Decreased response to IL-12 and IL-18 of peripheral blood cells in rheumatoid arthritis

Reactivation of latent tuberculosis with TNF inhibitors: critical role of the beta 2 chain of the IL-12 receptor

Tumor necrosis factor (TNF) inhibitors have improved a lot the treatment of numerous diseases, with the well-known example of rheumatoid arthritis (RA). In the early 2000s, postmarketing data quickly revealed an alarming number of severe tuberculosis (TB) under such treatment. These findings were consistent with previous results in mice where TNF is essential for lymph node formation and granuloma organization. The effects of TNF inhibition on RA synovium structure are very similar to those on granuloma, with changes in cellular interactions, cytokine, and chemokine production. In addition to the role of TNF in granuloma, the interleukin (IL)-12/interferon (IFN)-γ pathway is required for an efficient host defense against TB. Primary and secondary immunodeficiencies affecting this pathway lead to severe bacillus Calmette-Guérin (BCG) reaction or full TB. Any chronic inflammation as in RA induces a systemic Th1 defect that predisposes to TB through specific downregulation of the IL-12Rß2 chain. When TNF inhibitors are initiated, this transiently increases this risk of TB, through effects on cellular interactions in a latent TB granuloma. At a later stage, when a better control disease activity is obtained, the risk of TB is reduced but not abrogated. Given the clear benefit from TNF inhibition, latent TB infection screening at baseline is essential for an optimal safety.

Medical applications of Cu, Zn, and S isotope effects

This review examines recent applications of stable copper, zinc and sulfur isotopes to medical cases and notably cancer. The distribution of the natural stable isotopes of a particular element among coexisting molecular species varies as a function of the bond strength, the ionic charge, and the coordination, and it also changes with kinetics. Ab initio calculations show that compounds in which a metal binds to oxygen- (sulfate, phosphate, lactate) and nitrogen-bearing moieties (histidine) favor heavy isotopes, whereas bonds with sulfur (cysteine, methionine) favor light isotopes. Oxidized cations (e.g., Cu(ii)) and low coordination numbers are expected to favor heavy isotopes relative to their reduced counterparts (Cu(i)) and high coordination numbers. Here we discuss the first observations of Cu, Zn, and S isotopic variations, three elements closely related along multiple biological pathways, with emphasis on serum samples of healthy volunteers and of cancer patients. It was found that heavy isotopes of Zn and to an even greater extent Cu are enriched in erythrocytes relative to serum, while the difference is small for sulfur. Isotopic variations related to age and sex are relatively small. The ⁶⁵Cu/⁶³Cu ratio in the serum of patients with colon, breast, and liver cancer is conspicuously low relative to healthy subjects. The characteristic time over which Cu isotopes may change with disease progression (a few weeks) is consistent with both the turnover time of the element and albumin half-life. A parallel effect on sulfur isotopes is detected in a few un-medicated patients. Copper in liver tumor tissue is isotopically heavy. In contrast, Zn in breast cancer tumors is isotopically lighter than in healthy breast tissue. ⁶⁶Zn/⁶⁴Zn is very similar in the serum of cancer patients and in controls. Possible reasons for Cu isotope variations may be related to the cytosolic storage of Cu lactate (Warburg effect), release of intracellular copper from cysteine clusters (metallothionein), or the hepatocellular and biosynthetic dysfunction of the liver. We suggest that Cu isotope metallomics will help evaluate the homeostasis of this element during patient treatment, notably by chelates and blockers of Cu trafficking, and understand the many biochemical pathways in which this element is essential.

Update on interleukin-17: a role in the pathogenesis of inflammatory arthritis and implication for clinical practice

Interleukin-17 (IL-17A) is a cytokine critical for the acute defence against extracellular bacterial and fungal infections. Excess production during chronic inflammation has been associated with many inflammatory and autoimmune disorders. The present review describes the key molecules of the IL-17 pathway, which are or could be targeted for treatment. Since targeting of IL-17A may affect defence mechanisms, the pathogenesis of such possible adverse events is analysed. Then the contributions of IL-17 to bone changes in various forms of arthritis are discussed. Finally, the results of current inhibitors of the IL-17 pathway in clinical trials are detailed. IL-17A inhibition has been first registered for the treatment of psoriasis, psoriatic arthritis and ankylosing spondylitis. Other therapeutic options are now tested in a long list of diseases.

Assessing immune function by profiling cytokine release from stimulated blood leukocytes and the risk of infection in rheumatoid arthritis

Persons with rheumatoid arthritis (RA) suffer a high burden of infections, but currently no biomarkers are available to identify individuals at greatest risk. A prospective longitudinal study was therefore conducted to determine the association between the responsiveness of ex vivo cytokine production and 6-month risk of infections. Infections were identified by billing codes and validated by medical record review. At baseline, the release of 17 cytokines by peripheral blood mononuclear cells in response to stimulation, or media alone, was measured using multiplexed cytokine analysis. Production of IL-2, IL-8, IL-10, IL-17, TNF-α, IFN-γ, and GM-CSF, induced by various conditions, was significantly associated with the occurrence of infections. A multivariable prediction model based on these data provided new information on the risk of infection beyond standard assessments of disease activity, severity, and treatment. Future studies could utilize this information to devise new biomarkers for the prediction of infection in patients with RA.

Analysis of complex biomarkers for human immune-mediated disorders based on cytokine responsiveness of peripheral blood cells

The advent of improved biomarkers promises to enhance the clinical care for patients with rheumatoid arthritis (RA) and other immune-mediated disorders. We have developed an innovative approach to broadly assess the cytokine responsiveness of human PBMCs using a multistimulant panel and multiplexed immunoassays. The objective of this study was to demonstrate this concept by determining whether cytokine profiles could discriminate RA patients according to disease stage (early versus late) or severity. A 10-cytokine profile, consisting of IL-12, CCL4, TNF-alpha, IL-4, and IL-10 release in response to stimulation with anti-CD3/anti-CD28, CXCL8 and IL-6 in response to CMV and EBV lysate, and IL-17A, GM-CSF, and CCL2 in response to human heat shock protein 60, easily discriminated the early RA group from controls. These data were used to create an immune response score, which performed well in distinguishing the early RA patients from controls and also correlated with several markers of disease severity among the patients with late RA. In contrast, the same 10-cytokine profile assessed in serum was far less effective in discriminating the groups. Thus, our approach lays the foundation for the development of immunologic "signatures" that could be useful in predicting disease course and monitoring the outcomes of therapy among patients with immune-mediated diseases.

Expression of interleukin-18, IL-18BP, and IL-18R in serum, synovial fluid, and synovial tissue in patients with rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic immunological disease, the invasive monocytes/macrophages and lymphocytes present in synovial cells and synovial tissue produce many cytokines and inflammatory mediators by paracrine signaling and plays a role in the pathological progress in RA patients. Interleukin-18 (IL-18) is a representative proinflammatory factor and displays multiple biological functions. This study was designed to investigate the expression of IL-18 and its receptor (IL-18R) and IL-18 binding protein (IL-18BP) in serum, synovial fluid, and synovial tissue of patients with RA, and to identify the pathological role of IL-18 in RA. Serum, synovial fluid, and synovial tissue were obtained from RA patients. Samples from patients with osteoarthritis and healthy people were obtained as controls. Levels of IL-18, IL-18BP, and PGE2 in serum and synovial fluid were measured by enzyme-linked immunosorbent assay. The biological activity of IL-18 in serum and synovial fluid was detected on the basis of IFN-gamma secretion from IL-18-responding human myelomonocytic KG-1 cells. NO in serum and synovial fluid was detected by Griess reaction. Expression of IL-18, IL-18BP, IL-18R, iNOS, and COX-2 mRNA and protein in synovial tissues was determined by quantitative reverse transcriptase polymerase chain reaction and Western blot. This study shows the expression levels of IL-18, IL-18R, iNOS, COX-2, and the biological activity of IL-18 in both serum and synovial fluid and tissue of patients with RA were significantly increased compared with the corresponding samples from the two control groups. In addition, expression of IL-18BP in patients with RA was decreased compared with samples from the two control groups. In conclusion, the overexpression of IL-18 and IL-18R may play an important role in the pathogenesis of RA.

Cellular targets of interleukin-18 in rheumatoid arthritis

Recent data are presented which indicate a critical role for interleukin (IL)-18 in rheumatoid arthritis (RA). The T cells and macrophages invading the synovium or in the synovial fluid are the chief cellular targets of IL-18 in RA. Neutrophils, dendritic cells and endothelial cells may also be cellular mediators of IL-18. The direct effect of IL-18 on fibroblast-like synoviocytes or chondrocytes may not be essential or important. In RA, IL-18, which is mainly produced by macrophages, activates T cells and macrophages to produce proinflammatory cytokines, chemokines, adhesion molecules and RANKL which, in turn, perpetuate chronic inflammation and induce bone and cartilage destruction.

Clinical significance of IL-18, IL-15, IL-12 and TNF-alpha measurement in rheumatoid arthritis

The aim of the study was to evaluate the clinical significance of serum (S) and synovial fluid (SF) interleukin (IL)-18, IL-15, IL-12 and the tumor necrosis factor alpha (TNF-alpha) measurements in relation to laboratory and clinical measures of disease activity of patients with active rheumatoid arthritis (RA). Sixty-four patients with RA and 25 patients with osteoarthritis (OA) were included in this study. RA activity was determined using the Disease Activity Score (DAS) 28 index. Concentrations of IL-18, IL-15, IL-12 and TNF-alpha were measured by ELISA. Serum C-reactive protein (CRP) levels were also determined. Cross-sectional correlations between S and SF levels of cytokines and values of DAS 28 index were calculated. The results have shown that IL-18, IL-15, IL-12 and TNF-alpha levels in S and SF of patients with RA were significantly higher than the levels obtain from patients with OA (p<0.01). Significantly higher levels of IL-18, IL-15 and TNF-alpha were found in the SF compared to the S of patients with RA (p<0.01). Significantly higher S and SF levels of all four cytokines and serum CRP values were found in RA patients with high disease activity (DAS 28>5.1) compared to those with mild (DAS 28>3.2) and low disease activity (DAS 28>2.6) (p<0.01). Serum and SF concentrations of all four cytokines positively correlated with DAS 28 index values, i.e., disease activity. A poor correlation was found for S and SF IL-12 whereas the highest coefficient of correlation was found for SF IL-18 (r=0.879, p<0.01), and SF TNF-alpha (r=0.827, p<0.01) and disease activity in this study. Strong correlation was found between SF TNF-alpha and SF IL-18 levels (r=0.732, p<0.01). In conclusion, SF IL-18 and TNF-alpha levels in RA patients are good indicators of disease activity. The results obtained support the use of the DAS in clinical practice as a reliable method in assessing disease activity in RA patients.

mRNA Quantification of T-bet, GATA-3, IFN-γ, and IL-4 Shows a Defective Th1 Immune Response in the Peripheral Blood from Rheumatoid Arthritis Patients: Link with Disease Activity

A T helper (Th)1 cytokine profile is predominant in the inflamed synovium of rheumatoid arthritis (RA). Since the situation in the blood is more controversial, we studied the Th1/Th2 balance in the peripheral blood of RA patients using mRNA markers. Total RNA was isolated directly from whole blood from 20 RA patients and 14 healthy controls. T-bet and GATA-3 transcription factors associated with Th1 and Th2 responses respectively, and IFNgamma and IL-4 mRNA levels were measured by real-time PCR. In RA but not in control samples, T-bet mRNA levels correlated positively with IFNgamma mRNA levels, and negatively with CRP levels. Accordingly, RA patients were divided into two groups according to CRP levels. In comparison to RA patients with a low CRP (CRP < 40 mg/l), patients with a high CRP (CRP>or=40 mg/l) had lower IFNgamma/beta-actin, T-bet/beta-actin mRNA levels and T-bet/GATA-3 expression ratios. In conclusion, RA blood cells showed a decreased Th1 situation as indicated by low IFNgamma and T-bet mRNA expression. This pattern was found only in patients with the most active disease.

Expression of toll-like receptors 2 and 4 in rheumatoid synovial tissue and regulation by proinflammatory cytokines interleukin-12 and interleukin-18 via interferon-gamma

OBJECTIVE

To study the expression of Toll-like receptor 2 (TLR-2) and TLR-4 and its association with proinflammatory cytokines in synovial tissue from patients with rheumatoid arthritis (RA), osteoarthritis (OA), and healthy individuals.

METHODS

Synovial tissue specimens from 29 RA patients were stained for TLR-2, TLR-4, and proinflammatory cytokines (interleukin-1beta [IL-1beta], IL-12, IL-17, IL-18, and tumor necrosis factor alpha [TNFalpha]). The expression of TLR-2, TLR-4, and cytokines as well as the degree of inflammation in synovial tissue were compared between patients with RA, patients with OA (n = 5), and healthy individuals (n = 3). Peripheral blood mononuclear cells (PBMCs) were incubated with IL-12 and IL-18, and TLR expression was assessed using fluorescence-activated cell sorter analysis. Production of TNFalpha and IL-6 was measured using Luminex bead array technology.

RESULTS

In RA synovial tissue, the expression of TLR-2 was slightly higher than that of TLR-4. Interestingly, both TLR-2 and TLR-4 were expressed at higher levels in moderately inflamed synovium, as compared with synovial tissue with no or severe inflammation. TLR expression in both the lining and the sublining was associated with the presence of IL-12 and IL-18, but no other cytokines, in the lining. The expression of both TLRs was low in synovial tissue from OA patients and healthy donors. Stimulation of PBMCs with IL-12 and IL-18 resulted in increased expression of both TLR-2 and TLR-4; this could be blocked with anti-interferon-gamma (anti-IFNgamma) antibodies, suggesting a role for IFNgamma. Lipopolysaccharide- or lipoteichoic acid-mediated triggering of PBMCs incubated with IL-12/IL-18 or IFNgamma led to an increased production of both TNFalpha and IL-6, indicating the functionality of TLR-2 and TLR-4.

CONCLUSION

TLR-2 and TLR-4 are expressed in synovial tissue of patients with clinically active disease and are associated with the levels of both IL-12 and IL-18. The synergistic effect of IL-12 and IL-18 on T cell IFNgamma production seems to regulate expression of TLR-2 and TLR-4 in the synovial tissue of RA patients.

Regulation of interleukin-18 binding protein production by blood and synovial cells from patients with rheumatoid arthritis

OBJECTIVE

To study the regulation of interleukin-18 binding protein (IL-18BP) production by rheumatoid arthritis (RA) or control peripheral blood mononuclear cells (PBMCs) and by RA synovial tissue cells, and to compare the levels of IL-18BP messenger RNA (mRNA) expression in whole blood from RA patients and controls.

METHODS

Unstimulated or phytohemagglutinin and phorbol myristate acetate (PHA/PMA)-stimulated PBMCs from 10 RA patients and 12 healthy controls and unstimulated or PHA/PMA-stimulated synovial tissue cells from 8 RA patients were cultured with or without IL-12 (1 ng/ml) and IL-18 (5 ng/ml) alone or in combination. IL-18BP and interferon-gamma (IFN gamma) levels in supernatants were measured by enzyme-linked immunosorbent assay. Levels of IL-18BP and IFN gamma mRNA expression in whole blood samples from 22 RA patients and 12 healthy controls were determined by quantitative reverse transcriptase-polymerase chain reaction.

RESULTS

IL-12 decreased the basal levels of IL-18BP production by freshly isolated RA or control PBMCs, but increased those of synovial cells or PHA/PMA-stimulated PBMCs. IL-18 alone had no direct effect on IL-18BP production by PBMCs or RA synovial cells, with or without stimulation. Unstimulated whole blood samples from RA patients showed lower levels of IL-18BP mRNA expression than those from healthy controls.

CONCLUSION

The production of IL-18BP in response to IL-12 and IL-18 was regulated differently in blood and synovial cells. The difference appears to be related to the level of cell activation.