA. Intraarticular delivery of the IL-1Ra cDNA by ex vivo gene therapy in patients with RA was effective in enhancing local IL-1Ra production. This unique form of therapy is under further evaluation.     

Interleukin-1 receptor antagonist is upregulated during diet-induced obesity and regulates insulin sensitivity in rodents

Aims/hypothesis The IL-1 receptor antagonist (IL-1Ra) is an anti-inflammatory cytokine known to antagonise the actions of IL-1. We have previously shown that IL-1Ra is markedly upregulated in the serum of obese patients, is correlated with BMI and insulin resistance, and is overexpressed in the white adipose tissue (WAT) of obese humans. The aim of this study was to examine the role of IL-1Ra in the regulation of glucose homeostasis in rodents. Methods We assessed the expression of genes related to IL-1 signalling in the WAT of mice fed a high-fat diet, as well as the effect of Il1rn (the gene for IL-1Ra) deletion and treatment with IL-1Ra on glucose homeostasis in rodents. Results We show that the expression of Il1rn and the gene encoding the inhibitory type II IL-1 receptor was upregulated in diet-induced obesity. The blood insulin:glucose ratio was significantly lower in Il1rn ^−/− animals, which is compatible with an increased sensitivity to insulin, reinforced by the fact that the insulin content and pancreatic islet morphology of Il1rn ^−/− animals were normal. In contrast, the administration of IL-1Ra to normal rats for 5 days led to a decrease in the whole-body glucose disposal due to a selective decrease in muscle-specific glucose uptake. Conclusions/interpretation The expression of genes encoding inhibitors of IL-1 signalling is upregulated in the WAT of mice with diet-induced obesity, and IL-1Ra reduces insulin sensitivity in rats through a muscle-specific decrease in glucose uptake. These results suggest that the markedly increased levels of IL-1Ra in human obesity might contribute to the development of insulin resistance.     

Interleukin-17 gene expression in patients with rheumatoid arthritis

Interleukin-17 is a proinflammatory cytokine. Recent animal studies have shown that IL-17 plays a role in the initiation and progression of arthritis. However, whether IL-17 has a prominent role in human rheumatoid arthritis (RA) or not remains unclear. Here we investigated the role of IL-17 in patients with RA. cDNA was prepared from knee joint synovial tissues of RA (n = 11) and osteoarthritic (OA, n = 10) patients and PBMC of RA (n = 52) and healthy subjects (n = 34). IL-17 gene expression level was measured by real-time PCR, and was compared with various clinical parameters. IL-17 gene expression in synovial tissues of RA was similar to that in OA. IL-17 gene expression level in PBMC of RA patients was significantly higher than in the control. The response (changes in DAS) to two-week treatment with anti-TNF-α blockers (infliximab or etanercept) did not correlate with changes in IL-17 gene expression levels. The IL-17/TNF-α gene expression ratio at baseline (before treatment) tended to be lower in responders to the treatment. Expression of IL-17 gene in PBMC may be associated with the inflammatory process of RA. IL-17/TNF-α expression ratio is a potentially suitable marker of response to anti-TNF-α therapy.     

Differential in vitro effects of IL-4, IL-10, and IL-13 on proinflammatory cytokine production and fibroblast proliferation in rheumatoid synovium

The purpose of this study was to compare the potential of interleukin-4 (IL-4), IL-10, and IL-13 to interrupt two major inflammatory pathways in rheumatoid arthritis (RA), i.e., overexpression of proinflammatory cytokines and cytokine-mediated fibroblast growth. IL-4, IL-10, and IL-13 were all able to significantly inhibit the production of IL-1β, tumor necrosis factor-α (TNF-α), IL-6, and IL-8 by freshly isolated RA synovial tissue cells; IL-10 was most effective in terms of IL-1β and TNF-α reduction. The IL-1 receptor antagonist was enhanced by IL-4 and IL-13, but only slightly enhanced by IL-10. Spontaneous interferon-γ secretion was diminished by IL-4 and IL-10 but not by IL-13. Addition of anti-IL-10 neutralizing antibody to RA synovial tissue cells resulted in a substantial increase in IL-1β and TNF-α levels, whereas neither anti-IL-4 nor anti-IL-13 antibody had a significant effect. IL-1β-stimulated proliferation of RA synovial fibroblast cell lines was inhibited by IL-4 and IL-13, but not by IL-10; IL-4 was over tenfold more effective than IL-13. These results suggest that IL-4, IL-10, and IL-13 all have the therapeutic potential to regulate the disease activity mediated by proinflammatory cytokines in RA, but each cytokine may have different potencies. Received: 29 June 2000 / Accepted: 20 July 2000     

IL-38 binds to the IL-36 receptor and has biological effects on immune cells similar to IL-36 receptor antagonist

The functional role of IL-1 family member 10, recently renamed IL-38, remains unknown. In the present study we aimed to elucidate the biological function of IL-38 and to identify its receptor. Heat-killed Candida albicans was used to stimulate memory T-lymphocyte cytokine production in freshly obtained human peripheral blood mononuclear cells from healthy subjects. The addition of recombinant IL-38 (152 amino acids) inhibited the production of T-cell cytokines IL-22 (37% decrease) and IL-17 (39% decrease). The reduction in IL-22 and IL-17 caused by IL-38 was similar to that caused by the naturally occurring IL-36 receptor antagonist (IL-36Ra) in the same peripheral blood mononuclear cells cultures. IL-8 production induced by IL-36γ was reduced by IL-38 (42% decrease) and also was reduced by IL-36Ra (73% decrease). When human blood monocyte-derived dendritic cells were used, IL-38 as well as IL-36Ra increased LPS-induced IL-6 by twofold. We screened immobilized extracellular domains of each member of the IL-1 receptor family, including the IL-36 receptor (also known as "IL-1 receptor-related protein 2") and observed that IL-38 bound only to the IL-36 receptor, as did IL-36Ra. The dose-response suppression of IL-38 as well as that of IL-36Ra of Candida-induced IL-22 and IL-17 was not that of the classic IL-1 receptor antagonist (anakinra), because low concentrations were optimal for inhibiting IL-22 production, whereas higher concentrations modestly increased IL-22. These data provide evidence that IL-38 binds to the IL-36R, as does IL-36Ra, and that IL-38 and IL-36Ra have similar biological effects on immune cells by engaging the IL-36 receptor.     

Etanercept reduces the serum levels of interleukin-23 and macrophage inflammatory protein-3 alpha in patients with rheumatoid arthritis

The purpose of this study was to analyze the effect of the soluble TNF-α receptor etanercept on the serum levels of IL-16, IL-17, IL-23, and macrophage inflammatory protein-3α (MIP-3α) in rheumatoid arthritis (RA) patients. Twenty-two patients with RA were administered etanercept once or twice a week for more than 6 months, and we evaluated clinical and laboratory parameters and serum levels of IL-16, IL-17, IL-23, and MIP-3α at the baseline and at 3 and 6 months. Additionally, the production of IL-23 and MIP-3α of cultured synovial cells stimulated with TNF-α from RA patients was determined by ELISA. We also used ELISA kits to determine synovial fluid (SF) levels of IL-17, IL-23, and MIP-3α in patients with RA, osteoarthritis (OA), pseudogouty arthritis (PGA), and gouty arthritis (GA). A significant decrease in serum levels of IL-23 and MIP-3α was observed at 3 and 6 months after initial treatment of etanercept. TNF-α induced MIP-3α but not IL-23 production in cultured synovial cells from RA patients. SF levels of IL-17, IL-23, and MIP-3α in RA patients showed significantly higher levels than those of OA, PGA, and GA patients. This study demonstrated that the reduction of IL-23 and MIP-3α production in RA patients was a newly determined function of etanercept     

Dysregulation of the in vivo production of interleukin-1 receptor antagonist in patients with rheumatoid arthritis pathogenetic implications

Objective. Patients with rheumatoid arthritis (RA) have defective hypothalamic responses to inflammation, possibly because of excessive production of cytokine inhibitor, which could blunt the effects of cytokines on the hypothalamus, or because of an imbalance between interleukin-1β (IL-1β) and interleukin-1 receptor antagonist (IL-1Ra), which could create a mainly proinflammatory state. The present study was undertaken to investigate these possibilities. Methods. The in vivo kinetics of IL-1β and IL-1Ra secretion were studied in patients with RA, osteoarthritis (OA), and chronic osteomyelitis (OM), and in normal controls before and after surgery. Results. The 24-hour levels of IL-1Ra were significantly increased in RA (P < 0.001), but there was no diurnal variation in any group. Preoperative levels of IL-1Ra were higher in RA and OA sera (P = 0.001). After surgery, IL-1Ra behaved like an acute-phase reactant protein in all subjects. IL-1β was 10–20 times higher in RA than in OM and OA patients at baseline, but the percentage increase in all groups postoperatively was the same. RA patients had an IL-1Ra:IL-1β ratio of 26.2 ± 3.7 (mean ± SEM) at baseline (OM patients 89.2 ± 5.8 and OA patients 1,310 ± 363); this increased to 66.5 ± 19.8 after surgery (OM patients 120 ± 6.7 and OA patients 325.8 ± 106). Conclusion. RA patients have a dysregulation of IL-1Ra production, and it seems unlikely that the defective hypothalamic response seen in RA is due to a functional deficit of IL-1β.     

Activin A suppresses interleukin-1-induced matrix metalloproteinase 3 secretion in human chondrosarcoma cells

The objective was to investigate the effect of activin A on matrix metalloproteinase 3 (MMP-3) production and to identify the role of activin A in chondroprotection. SW1353 cells, a human chondrosarcoma cell line, were stimulated with interleukin (IL) 1α and tumor necrosis factor (TNF) α, and the concentrations of activin A, follistatin, and MMP-3 secreted into the culture media were measured by enzyme-linked immunosorbent assay (ELISA). Activin A was added to cell cultures in the presence of IL-1α or TNFα to determine its effect on the production of MMP-3 and sulfated glycosaminoglycan (sGAG) (measured by Alcian blue assay). To study the mechanism responsible for the chondroprotective effects of activin A, the production of IL-1 receptor antagonist (IL-1ra) and tissue inhibitor for metalloproteinases 1 (TIMP-1) was examined by ELISA. Addition of IL-1α did not affect the production of activin A by cultured SW1353 cells. IL-1α and activin A inhibited the production of follistatin. Stimulation of SW1353 cells with activin A suppressed IL-1α-induced, but not TNFα-induced, MMP-3 expression. Activin A had no effect on the production of sGAG, IL-1ra, or TIMP-1, although it suppressed the induction of TIMP-1 and IL-1ra by IL-1α. This novel finding of MMP-3 inhibition by activin A suggests a new role of activin A in cartilage remodeling. Activin A may have therapeutic potential for preventing cartilage degradation.     

Interleukin-1 receptor antagonist gene polymorphism in chinese patients with systemic lupus erythematosus

The purpose of this study was to determine whether IL-1 receptor antagonist (IL-1Ra) gene polymorphism is a marker of susceptibility to or severity of systemic lupus erythematosus (SLE) in Chinese patients. The study included 52 Chinese patients with SLE. One hundred and three unrelated, healthy individuals living in central Taiwan served as controls. From genomic DNA, the polymorphism of the gene for IL-1Ra was typed. Allelic frequencies and carriage rates were compared between SLE patients and controls. The relationship between allelic frequencies and clinical manifestations of SLE was evaluated. We found an increased frequency of IL1RN*2 in the SLE patients compared to normal controls (χ²= 4.15, P<0.05), with an odds ratio (of allele frequency) of 2.63 (95% confidence interval 1.00–6.96). The carriage rate of IL1RN*2 was also higher in the SLE patients (6.8% in the controls vs. 17.3% in the SLE patients). We observed increased frequencies of malar rash and photosensitivity among patients with IL1RN*2 (77.8%) compared to patients without the allele (48.8%). However, this difference did not reach statistical significance (χ² = 2.51, P= 0.11). This study indicated that the frequency of IL1RN*2 is higher in Chinese SLE patients than in Chinese normal controls in Taiwan. However, there was no association between the frequency of IL1RN*2 and clinical manifestations. Received: 4 May 2001 / Accepted: 17 November 2001     

Impaired counter-regulation of interleukin-1 by the soluble IL-1 receptor type II in patients with chronic liver disease

Objective. To assess the production of the endogenous IL-1 modulators IL-1 receptor antagonist (IL-1Ra), type I and II soluble IL-1 receptors (IL-1sRI and II) in patients with chronic liver disease (CLD). Material and methods. Plasma levels of IL-1beta (IL-1β) and IL-1 modulators were assessed in 126 CLD patients and 39 healthy controls. IL-1sRII was also measured in the supernatants of primary hepatocyte cultures. Results. Plasma IL-1sRI and IL-1Ra levels were significantly higher in cirrhotic CLD patients than in non-cirrhotic CLD patients and in controls. Levels did not depend on the etiology of CLD. Likewise, plasma IL-1β levels were elevated in CLD patients compared with those in controls. In contrast, IL-1sRII levels did not differ between CLD patients and controls. Cultures of human primary hepatocytes showed that IL-1sRII is induced by IL-1β, but not IL-6. Conclusions. In cirrhotic CLD patients elevated plasma IL-1β is not counteracted by endogenous levels of IL-1sRII, whereas high IL-1sRI is expected to neutralize the naturally occurring antagonist IL-1Ra, resulting in a dysregulation of the IL-1 system that might enhance pro-inflammatory activity of IL-1.     

Gene transfer to human joints: progress toward a gene therapy of arthritis

This article describes the clinical application of gene therapy to a nonlethal disease, rheumatoid arthritis (RA). Intraarticular transfer of IL-1 receptor antagonist (IL-1Ra) cDNA reduces disease in animal models of RA. Whether this procedure is safe and feasible in humans was addressed in a phase I clinical study involving nine postmenopausal women with advanced RA who required unilateral sialastic implant arthroplasty of the 2nd-5th metacarpophalangeal (MCP) joints. Cultures of autologous synovial fibroblasts were established and divided into two. One was transduced with a retrovirus carrying IL-1Ra cDNA; the other provided untransduced, control cells. In a dose escalation, double-blinded fashion, two MCP joints were injected with transduced cells, and two MCP joints received control cells. One week later, injected joints were resected and examined for evidence of successful gene transfer and expression by using RT-PCR, ex vivo production of IL-1Ra, in situ hybridization, and immunohistochemistry. All subjects tolerated the protocol well, without adverse events. Unlike control joints, those receiving transduced cells gave positive RT-PCR signals. Synovia that were recovered from the MCP joints of intermediate and high dose subjects produced elevated amounts of IL-1Ra (P = 0.01). Clusters of cells expressing high levels of IL-1Ra were present on synovia of transduced joints. No adverse events occurred. Thus, it is possible to transfer a potentially therapeutic gene safely to human rheumatoid joints and to obtain intraarticular, transgene expression. This conclusion justifies additional efficacy studies and encourages further development of genetic approaches to the treatment of arthritis and related disorders.     

Suppressive effect of ethanol on the expression of hepatic asialoglycoprotein receptors augmented by interleukin-1β, interleukin-6, and tumor necrosis factor-α

Blood levels of inflammatory-related cytokines, including interleukin (IL)-1β, IL-6, and tumor necrosis factor (TNF)-α, are elevated in patients with alcoholic liver diseases. We investigated the effects of these cytokines and ethanol on the expression of hepatic asialoglycoprotein receptors (AGPRs) in a human hepatoblastoma cell line, HepG2. An [¹²⁵I]-asialo-orosomucoid binding assay showed significant increases in surface AGPR numbers in HepG2 cells by treatment with IL-1β, IL-6, and TNF-α, to levels which were approximately 130% of the values in untreated control cells. However, the enhanced AGPR numbers induced by treatment with these cytokines were markedly suppressed, to 70%–80% of the number in the untreated cells, by treatment with ethanol. Immunological detection of AGPR with a specific antibody demonstrated that the modulation of surface AGPR numbers was correlated with the cellular expression levels of AGPR. These results suggest that, although IL-1β, IL-6, and TNF-α stimulate the synthesis of hepatic AGPR, ethanol suppresses the expression of AGPR augmented by these cytokines. This leads to an increase in serum asialo-orosomucoid levels caused by the disordered catabolism mediated by AGPR in patients with alcoholic liver disease. (Received Dec. 5, 1997; accepted May 22, 1998)     

Inflammation and mortality in a frail mouse model

Mice homozygous for targeted deletion of the interleukin 10 gene (Il-10) have been partially characterized as a model for human frailty. These mice have increased serum interleukin (IL)-6 in midlife, skeletal muscle weakness, and an altered skeletal muscle gene expression profile compared to age and sex-matched C57BL/6 (B6) control mice. In order to further characterize for use as a frailty model, we evaluated the evolution of inflammatory pathway activation, endocrine change, and mortality in these mice. Serum was collected in groups of age- and sex-matched B6.129P2-Il10 ^tm1Cgn /J (IL-10^tm/tm) mice and B6 control mice at age 12, 24, 48, 72, and 90 weeks. Cytokines including IL-6, interleukin 1 beta (IL-1β), tumor necrosis factor-alpha (TNF-α), interferon-gamma (IFN-γ), chemokine (C-X-C motif) ligand 1 (KC), IL-12, and IL-10 were measured using electro-chemiluminescent multiplex immunoassay and insulin-like growth factor 1 (IGF-1) was measured using solid-phase enzyme-linked immunosorbent assay. A separate longitudinal cohort was monitored from age 35 weeks to approximately 100 weeks. Survival was evaluated by Kaplan–Meier survival estimates and detailed necropsy information was gathered in a subset of mice that died or were sacrificed. In IL-10^tm/tm mice compared to B6 controls, serum IL-6, IL-1β, TNF-α, IFN-γ, KC levels were significantly elevated across the age groups, serum mean IGF-1 levels were higher in the 48-week-old groups, and overall mortality rate was significantly higher. The quadratic relationship between IGF-1 and age was significantly different between the two strains of mice. Serum IL-6 was positively associated with IGF-1 but the effect was significantly larger in IL-10^tm/tm mice. These findings provide additional rationale for the use of the IL-10^tm/tm mouse as a model for frailty and for low-grade inflammatory pathway activation.     

Prostaglandin E2 receptors EP1 and EP4 are up-regulated in rabbit chondrocytes by IL-1β, but not by TNFα

Prostaglandin E2 (PGE2) exerts its actions through the binding of the high affinity EP receptors. We wanted to evaluate the regulation of EP1 and EP4, and the expression of cyclooxigenase (COX)-2, main enzyme responsible for PGE2 synthesis in inflammatory situations, in healthy rabbit chondrocytes stimulated with inflammatory mediators locally increased during osteoarthritis. Articular chondrocytes obtained from healthy rabbits were stimulated with interleukin (IL)-1β (0.1–100 u/ml) or tumour necrosis factor (TNF)α (100 ng/ml). Where indicated, cells were preincubated with non-steroidal antiinflammatory drugs (NSAIDs) (10⁻⁶ M) to inhibit PGE2 synthesis. IL-1β induced a dose and time-dependent increase in EP1, EP4 and COX-2 expression. However, TNFα presence did not induce a significant modification in EP1, EP4 or COX-2 gene expression at any time of study. NSAID presence significantly inhibited PGE2 release but did not modify the EP receptors or COX-2 expression induced by IL-1β. Our results indicate that EP1 and EP4 receptors, and COX-2 are up-regulated in IL-1β-stimulated chondrocytes, while no significant modifications are observed in TNFα-stimulated cells. NSAIDs were unable to modify the expression of these mediators induced by IL-1β. Therefore, the increase in PGE2 synthesis, induced by IL-1β, does not seem to mediate the increase in EP receptor expression, in rabbit chondrocytes.     

The levels of leukemia inhibitory factor in synovial tissues of patients with rheumatoid arthritis: inflammation and other proinflammatory cytokines

 To clarify the effect of leukemia inhibitory factor (LIF) on the destruction of rheumatoid arthritis (RA) joints, we investigated the production of LIF and the expression of LIF mRNA in synovial tissues from patients with RA and osteoarthritis (OA). Synovial fluids from RA were used to measure the LIF concentrations using enzyme-linked immunosorbent assay (ELISA). Immunohistochemistory and RT-PCR were used to examine the expression of LIF by synovial cells. LIF mRNA was detected in all cases in RA synovial cells. Although LIF protein was detected only in 20 cases (19%) in RA synovial fluids, LIF concentration in the synovial fluids significantly correlated with the peripheral leukocyte count (P < 0.001) and C-reactive protein (CRP) (P < 0.01). Moreover, levels of IL-1β, IL-6, and IL-8, but not TNF-α, were significantly correlated with LIF in the RA synovial fluids. LIF production was promoted by IL-1β and TNF-α stimulation; in contrast, IL-1 ra and IL-4 were found to markedly decrease LIF production by cultured synovial cells. LIF appeared to be a cytokine produced by RA synovium leading to a proinflammatory secretion profile. Moreover, IL-4 and IL-1 ra may represent attenuated activity for reducing the effect of the destruction of joints by LIF. Received: February 12, 2002 / Accepted: September 6, 2002     

Blocking the effects of IL-1 in rheumatoid arthritis protects bone and cartilage

Destruction of articular joints occurs progressively in patients with rheumatoid arthritis (RA). Although the exact aetiology of RA has not been fully elucidated, a large body of evidence supports a role for interleukin-1 (IL-1) in cartilage and bone erosion. In vitro studies suggest that IL-1 can cause cartilage destruction by stimulating the release of matrix metalloproteinases and other degradative products, and it can increase bone resorption by stimulating osteoclast differentiation and activation. In animal models of RA, blocking the effects of IL-1 with either IL-1 receptor antagonist (IL-1Ra; endogenous), anti-IL-1 monoclonal antibodies, or soluble IL-1 type II receptors significantly reduced cartilage destruction and bone erosion. Gene therapy with IL-1Ra was also effective in reducing joint destruction in experimental RA and osteoarthritis (OA) models. In clinical studies, anakinra, a human recombinant IL-1 receptor antagonist (IL-1ra; exogenous), significantly slowed radiographic progression of RA relative to placebo and significantly reduced clinical symptoms when used as monotherapy or in addition to existing methotrexate therapy. These results demonstrate that blocking IL-1 protects bone and cartilage from progressive destruction in RA.     

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.