Anti-tumor necrosis factor therapy increases synovial osteoprotegerin expression in rheumatoid arthritis

OBJECTIVE: Treatment of rheumatoid arthritis (RA) with tumor necrosis factor (TNF)-blocking agents, including etanercept and infliximab, has resulted in reductions in the radiographic progression of RA. However, the exact mechanism by which this protection occurs has not been determined. In order to add to such knowledge, we investigated the effect of anti-TNF therapy on the expression of osteoprotegerin (OPG) and receptor activator of NF-kappaB ligand (RANKL) in synovial tissue. METHODS: The expression of OPG and RANKL in synovial biopsy specimens was evaluated by immunohistochemistry. Serial synovial biopsy specimens were obtained from 18 patients with RA, before and after treatment with etanercept (9 patients) or infliximab (9 patients). Biopsy specimens were evaluated by double-blind semiquantitative analysis and image analysis. The in vitro effect of TNF antagonists on the RANKL/OPG expression in osteoblasts and endothelial cells was evaluated by Western blotting. Statistical analysis was performed using Wilcoxon's signed rank test, followed by the Bonferroni correction for multiple comparisons of paired samples. The results of in vitro experiments were evaluated by one-way analysis of variance, with Tukey's post hoc test. RESULTS: Treatment with both infliximab and etanercept increased the expression of OPG in synovial tissue. After 8 weeks of treatment, neither infliximab nor etanercept influenced RANKL expression. In both groups of patients, the RANKL:OPG ratio decreased following therapy. In vitro, both of the TNF antagonists mimicked the in vivo effect, inducing a decrease in the RANKL:OPG ratio in TNF-primed osteoblasts and endothelial cells. CONCLUSION: Therapy with TNF antagonists in RA modulates the OPG/RANKL system, a potential mechanism that could explain the retardation of radiographic damage observed following anti-TNF therapy.     

Anti–tumor necrosis factor therapy increases synovial osteoprotegerin expression in rheumatoid arthritis

Objective

Treatment of rheumatoid arthritis (RA) with tumor necrosis factor (TNF)–blocking agents, including etanercept and infliximab, has resulted in reductions in the radiographic progression of RA. However, the exact mechanism by which this protection occurs has not been determined. In order to add to such knowledge, we investigated the effect of anti‐TNF therapy on the expression of osteoprotegerin (OPG) and receptor activator of NF‐κB ligand (RANKL) in synovial tissue.

Methods

The expression of OPG and RANKL in synovial biopsy specimens was evaluated by immunohistochemistry. Serial synovial biopsy specimens were obtained from 18 patients with RA, before and after treatment with etanercept (9 patients) or infliximab (9 patients). Biopsy specimens were evaluated by double‐blind semiquantitative analysis and image analysis. The in vitro effect of TNF antagonists on the RANKL/OPG expression in osteoblasts and endothelial cells was evaluated by Western blotting. Statistical analysis was performed using Wilcoxon's signed rank test, followed by the Bonferroni correction for multiple comparisons of paired samples. The results of in vitro experiments were evaluated by one‐way analysis of variance, with Tukey's post hoc test.

Results

Treatment with both infliximab and etanercept increased the expression of OPG in synovial tissue. After 8 weeks of treatment, neither infliximab nor etanercept influenced RANKL expression. In both groups of patients, the RANKL:OPG ratio decreased following therapy. In vitro, both of the TNF antagonists mimicked the in vivo effect, inducing a decrease in the RANKL:OPG ratio in TNF‐primed osteoblasts and endothelial cells.

Conclusion

Therapy with TNF antagonists in RA modulates the OPG/RANKL system, a potential mechanism that could explain the retardation of radiographic damage observed following anti‐TNF therapy.

     

Tumor necrosis factor-alpha induces vascular endothelial growth factor-C expression in rheumatoid synoviocytes

OBJECTIVE: To determine the expression of vascular endothelial growth factor-C (VEGF-C) in the synovial fluid of patients with rheumatoid arthritis (RA) and to investigate the regulation of VEGF-C production by major proinflammatory cytokines in fibroblast-like synoviocytes (FLS). METHODS: The concentrations of VEGF-C, tumor necrosis factor-alpha (TNF-alpha), and interleukin 1beta (IL-1beta) were measured using an ELISA method in synovial fluids obtained from 20 patients with RA and 20 with osteoarthritis (OA). Primary cultured RA FLS were stimulated with TNF-alpha or IL-1beta, and the expression levels of VEGF-C mRNA and protein were assessed by quantitative real-time polymerase chain reaction and ELISA. RESULTS: Significantly higher levels of VEGF-C were found in RA synovial fluids compared to OA synovial fluids. VEGF-C levels showed a highly significant correlation with the levels of both TNF-alpha and IL-1beta in the synovial fluid of patients with RA. TNF-alpha stimulation significantly increased VEGF-C mRNA and protein expression in RA FLS in a dose-dependent manner. A tendency to increased expression of VEGF-C was also observed after IL-1beta stimulation in FLS. CONCLUSION: Overexpression of VEGF-C in FLS by stimulation with TNF-alpha may play an important role in the progression of synovial inflammation and hyperplasia in RA by contributing to local lymphangiogenesis and angiogenesis.     

Tumor necrosis factor-alpha blockade in the treatment of rheumatoid arthritis

The use of TNF alpha antagonists in RA has been extremely instructive. They have taught us that selective targeting of a pathogenic element can provide substantial clinical benefit. They have reinforced the concept of TNF alpha as a pivotal cytokine in the pathogenesis of RA. Pharmacodynamic studies of TNF alpha antagonists have further clarified the pathogenic processes involved in the disease. TNF alpha antagonists have set a new therapeutic standard for RA. Indeed, they are one of the most important advances in the history of the treatment of the disorder. If clinical efficacy is sustained and the safety profile remains benign over the long term, TNF alpha antagonists may replace MTX as the gold standard and become the agent of choice for combination therapy in RA. Further studies are needed to clarify their ultimate position in the therapeutic algorithm.     

Tumor necrosis factor-alpha gene polymorphism in severe and mild-moderate rheumatoid arthritis

OBJECTIVE: To examine whether severe rheumatoid arthritis (RA) carries a -238 or +489 tumor necrosis factor-alpha (TNF-alpha) genotype different from mild-moderate RA. METHODS: We investigated 163 patients (66 with severe disease) and 67 healthy blood donor controls. Genotyping was performed by polymerase chain reaction-restriction fragment length polymorphism. RESULTS: Patients with severe RA (all active disease despite disease modifying antirheumatic drug combination therapy) disclosed the -238 GG genotype in 100% of cases versus 92.8% of the mild-moderates and 92.5% of controls (OR 11.7, Cl 0.6-216, p = 0.03). The +489 AA genotype was seen less often in patients than in controls (OR 4.2. CI 0.97-18.4, p = 0.045), and the contribution to this trend appeared predominant in the anti-TNF treated subgroup. CONCLUSION: The -238 AG genotype was absent in severe RA; in contrast, patients with mild-moderate RA disclosed the same frequency as controls. Thus -238 GG homozygosity is associated with severe RA. The +489 AA genotype might instead protect against worse outcome in RA.     

NF-kappaB-regulated expression of cellular FLIP protects rheumatoid arthritis synovial fibroblasts from tumor necrosis factor alpha-mediated apoptosis

OBJECTIVE: Little apoptosis has been observed in rheumatoid arthritis (RA) synovial tissues. Tumor necrosis factor alpha (TNFalpha) is expressed in the joints of patients with RA, yet RA synovial fibroblasts are relatively resistant to apoptosis induced by TNFalpha. Recently, we demonstrated that FLIP is highly expressed in the RA joint. These studies were performed to determine if TNFalpha-induced NF-kappaB controls the expression of FLIP long (FLIP(L)) and FLIP short (FLIP(S)) in RA synovial fibroblasts and to determine the role of FLIP in the control of TNFalpha-induced apoptosis. METHODS: RA synovial fibroblasts were isolated from RA synovial tissues and used between passages 3 and 9. RA synovial or control fibroblasts were sham infected or infected with a control adenovirus vector or one expressing the super-repressor IkappaBalpha (srIkappaBalpha). The cells were stimulated with TNFalpha or a control vehicle, and expression of FLIP(L) and FLIP(S) was determined by isoform-specific real-time polymerase chain reaction and Western blot analysis. Cell viability was determined by XTT cleavage, and apoptosis was determined by annexin V staining, DNA fragmentation, and activation of caspases 8 and 3. RESULTS: TNFalpha induced the expression of both isoforms of FLIP messenger RNA (mRNA) in RA synovial fibroblasts; however, FLIP(L) was the dominant isoform detected by Western blot analysis. In control fibroblasts, TNFalpha induced the expression of FLIP(L) and FLIP(S) mRNA and protein. The TNFalpha-induced, but not the basal, expression of FLIP was regulated by NF-kappaB. When NF-kappaB activation was suppressed by the expression of srIkappaBalpha, TNFalpha-mediated apoptosis was induced. TNFalpha-induced apoptotic cell death was mediated by caspase 8 activation and was prevented by the ectopic expression of FLIP(L) or the caspase 8 inhibitor CrmA. CONCLUSION: The TNFalpha-induced, but not the basal, expression of FLIP is regulated by NF-kappaB in RA synovial fibroblasts. The resistance of RA synovial fibroblasts to TNFalpha-induced apoptosis is mediated by the NF-kappaB-regulated expression of FLIP. These observations support the role of NF-kappaB and FLIP as attractive therapeutic targets in RA.     

Tumor necrosis factor-alpha (TNF-alpha) converting enzyme contributes to production of TNF-alpha in synovial tissues from patients with rheumatoid arthritis

OBJECTIVE: Expression and function of tumor necrosis factor-alpha (TNF-alpha) converting enzyme (TACE) in synovia of patients with rheumatoid arthritis (RA) were examined to investigate posttranslational regulation of TNF-alpha production by TACE in RA. METHODS: Expression of TACE protein was evaluated by immunohistochemistry. Cytokines and soluble cytokine receptors were measured by ELISA. TACE mRNA was detected by RT-PCR. The enzymatic activity of TACE was measured using TACE-specific fluorogenic substrate. RESULTS: Expression of TACE at protein level in synovial tissue (ST) of patients with RA was significantly stronger than that of patients with osteoarthritis (OA). In RA, TACE was mainly expressed in CD68+ macrophage-like synovial cells. ST from 9 of 9 RA and 3 of 8 OA patients expressed TACE mRNA. RA ST cells possessed significantly higher TACE-like enzymatic activity than OA ST. A synthetic TACE inhibitor significantly reduced the release of TNF-alpha and p75 TNF receptor from RA ST cells. CONCLUSION: TACE is an important regulator of the secretion of TNF-alpha from synovia of patients with RA.     

Tumor necrosis factor-alpha upregulates the expression of immunoglobulin secretory component.

BACKGROUND: The immunoglobulin (Ig) secretory component (SC) is the extracellular component of the polymeric Ig receptor (plgR) that is responsible for the transcytosis of newly synthesized IgA. In addition, the SC seems to play important roles in regulating eosinophil functions and in enhancing local immune responses. SC expression in HT-29 has been shown to increase in response to interferon-gamma, interleukin (IL) 4 and IL-1, but whether tumor necrosis factor (TNF) alpha affects SC expression is disputed. OBJECTIVE: Our aim was to study whether TNF-alpha can affect the expression of SC in Caco-2 cells. METHODS: We used immunocytochemistry, enzyme-linked immunosorbent assay, Western blot, and quantitative real-time polymerase chain reaction to test SC-positive cells, free SC in culture supernatants, plgR mRNA, and protein expression of SC. RESULTS: TNF-alpha dose-dependently increased SC-positive cells, free SC in culture supernatants, plgR mRNA, and protein expression of SC.     

Tumor necrosis factor-alpha promotes proliferation of endometriotic stromal cells by inducing interleukin-8 gene and protein expression

Endometriosis, a common disease among women of reproductive age, is characterized by the presence of endometrial-like tissue outside the uterus. We and others showed that several cytokine levels, including interleukin-8 (IL-8) and tumor necrosis factor-alpha (TNFalpha), are elevated in the peritoneal fluid of women with endometriosis compared with those in women without endometriosis. We also demonstrated that the addition of IL-8 to the culture medium stimulated the proliferation of cultured endometriotic stromal cells. TNFalpha is a multipotent cytokine that induces IL-8 production in various cell types. Therefore, we hypothesized that TNFalpha may also contribute to the pathogenesis of endometriosis by inducing the production of IL-8. To test this hypothesis, we analyzed the peritoneal fluid concentrations of IL-8 and TNFalpha using enzyme-linked immunosorbent assay (ELISA). We observed a significant correlation between the levels of TNFalpha and IL-8 in the peritoneal fluid of endometriosis patients. We also obtained the endometriotic stromal cells from chocolate cyst linings of the ovary. The expression of the receptors for TNFalpha (TNFR) was examined by RT-PCR. We observed the expression of both TNFR-I and TNFR-II genes in endometriotic stromal cells. The expression of IL-8 gene and protein was analyzed by Northern blot hybridization and enzyme-linked immunosorbent assay, respectively. TNFalpha induced the gene and protein expression of IL-8 in endometriotic stromal cells in a dose-dependent fashion. The addition of TNFalpha promoted the proliferation of the endometriotic stromal cells, and the stimulatory effects of TNFalpha were abolished by adding anti-IL-8 antibody. We demonstrated for the first time that TNFalpha stimulated proliferation of endometriotic stromal cells through induction of IL-8 gene and protein expression. We concluded that the TNFalpha may be one of the essential factors for the pathogenesis of endometriosis.     

Tumor necrosis factor-alpha promotes atherosclerotic lesion progression in APOE*3-Leiden transgenic mice

OBJECTIVE: Tumor necrosis factor-alpha (TNFalpha) is a pleiotropic cytokine exerting both inflammatory and cell death modulatory activity, and is thought to play a role in the pathogenesis of atherosclerosis. Studies in mice indicated that TNFalpha affects atherosclerosis minimally or not under conditions that allow fatty streak formation. Here, we examined the possible role of TNFalpha in advanced and complex atherosclerotic lesions. METHODS AND RESULTS: To induce atherosclerosis, TNFalpha-deficient (Tnf-/-) APOE*3-Leiden and control APOE*3-Leiden only mice were fed a cholesterol-rich diet. Comparable levels of plasma cholesterol and triglycerides and the systemic inflammatory parameters, serum amyloid A and soluble intercellular adhesion molecule-1 were found in APOE*3-LeidenTnf-/- and control mice. Although absence of TNFalpha did not affect the quantitative area of atherosclerosis, APOE*3-LeidenTnf-/- mice had a higher relative number of early lesions (46.1% vs. 21.4%) and a lower relative number of advanced lesions (53.9% vs. 78.6%, P=0.04). In addition, the advanced lesions in APOE*3-LeidenTnf-/- mice showed less necrosis (9.9+/-12.1% vs. 23.4+/-19.3% of total lesion area, P=0.04) and an increase in apoptosis (1.5+/-1.5% vs. 0.4+/-0.6% of total nuclei, P=0.03). CONCLUSIONS: Our data indicate that TNFalpha stimulates the formation of lesions towards an advanced phenotype, with more lesion necrosis and a lower incidence of apoptosis.     

Tumor necrosis factor-alpha at acute myocardial infarction in rats and effects on cardiac fibroblasts

Tumor necrosis factor-alpha (TNF-alpha) biosynthesis by the myocardium in response to several diseases has not been solely associated with activation of the immune system but may also serve as a stress response in the context of neurohumoral gene activation. In this regard, beneficial as well as adverse effects of the cytokine on injured myocardium have been reported. TNF-alpha has been suggested to modulate myocyte and fibroblast cell growth and function. Now, in a rat model of acute myocardial infarction TNF-alpha expression and effects on cardiac fibroblast were determined. TNF-alpha was detected in rat hearts with acute myocardial infarction, parallel to the presence of proliferating fibroblasts, at the border zone of the infarct region, to a lesser degree in the infarct zone and was still present in the surviving myocardium. Similarly, the TNF-alpha mRNA level was, compared to sham-operated heart, higher in the infarct area. In the remote myocardium, a trend to an elevated TNF-alpha mRNA level was observed. TNF-alpha stimulated proliferation and expression of fibronectin in fibroblasts isolated from the infarct, non-infarct-region and sham-operated hearts. Angiotensin II is mitogenic for fibroblasts post-myocardial infarction and effects might be mediated indirectly by TNF-alpha. Addition of a neutralising anti-TNF-alpha antibody inhibited angiotensin II stimulated proliferation of fibroblasts only from the infarcted myocardium. The regional differences in TNF-alpha protein and mRNA levels, parallel to proliferating fibroblasts and proliferative effects may foster the reparative, reactive and adverse post-infarct remodeling of the heart.     

Tumor necrosis factor-alpha and Interleukin-10 gene promoter polymorphisms in Turkish rheumatoid arthritis patients

Tumor necrosis factor and interleukin 10 have been implicated in the pathogenesis of rheumatoid arthritis (RA). Certain single-nucleotide polymorphisms (SNPs) within the promoter region of the IL-10 and TNF genes have been associated with altered levels of circulating IL10 and TNF. We aimed to explore the association of IL-10 and TNF-alpha polymorphisms in Turkish RA patients. We analyzed the association of TNF-alpha (-308G/A, -238G/A, -376G/A) and IL10 (-1082G/A, -819C/T, -592C/A) polymorphisms in 98 Turkish patients with rheumatoid arthritis and 122 healthy subjects using ARMS-PCR. The correlation of these findings with RF positivity and erosive disease in RA patients was also sought. A significant association was found between having RA and -1082 G allele (p = 0.008; OR = 1.44, 95% CI 1.11-1.86). There was no association between RA and -819C/T polymorphism. Significant differences were observed in IL10 GCC and ACC haplotypes distribution between RA and control subjects (p = 0.006; OR = 1.46, 95% CI 1.13-1.89 and p = 0.011; OR = 1.43, 95% CI 1.09-1.88, respectively). No statistically significant association was found between TNF-alpha 308G/A, -238G/A, -376G/A polymorphisms and RA. No significant association was found between RF positivity and erosive disease and TNF-alpha, IL10 gene polymorphisms. In addition, when combined genotypes were analyzed, no significant difference was found between RA patients and healthy controls. Our findings suggest that IL-10 1082 G/A polymorphism or GCC, ACC haplotypes may be associated with RA in Turkish patients.