Interleukin-6: discovery of a pleiotropic cytokine

Serum levels of anti-CCP antibodies, anti-MCV antibodies and RF IgA in the follow-up of patients with rheumatoid arthritis treated with rituximab

Rheumatoid arthritis (RA) is characterized by the presence of circulating rheumatoid factor (RF) and anticitrullinated peptide antibodies (ACPA), which are positive in about 70-80% of patients. APCA have a higher specificity and therefore a higher diagnostic power than RF, but are less informative than RF in monitoring the course of the disease in patients under treatment. Recently, it has been reported that the anticitrullinated vimentin (a-MCV) antibody test can identify a particular subgroup of APCA that may be negative for anticyclic citrullinated peptide (a-CCP) antibodies. Concerning RF, the RF IgA isotype has been described as a more specific marker of erosive joint damage than total RF. The aim of our study was to monitor the levels of a-CCP, a-MCV, total RF and RF IgA in the follow-up of patients with RA treated with B-lymphocytedepletive rituximab (RTX), to detect any differences or peculiarities in patterns of these autoantibodies, especially in relation to their potential use as predictive markers of therapeutic response. We studied 30 patients with RA treated with RTX. All patients were previously unresponsive to at least 6 months of therapy with disease-modifying antirheumatic drugs (DMARDs; methotrexate, leflunomide, cyclosporine, chloroquine) and/or at least 6 months of therapy with anti-TNF biologics. The evaluation of response to RTX was made at month +6 using the EULAR criteria (DAS28). a-CCP, a-MCV, total RF and RF IgA were determined at baseline (before the first infusion of RTX) and after 1, 3 and 6 months. In serum samples obtained before treatment two cytokines essential for Blymphocyte proliferation, interleukin 6 (IL-6) and B-lymphocyte stimulator (BLyS) were also determined. In all patients a significant and consistent reduction in all the tested antibodies was found during follow-up, with no differences in respect of the degree of response to RTX. Of note, at baseline, generally a higher titre of all autoantibodies was seen in patients who then showed a better response to RTX. Finally, there were no differences in serum concentrations of IL-6 and BLyS in patients in relation to the presence or absence of the autoantibodies investigated, nor was there any significant correlation between the serum concentrations of the cytokines and the titres of the autoantibodies. Thus, neither a-MCV compared to a- CCP, nor RF IgA compared to routine total RF, provided any additional predictive information in the follow-up of patients with RA treated with RTX.

Antibody immunosuppressive therapy in solid organ transplant: Part II

The use of antibodies in transplantation dates to 1986 when muromonab CD3, a monoclonal antibody (mAb) targeting CD3, was first approved for prevention and treatment of renal allograft rejection. These agents have largely been used in a brief adjunctive manner to provide immunosuppression during the initial period after solid organ transplantation or during an episode of acute rejection. Recent advances in our understanding of transplant immunology have allowed emergence of numerous new mAbs, targeting co-stimulatory signals, cell surface receptors and novel protein constructs. During the next decade, transplant professionals will increasingly require knowledge of the mechanisms and pharmacologic characteristics of these novel therapeutic agents.

The CC homozygosis of the -174G>C IL-6 polymorphism predicts a lower efficacy of rituximab therapy in rheumatoid arthritis

Identification of genetic biomarkers of response to biologics in rheumatoid arthritis (RA) is a relevant issue. Being IL-6 a key cytokine for B cell survival, the interleukin-6 (IL-6) -174G>C and the IL-6 receptor (IL-6R) D358A gene polymorphisms were investigated in 158 RA patients treated with rituximab (RTX). One hundred and twenty-eight (81.0%) were RF positive and 126 (79.7%) were anti-CCP positive. Response to therapy was evaluated at the end of the sixth month after the first RTX infusion, by using both the EULAR and the ACR criteria. The possible relationship with IL-6 serum levels was also studied. By univariate analysis, lack of response by the EULAR criteria was more prevalent in RA patients with the IL-6 -174 CC genotypes (39.1%), than in the GC/GG patients (18.5%) (OR 2.83; 95%CI=1.10-7.27; p=0.031). A good response was noticed in only one patient (4.3%) with the IL-6 -174 CC genotype, while it was present in 24.4% of GG/GC cases (p=0.06). By stepwise multivariate analysis (including RA duration, baseline DAS28, baseline HAQ, RF status, anti-CCP status and IL-6 genotype as covariates), the IL-6 -174CC genotype was selected as an independent predictor of no response to RTX by both EULAR and ACR≥50 criteria, while the IL-6R polymorphism resulted as not associated. No definite association between gene polymorphisms and IL-6 serum levels was noticed. Present results suggest a possible role for IL-6 genotyping to better plan treatment with RTX in RA, and larger studies are worthwhile.

Efficacy and tolerability of tocilizumab in rheumatoid arthritis patients seen in daily clinical practice in Japan: results from a retrospective study (REACTION study)

Tocilizumab, a humanized monoclonal antibody to the interleukin 6 (IL-6) receptor, was approved for use as rheumatoid arthritis (RA) therapy in Japan in 2008, but its efficacy and tolerability in daily practice has not yet been reported. We report the results of a multicenter retrospective study on the efficacy and safety of tocilizumab involving all patients (n = 229) who were started on tocilizumab therapy at three rheumatology institutes in Japan from April 2008 through to March 2009. Tocilizumab was infused every 4 weeks at a dose of 8 mg/kg according to the drug labeling. Among the 229 patients, 55% concomitantly received methotrexate (MTX) and 63% had previously received anti-tumor necrosis factor (TNF) therapy. Average disease activity score (DAS) 28 of all 229 patients significantly decreased from 5.70 to 3.25 after 24 weeks of therapy. A European League Against Rheumatism (EULAR) good response and DAS28 remission was achieved in 57.4 and 40.7% of the patients, respectively, at 24 weeks. White blood cell counts significantly decreased and liver enzymes and total cholesterol slightly but significantly increased; however, liver enzyme levels did not increase in patients without MTX. Tocilizumab was discontinued in 47 cases (20.5%) due to lack of efficacy (5.2%), adverse events (11.4%), and other reasons (3.9%). The overall retention rate at 24 weeks was 79.5%. Based on these results, we conclude that tocilizumab therapy in daily rheumatology practice appears to be highly efficacious and well tolerated among active RA patients, including the anti-TNF therapy-refractory population. Tocilizumab infusion is therefore applicable not only as an alternative approach for anti-TNF therapy-resistant patients, but also as primary biologic therapy for active RA patients.

The long winding road toward understanding the molecular mechanisms for B-cell suppression by 2,3,7,8-tetrachlorodibenzo-p-dioxin

Suppression of humoral immune responses by 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) was first reported in the mid-1970s. Since this initial observation, much effort has been devoted by many laboratories toward elucidation of the cellular and molecular mechanisms responsible for the profound impairment of humoral immune responses by TCDD, which is characterized by decreased B cell to plasma cell differentiation and suppression of immunoglobulin production. These efforts have led to a significant body of research demonstrating a direct effect of TCDD on B-cell maturation and function as well as a requisite but as yet undefined role of the aryl hydrocarbon receptor (AhR) in these effects. Likewise, a number of molecular targets putatively involved in mediating B-cell dysfunction by TCDD, and other AhR ligands, have been identified. However, our current understanding has primarily relied on findings from mouse models, and the translation of this knowledge to effects on human B cells and humoral immunity in humans is less clear. Therefore, a current challenge is to determine how TCDD and the AhR affect human B cells. Efforts have been made in this direction but continued progress in developing adequate human models is needed. An in-depth discussion of these advances and limitations in elucidating the cellular and molecular mechanisms putatively involved in the suppression of B-cell function by TCDD as well as the implications on human diseases associated in epidemiological studies with exposure to TCDD and dioxin-like compounds is the primary focus of this review.

Interleukin-6: from identification of the cytokine to development of targeted treatments

Interleukin-6 (IL-6) was identified based on extensive research conducted simultaneously on a variety of topics ranging from hepatocyte production of acute-phase proteins to plasmacytoma growth. IL-6 is a cytokine produced by a broad array of cell types and can exert its effects on virtually all cells. IL-6 can induce cell signaling not only via the classic pathway involving the transmembrane receptor IL-6Rα (restricted cellular expression) associated with gp130 (ubiquitous and responsible for signal transmission), but also via the soluble receptor IL-6Rα, which binds to IL-6 and induces a signal mediated by the ubiquitous gp130 molecule (transsignaling). IL-6 is deregulated in many inflammatory and autoimmune diseases, including rheumatoid arthritis (RA). By virtue of its multiple effects, IL-6 is involved in the various phases of RA development, including the acute phase, immuno-inflammatory phase, and destructive phase. IL-6 has an impact on the many pathogenic factors identified in RA and, consequently, holds promise for targeted treatments. However, anti-IL-6 monoclonal antibodies evaluated as IL-6 antagonists, instead, increased the half-life of the cytokine. In contrast, monoclonal antibody (tocilizumab) to transmembrane and soluble IL-6Rα has been found effective in patients with RA. Tocilizumab is now indicated for the treatment of adults with RA who have failed at least one synthetic disease-modifying antirheumatic drug or TNFα antagonist.

Memory B cells from older people express normal levels of cyclooxygenase-2 and produce higher levels of IL-6 and IL-10 upon in vitro activation

Worldwide the elderly population is increasing. The elderly show deficiencies in immune function. B lymphocytes are essential elements of the immune system responsible for antibody production. This laboratory previously showed that activated human B cells isolated from young adults express cyclooxygenase-2 (Cox-2) and that Cox-2 is essential for optimal antibody responses. Recent data suggests that Cox-2 expression decreases with age in mouse bone tissue. There is no information regarding Cox-2 expression in B cells from older human subjects. We investigated the expression and activity of Cox-2 in naïve and memory B cells from older people. We show that B cells from older subjects show similar Cox-2 protein expression and activity, antibody production and proliferation compared to younger people. However, we found that activated memory B cells from older people produce higher levels of IL-6 and IL-10 compared to young adults. Therefore, the dysregulated cytokine production could contribute to immune senescence in the elderly.

Distinct patterns of DNA damage response and apoptosis correlate with Jak/Stat and PI3kinase response profiles in human acute myelogenous leukemia

Background

Single cell network profiling (SCNP) utilizing flow cytometry measures alterations in intracellular signaling responses. Here SCNP was used to characterize Acute Myeloid Leukemia (AML) disease subtypes based on survival, DNA damage response and apoptosis pathways.

Methodology and Principal Findings

Thirty four diagnostic non-M3 AML samples from patients with known clinical outcome were treated with a panel of myeloid growth factors and cytokines, as well as with apoptosis-inducing agents. Analysis of induced Jak/Stat and PI3K pathway responses in blasts from individual patient samples identified subgroups with distinct signaling profiles that were not seen in the absence of a modulator. In vitro exposure of patient samples to etoposide, a DNA damaging agent, revealed three distinct “DNA damage response (DDR)/apoptosis” profiles: 1) AML blasts with a defective DDR and failure to undergo apoptosis; 2) AML blasts with proficient DDR and failure to undergo apoptosis; 3) AML blasts with proficiency in both DDR and apoptosis pathways. Notably, AML samples from clinical responders fell within the “DDR/apoptosis” proficient profile and, as well, had low PI3K and Jak/Stat signaling responses. In contrast, samples from clinical non responders had variable signaling profiles often with in vitro apoptotic failure and elevated PI3K pathway activity. Individual patient samples often harbored multiple, distinct, leukemia-associated cell populations identifiable by their surface marker expression, functional performance of signaling pathway in the face of cytokine or growth factor stimulation, as well as their response to apoptosis-inducing agents.

Conclusions and Significance

Characterizing and tracking changes in intracellular pathway profiles in cell subpopulations both at baseline and under therapeutic pressure will likely have important clinical applications, potentially informing the selection of beneficial targeted agents, used either alone or in combination with chemotherapy.

Altered Toll-like receptor signaling pathways in human type 1 diabetes

There is compelling evidence from animal models of type 1 diabetes (T1D) that the innate immune system plays a key role in early mechanisms triggering islet destruction. Very little is known, however, about innate immune subsets and pathways potentially involved in mechanisms leading to human T1D. The present study used a comprehensive approach to analyze innate immune functions in primary monocytes and dendritic cells (DCs) from newly diagnosed patients with T1D versus age-matched healthy individuals. We observed that incubation of PBMCs in the presence of the TLR7/8 agonist R848 led to increased proportion of plasmacytoid dendritic cells (pDCs) expressing IFN-α in patients versus healthy control subjects. We also found that TLR4 activation induced a higher frequency of IL-1β expressing monocytes and a reduction in the percentage of IL-6 expressing myeloid dendritic cells (mDCs). The altered TLR responsiveness was not due to aberrant proportions of peripheral DC subsets and monocytes in the blood and did not correlate with altered hemoglobin A1c and the expression of diabetes susceptibility genes but could potentially be associated with enhanced nuclear factor-kappa B signaling. Finally, we observed that levels of serum IFN-α2, IL-1β, IFN-γ, and CXCL-10 were elevated in new onset patients versus the control group. Taken together, our observations provide evidence that altered innate immunity exists in mDCs and pDCs from T1D and raise the possibility that these alterations may be associated with disease mechanisms.

Infection with the intracellular bacterium, Listeria monocytogenes, overrides established tolerance in a mouse cardiac allograft model

Infections and TLR signals at the time of transplantation have been shown to prevent the induction of tolerance, but their effect on allografts after tolerance has been established is unclear. We here report that infection with Listeria monocytogenes precipitated the loss of tolerance and the MyD88- and T cell-dependent rejection of accepted cardiac allografts in mice. This loss of tolerance was associated with increases in the numbers of graft-infiltrating macrophages and dendritic cells, as well as CD4(+)FoxP3(-) and CD8(+) T cells. Rejection was also associated with increased numbers of graft-infiltrating alloreactive as well as Listeria-reactive IFNgamma-producing T cells. Rejection of the established grafts required both IL-6 and IFNss, cytokines produced during acute Listeria infection. However, IL-6 and IFNss alone, even when present at higher concentrations than during Listeria infection, were insufficient to break tolerance, while the combination of IL-6 and IFNss was sufficient to break tolerance. These and in vitro observations that IL-6 but not IFNss enhanced T cell proliferation while IFNss but not IL-6 enhanced IFNgamma production support a hypothesis that these cytokines play nonredundant roles. In conclusion, these studies demonstrate that the proinflammatory effects of infections can induce the loss of tolerance and acute rejection of accepted allografts.

A gain of function polymorphism in the interleukin 6 receptor influences RA susceptibility

OBJECTIVES

To investigate the possible role of a functional polymorphism in the soluble interleukin 6 receptor (sIL-6R) gene in the genetic background of rheumatoid arthritis (RA).

METHODS

An association between disease status and the sIL-6R rs8192284 (A358D) variant was tested in 965 patients with RA and 988 unrelated healthy controls. Odds ratios (ORs) for disease were calculated with asymptotic 95% CI; p values <0.05 were considered statistically significant after adjustment for multiple testing. To determine the relationship between protein levels and IL-6R A358D genotype, the protein levels of sIL-6R in 100 plasma samples from healthy controls were measured using an ELISA and compared across the genotype groups.

RESULTS

The allele frequency of the C allele (alanine) was lower in cases than in controls (38.4% vs 41.7%, p=0.04, OR 0.9, 95% CI 0.8 to 1.0), as were the CC/AC genotypes compared with AA genotype frequencies (61.0% in RA cases vs 67.5% in controls, p=0.004, OR 0.8, 95% CI 0.6 to 0.9). Plasma levels of sIL-6R differed significantly according to genotype in the controls: 17.00 + or - 2.03 ng/ml for A/A, 20.08 + or - 1.83 ng/ml for A/C and 21.57 + or - 2.10 ng/ml for C/C (p=0.0001).

CONCLUSION

These data suggest a role for genetically determined lower sIL-6R levels as a risk factor for RA. The proinflammatory role of the IL6 system in established RA has been highlighted by the use of anti-sIL-6R antibodies. However, the findings of this study suggest a protective effect of IL6 on the risk of developing RA.

Phospholipase D1 mediates TNFalpha-induced inflammation in a murine model of TNFalpha-induced peritonitis

Background

Tumor Necrosis Factor alpha (TNFα) is a pleiotropic cytokine extensively studied for its role in the pathogenesis of a variety of disease conditions, including in inflammatory diseases. We have recently shown that, in vitro, that TNFα utilizes PLD1 to mediate the activation of NFκB and ERK1/2 in human monocytes. The aim of this study was to investigate the role(s) played by phospholipase D1 (PLD1) in TNFα-mediated inflammatory responses in vivo.

Methodology/Findings

Studies were performed in vivo using a mouse model of TNFα-induced peritonitis. The role of PLD1 was investigated by functional genomics, utilizing a specific siRNA to silence the expression of PLD1. Administration of the siRNA against PLD1 significantly reduced PLD1 levels in vivo. TNFα triggers a rapid pyrogenic response, but the in vivo silencing of PLD1 protects mice from the TNFα-induced rise in temperature. Similarly TNFα caused an increase in the serum levels of IL-6, MIP-1α and MIP-1β: this increase in cytokine/chemokine levels was inhibited in mice where PLD1 had been silenced. We then induced acute peritonitis with TNFα. Intraperitoneal injection of TNFα triggered a rapid increase in vascular permeability, and the influx of neutrophils and monocytes into the peritoneal cavity. By contrast, in mice where PLD1 had been silenced, the TNFα-triggered increase in vascular permeability and phagocyte influx was substantially reduced. Furthermore, we also show that the TNFα-mediated upregulation of the cell adhesion molecules VCAM and ICAM1, in the vascular endothelium, were dependent on PLD1.

Conclusions

These novel data demonstrate a critical role for PLD1 in TNFα-induced inflammation in vivo and warrant further investigation. Indeed, our results suggest PLD1 as a novel target for treating inflammatory diseases, where TNFα play key roles: these include diseases ranging from sepsis to respiratory and autoimmune diseases; all diseases with considerable unmet medical need.

Cytokines as therapeutic targets in SLE

Systemic lupus erythematosus (SLE) is a heterogeneous autoimmune disease involving most immune cells. Studies in both experimental animal models of lupus and patients with SLE have revealed a number of cytokine pathways that are important in the disease process. Among these are B-cell activating factor, which promotes B-cell survival and autoantibody production, interferon-alpha, which acts as an immune adjuvant, and tumor necrosis factor, which contributes to organ inflammation. This knowledge, in combination with the successful use of anti-TNF treatment in rheumatoid arthritis, has spurred the development of several biologic agents targeting different cytokines or their receptors in SLE. Consequently, many trials of anticytokine therapies for SLE are underway. Although most of these trials are small or in early phases, the results of some large studies have also been reported. In this Review, we discuss the rationale for anticytokine therapies in SLE and review agents currently in use, and those being developed and tested experimentally. We present the results from published trials and discuss the tentative conclusions that can be drawn regarding the efficacy of the new agents. Finally, we provide suggestions for the future of treatment for SLE, including new therapeutic strategies.

Role for interleukin-6 in structural joint damage and systemic bone loss in rheumatoid arthritis

Interleukin-6 (IL-6) plays a key role in the local and systemic manifestations of rheumatoid arthritis (RA). IL-6 is not only a proinflammatory cytokine, but also interacts in complex ways with the cells involved in bone remodeling. In RA, IL-6 may indirectly promote osteoclastogenesis by increasing the release of RANK-L by osteoblasts and synovial cells. However, IL-6 inhibits osteoclastogenesis in vitro, via a direct mechanism. The effects of IL-6 on osteoblasts may vary with the cell differentiation stage: thus, IL-6 may promote the differentiation of pre-osteoblasts to mature osteoblasts while also diminishing the proliferation of osteoblasts at late differentiation stages. Thus, the effects of IL-6 on bone remodeling are complex and may occur in opposite directions depending on the model or experimental conditions. Nevertheless, results from studies in animal models and humans support a negative effect of IL-6 on bone. Thus, in patients with RA, blocking IL-6 may be effective both in diminishing the inflammatory manifestations and in preventing the bone complications of the disease.

IL-6 and high glucose synergistically upregulate MMP-1 expression by U937 mononuclear phagocytes via ERK1/2 and JNK pathways and c-Jun

Matrix metalloproteinases (MMPs) play a pivotal role in tissue remodeling and destruction in inflammation-associated diseases such as cardiovascular disease and periodontal disease. Although it is known that interleukin (IL)-6 is a key proinflamatory cytokine, it remains unclear how IL-6 regulates MMP expression by mononuclear phagocytes. Furthermore, it remains undetermined how IL-6 in combination with hyperglycemia affects MMP expression. In the present study, we investigated the regulatory effect of IL-6 alone or in combination with high glucose on MMP-1 expression by U937 mononuclear phagocytes. We found that IL-6 is a powerful stimulator for MMP-1 expression and high glucose further augmented IL-6-stimulated MMP-1 expression. We also found that high glucose, IL-6, and lipopolysaccharide act in concert to stimulate MMP-1 expression. In the studies to elucidate underlying mechanisms, the extracellular signal-regulated kinase (ERK) and c-Jun N-terminal kinase (JNK) pathways were found to be required for stimulation of MMP-1 by IL-6 and high glucose. We also observed that IL-6 and high glucose stimulated the expression of c-Jun, a key subunit of AP-1 known to be essential for MMP-1 transcription. The role of c-Jun in MMP-1 expression was confirmed by the finding that suppression of c-Jun expression by RNA interference significantly inhibited MMP-1 expression. Finally, we demonstrated that similarly to U937 mononuclear phagocytes, IL-6 and high glucose also stimulated MMP-1 secretion from human primary monocytes. In conclusion, this study demonstrated that IL-6 and high glucose synergistically stimulated MMP-1 expression in mononuclear phagocytes via ERK and JNK cascades and c-Jun upregulation.

Array-based transcript profiling and limiting-dilution reverse transcription-PCR analysis identify additional latent genes in Kaposi's sarcoma-associated herpesvirus

Kaposi's sarcoma-associated herpesvirus (KSHV) is a B-lymphotropic herpesvirus strongly linked to both lymphoproliferative diseases and Kaposi's sarcoma. The viral latency program of KSHV is central to persistent infection and plays important roles in the pathogenesis of KSHV-related tumors. Up to six polypeptides and 18 microRNAs are known to be expressed in latency, but it is unclear if all major latency genes have been identified. Here, we have employed array-based transcript profiling and limiting-dilution reverse transcription-PCR (RT-PCR) methodologies to explore this issue in several KSHV-infected cell lines. Our results show that RNAs encoding the K1 protein are found at low levels in most latently infected cell lines. The gene encoding v-IL-6 is also expressed as a latent transcript in some contexts. Both genes encode powerful signaling molecules with particular relevance to B cell biology: K1 mimics signaling through the B cell receptor, and v-IL-6 promotes B cell survival. These data resolve earlier controversies about K1 and v-IL-6 expression and indicate that, in addition to core latency genes, some transcripts can be expressed in KSHV latency in a context-dependent manner.

Interleukin-6 polymorphisms modify the risk of periodontitis: a systematic review and meta-analysis

OBJECTIVE

To clarify the association of IL-6 polymorphisms and periodontitis, a meta-analysis of case-control studies and a systemic review were conducted.

MATERIAL AND METHODS

We performed a literature search using PubMed and Medline database to May 2009, with no restrictions. We also reviewed references from all retrieved articles. Six case-control studies involving 1 093 periodontitis cases and 574 controls were selected for meta-analysis to assess the purported associations between IL-6 polymorphisms and the risk of periodontitis. IL-6 -174 G/C and -572 C/G polymorphisms were included in the present meta-analysis, and the association between IL-6 -6331 T/C polymorphism and the risk of periodontitis was adequately reviewed as well.

RESULTS AND CONCLUSION

The present meta-analysis indicates that the IL-6 -174 G allele could not modify the risk of chronic periodontitis, but increased the risk of aggressive periodontitis. And -572 C/G polymorphism is associated with the pathogenesis of periodontitis, including chronic periodontitis or aggressive periodontitis.

Predominant inflammatory cytokine secretion pattern in response to two doses of live rubella vaccine in healthy vaccinees

We conducted a population-based study on 738 schoolchildren who received two doses of rubella vaccine in order to determine cytokine secretion patterns and their associations with demographic and clinical variables. The results showed a robust rubella-specific inflammatory cytokine response characterized by high median [inter-quartile range (IQR)] secretion levels (in pg/mL) of IL-6 [3681.0 (3160.0, 4052.0)], GM-CSF [28.0 (23.6, 32.6)], and TNF-alpha [29.7 (-7.0, 89.2)]. We also detected modest levels of rubella-specific secretion of Th1 cytokines IL-2 and IFN-gamma, while IL-12p40 was undetectable. In contrast, rubella-specific Th2 responses were hardly detectable. Age at vaccination, enrollment, and time elapsed between last vaccination and enrollment was significantly associated with the outcome of IL-2, IL-6, and IFN-gamma secretion. These results suggest an immune-deviation or "skewing" from Th1/Th2 cytokine patterns towards a predominant inflammatory response upon in vitro rubella virus stimulation.

A bovine whey protein extract stimulates human neutrophils to generate bioactive IL-1Ra through a NF-kappaB- and MAPK-dependent mechanism

Innate immunity depends on the efficiency of neutrophils to be activated rapidly to restore homeostasis. It can benefit from priming agents that enhance neutrophil capacity to respond more efficiently to a subsequent stimulation. Among natural products, a bovine whey protein extract (WPE) has been shown to prime normal human blood neutrophils by enhancing their chemotaxis, phagocytosis, oxidative burst, and degranulation. These leukocytes are also an important source of cytokines, some of which have antiinflammatory functions. We investigated the role of WPE, as well as its mechanisms of action, on the production of interleukin (IL)-1 receptor antagonist (IL-1Ra) by neutrophils in vitro. WPE dose-dependently stimulated de novo synthesis and release of IL-1Ra by normal human blood neutrophils. Among the major proteins present in WPE, beta-lactoglobulin (beta-LG) and alpha-lactalbumin (alpha-LA) were the only active components. They had additive effects that exactly reproduced those of WPE. Similarly to WPE, they also stimulated the accumulation of IL-1beta, IL-8, IL-6, macrophage inflammatory protein (MIP)-1alpha, MIP-1beta, and tumor necrosis factor-alpha. However, neutrophils incubated with WPE, beta-LG, and alpha-LA produced IL-1Ra in excess of IL-1beta and the ratio IL-1Ra:IL-1beta increased linearly. The amounts of IL-1Ra stimulated by WPE or beta-LG + alpha-LA significantly reduced the IL-1 activity in EL4 cells. Inhibitors of p38 and extracellular signal-regulated kinases (ERK)1/2 mitogen-activated protein kinase, and nuclear factor-kappaB cascades reduced neutrophil production of IL-1Ra. Our data suggest that WPE, through beta-LG + alpha-LA, has immunomodulatory properties and the potential to increase host defenses.

Rubella vaccine-induced cellular immunity: evidence of associations with polymorphisms in the Toll-like, vitamin A and D receptors, and innate immune response genes

Toll-like, vitamin A and D receptors and other innate proteins participate in various immune functions. We determined whether innate gene-sequence variations are associated with rubella vaccine-induced cytokine immune responses. We genotyped 714 healthy children (11-19 years of age) after two doses of rubella-containing vaccine for 148 candidate SNP markers. Rubella virus-induced cytokines were measured by ELISA. Twenty-two significant associations (range of P values 0.002-0.048) were found between SNPs in the vitamin A receptor family (RARA, RARB, TOP2B and RARG), vitamin D receptor and downstream mediator of vitamin D signaling (RXRA) genes and rubella virus-specific (IFN-gamma, IL-2, IL-10, TNF-alpha, and GM-CSF) cytokine immune responses. A TLR3 gene promoter region SNP (rs5743305, -8441A > T) was associated with rubella-specific GM-CSF secretion. Importantly, SNPs in the TRIM5 gene coding regions, rs3740996 (His43Tyr) and rs10838525 (Gln136Arg), were associated with an allele dose-related secretion of rubella virus-specific TNF-alpha and IL-2/GM-CSF, respectively, and have been previously shown to have functional consequences regarding the antiviral activity and susceptibility to HIV-1 infection. We identified associations between individual SNPs and haplotypes in, or involving, the RIG-I (DDX58) gene and rubella-specific TNF-alpha secretion. This is the first paper to present evidence that polymorphisms in the TLR, vitamin A, vitamin D receptor, and innate immunity genes can influence adaptive cytokine responses to rubella vaccination.

Comparison of tocilizumab monotherapy versus methotrexate monotherapy in patients with moderate to severe rheumatoid arthritis: the AMBITION study

BACKGROUND

The anti-interleukin (IL) 6 receptor antibody tocilizumab inhibits signalling of IL6, a key cytokine in rheumatoid arthritis (RA) pathogenesis.

OBJECTIVE

To evaluate through the AMBITION study the efficacy and safety of tocilizumab monotherapy versus methotrexate in patients with active RA for whom previous treatment with methotrexate/biological agents had not failed.

METHODS

This 24-week, double-blind, double-dummy, parallel-group study, randomised 673 patients to either tocilizumab 8 mg/kg every 4 weeks, or methotrexate, starting at 7.5 mg/week and titrated to 20 mg/week within 8 weeks, or placebo for 8 weeks followed by tocilizumab 8 mg/kg. The primary end point was the proportion of patients achieving American College of Rheumatology (ACR) 20 response at week 24.

RESULTS

The intention-to-treat analysis demonstrated that tocilizumab was better than methotrexate treatment with a higher ACR20 response (69.9 vs 52.5%; p<0.001), and 28-joint Disease Activity Score (DAS28) <2.6 rate (33.6 vs 12.1%) at week 24. Mean high-sensitivity C-reactive protein was within the normal range from week 12 with tocilizumab, whereas levels remained elevated with methotrexate. The incidence of serious adverse events with tocilizumab was 3.8% versus 2.8% with methotrexate (p = 0.50), and of serious infections, 1.4% versus 0.7%, respectively. There was a higher incidence of reversible grade 3 neutropenia (3.1% vs 0.4%) and increased total cholesterol > or =240 mg/dl (13.2% vs 0.4%), and a lower incidence of alanine aminotransferase elevations >3x-<5x upper limit of normal (1.0% vs 2.5%), respectively.

CONCLUSION

Tocilizumab monotherapy is better than methotrexate monotherapy, with rapid improvement in RA signs and symptoms, and a favourable benefit-risk, in patients for whom treatment with methotrexate or biological agents has not previously failed.

Autoimmune disease in Lyn-deficient mice is dependent on an inflammatory environment established by IL-6

Lyn-deficient mice develop Ab-mediated autoimmune disease resembling systemic lupus erythematosus where hyperactive B cells are major contributors to pathology. In this study, we show that an inflammatory environment is established in Lyn(-/-) mice that perturbs several immune cell compartments and drives autoimmune disease. Lyn(-/-) leukocytes, notably B cells, are able to produce IL-6, which facilitates hyperactivation of B and T cells, enhanced myelopoiesis, splenomegaly, and, ultimately, generation of pathogenic autoreactive Abs. Lyn(-/-) dendritic cells show increased maturation, but this phenotype is independent of autoimmunity as it is reiterated in B cell-deficient Lyn(-/-) mice. Genetic deletion of IL-6 on a Lyn-deficient background does not alter B cell development, plasma cell accumulation, or dendritic cell hypermaturation, suggesting that these characteristics are intrinsic to the loss of Lyn. However, hyperactivation of B and T cell compartments, extramedullary hematopoiesis, expansion of the myeloid lineage and autoimmune disease are all ameliorated in Lyn(-/-)IL-6(-/-) mice. Importantly, our studies show that although Lyn(-/-) B cells may be autoreactive, it is the IL-6-dependent inflammatory environment they engender that dictates their disease-causing potential. These findings improve our understanding of the mode of action of anti-IL-6 and B cell-directed therapies in autoimmune and inflammatory disease treatment.

Adipocyte-mononuclear cell interaction, Toll-like receptor 4 activation, and high glucose synergistically up-regulate osteopontin expression via an interleukin 6-mediated mechanism

Although it has been reported that osteopontin, a matrix glycoprotein and proinflammatory cytokine, mediates obesity-induced adipose tissue macrophage infiltration and insulin resistance, it remains unclear how osteopontin is up-regulated in adipose tissue in obese humans and animals. In this study, we incubated U937 mononuclear cells with adipocytes in a transwell system and studied how cell interaction regulated osteopontin expression. Results showed that coculture of U937 cells with adipocytes led to a marked increase in osteopontin production when compared with that released by independent cultures of U937 cells. Moreover, lipopolysaccharide or palmitic acid-induced TLR4 activation and high glucose further augmented the coculture-stimulated osteopontin secretion. Similar observations were made in the coculture of human primary monocytes and adipocytes. Real time PCR studies showed that coculture of U937 cells and adipocytes increased osteopontin mRNA in U937 cells, but not adipocytes, suggesting that adipocyte-derived soluble factor may stimulate osteopontin expression by U937 cells. In our studies to explore the underlying mechanism, we found that the neutralizing antibodies against interleukin (IL)-6 or IL-6 small interfering RNA transfection in adipocytes effectively inhibited coculture-stimulated osteopontin expression, suggesting that IL-6 released by adipocytes plays an essential role in the coculture-stimulated osteopontin expression by U937 cells. In conclusion, this study has demonstrated that cell interaction, TLR4 activation, and high glucose up-regulate osteopontin expression, and adipocyte-derived IL-6 played a major role in the up-regulation.

Adjuvant effects for oral immunization provided by recombinant Lactobacillus casei secreting biologically active murine interleukin-1{beta}

Vaccine delivery systems using lactic acid bacteria are under development, but their efficiency is insufficient. Autologous cytokines, such as interleukin-1beta (IL-1beta), are potential adjuvants for mucosal vaccines and can be provided by recombinant lactic acid bacteria. The aim of this study was the construction and evaluation of recombinant Lactobacillus casei producing IL-1beta as an adjuvant delivery agent. The recombinant strain was constructed using an expression/secretion vector plasmid, including a mature IL-1beta gene from mouse. The biological activity of the cytokine was confirmed by IL-8 production from Caco-2 cells. In response to the recombinant L. casei secreting IL-1beta, expression of IL-6 was detected in vivo using a ligated-intestinal-loop assay. The release of IL-6 from Peyer's patch cells was also detected in vitro. Intragastric immunization with heat-killed Salmonella enterica serovar Enteritidis (SE) in combination with IL-1beta-secreting lactobacilli resulted in relatively high SE-specific antibody production. In this study, it was demonstrated that recombinant L. casei secreting bioactive murine IL-1beta provided adjuvant effects for intragastric immunization.

Hop bitter acids efficiently block inflammation independent of GRalpha, PPARalpha, or PPARgamma

Hop (Humulus lupulus L.) is an essential ingredient of beer, where it provides the typical bitter taste, but is also applied in traditional folk medicine for sedative and antibacterial purposes. In this study, we demonstrate and compare the anti-inflammatory effect of various classes of hop bitter acids (HBA), including alpha-acids (AA), beta-acids (BA), and iso-alpha-acids (IAA), in fibroblasts, which are important players in the inflammatory response. All three studied classes of HBA blocked the tumor necrosis factor alpha (TNF)-induced production of the cytokine IL6, and inhibited the transactivation of the pro-inflammatory transcription factors nuclear factor kappa B (NF-kappaB), activator protein-1 (AP-1), and cAMP-response element-binding protein (CREB). In this respect, the six-membered ring compounds AA and BA showed equal potency, whereas the five-membered ring compounds, IAA, were effective only when used at higher concentrations. Furthermore, with regard to the mechanism of NF-kappaB suppression, we excluded a possible role for glucocorticoid receptor alpha (GRalpha), peroxisome proliferators-activated receptor alpha/gamma (PPARalpha or PPARgamma), nuclear receptors (NRs) that are also known to inhibit inflammation by directly interfering with the activity of pro-inflammatory transcription factors. Interestingly, combining hop acids and selective agonists for GRalpha, PPARalpha, or PPARgamma resulted in additive inhibition of NF-kappaB activity after TNF treatment, which may open up new avenues for combinatorial anti-inflammatory strategies with fewer side effects. Finally, systemic administration of HBA efficiently inhibited acute local inflammation in vivo.

Recent advances in neutralizing the IL-6 pathway in arthritis

Recent advances in understanding the mechanism(s) of how IL-6 trans-signaling regulates immune cell function and promotes inflammation in autoimmune arthritis are critically reviewed. Serum and/or synovial fluid (SF) IL-6 is markedly elevated in adult and juvenile rheumatoid arthritis (RA), psoriatic arthritis (PsA), ankylosing spondylitis (AS) and osteoarthritis (OA). IL-6, in concert with IL-17, determines the fate of CD4⁺ lymphocytes and therefore TH₁₇ cell differentiation. IL-6 also plays a critical role in modulating B-lymphocyte activity. The recognition that IL-6 trans-signaling regulates inflammation resulted in the development of tocilizumab, a fully humanized monoclonal antibody that neutralizes the biological activity of the IL-6-receptor (IL-6R). Significant clinical benefit was demonstrated as well as reduced serum IL-6 levels with suppression of X-ray progression of disease in several clinical trials in which juvenile or adult RA patients were treated with tocilizumab monotherapy or tocilizumab plus methotrexate. However, levels of serum and/or SF IL-6 cytokine protein superfamily members, adiponectin, oncostatin M, pre-B-cell colony enhancing factor/visfatin and leukemia inhibitory factor are also elevated in RA. Additional studies will be required to determine if anti-IL-6 trans-signaling inhibition strategies with tocilizumab or recombinant soluble IL-6R reduce the level of these cytokines.

Interleukin-6 subfamily cytokines and rheumatoid arthritis: role of antagonists

Many cytokines have been implicated in the inflammatory pathways that characterize rheumatoid arthritis (RA) and related inflammatory diseases of the joints. These include members of the interleukin-6 (IL-6) family of cytokines, several of which have been detected in excess in the synovial fluid from RA patients. What makes the IL-6 group of cytokines a family is their common use of the glycoprotein 130 (gp130) receptor subunit, to which they bind with different affinities. Several strategies have been developed to block the pro-inflammatory activities of IL-6 subfamily cytokines. These include the application of monoclonal antibodies, the creation of mutant form(s) of the cytokine with enhanced binding affinity to gp130 receptor and the generation of antagonists by selective mutagenesis of the specific cytokine/gp130 receptor-binding site(s). The rationale for the use of anti-cytokine therapy in inflammatory joint diseases is based on evidence from studies in vitro and in vivo, which implicate major cytokines such as interleukin-1 (IL-1), tumour necrosis factor (TNF)-alpha and IL-6 in RA pathogenesis. In particular, IL-6 subfamily antagonists have a wide range of potential therapeutic and research applications. This review focuses on the role of some of the IL-6 subfamily cytokines in the pathogenesis of the inflammatory diseases of the joints (IJDs), such as RA. In addition, an overview of the recently developed antagonists will be discussed.

Endotoxin-induced translocation of interleukin-6 from lungs to the systemic circulation

It is widely postulated that systemic inflammation related to lung infections is largely caused by cytokine translocation from the lungs into the systemic circulation but there is a paucity of animal models to evaluate this hypothesis. In this proof-of-concept study, we developed a murine model to determine whether interleukin (IL)-6, a primary inflammatory cytokine, translocates following airway exposure to endotoxin. We collected central venous blood from the right atrium and arterial blood from the aorta simultaneously at 4 h and 24 h following intratracheal exposure to endotoxin (25 microg) and measured IL-6 in the serum and broncho-alveolar lavage (BAL) fluid (n = 33 mice). We repeated the experiment following 3 d of treatment with dexamethasone (n = 31 mice). Without stimulation, there was no significant arteriovenous gradient (3 pg/ml with interquartile range [IQR] of 3-5 pg/ml in arterial versus 18 pg/ml with IQR of 8-24 pg/ml in venous serum; P = 0.86). A significant arteriovenous difference was observed by 4 h post-exposure to endotoxin (2813 pg/ml with IQR of 1578-4316 pg/ml in arterial versus 1282 pg/ml with IQR of 778-2699 pg/ml in venous serum; P50.0001). The rise in the BAL IL-6 levels correlated with the increases in the arterial serum levels (P50.0001). Administration of intraperitoneal dexamethasone for 3 d attenuated the increased arteriovenous gradient. This murine model facilitates the estimation of cytokine translocation across the lungs and evaluation of compounds to modulate this gradient.

Maternal exposure to secondhand cigarette smoke primes the lung for induction of phosphodiesterase-4D5 isozyme and exacerbated Th2 responses: rolipram attenuates the airway hyperreactivity and muscarinic receptor expression but not lung inflammation and atopy

Airway hyperreactivity (AHR), lung inflammation, and atopy are clinical signs of allergic asthma. Gestational exposure to cigarette smoke (CS) markedly increases the risk for childhood allergic asthma. Muscarinic receptors regulate airway smooth muscle tone, and asthmatics exhibit increased AHR to muscarinic agonists. We have previously reported that in a murine model of bronchopulmonary aspergillosis, maternal exposure to mainstream CS increases AHR after acute intratracheal administration of Aspergillus fumigatus extract. However, the mechanism by which gestational CS induces allergic asthma is unclear. We now show for the first time that, compared with controls, mice exposed prenatally to secondhand CS exhibit increased lung inflammation (predominant infiltration by eosinophils and polymorphs), atopy, and airway resistance, and produce proinflammatory cytokines (IL-4, IL-5, IL-6, and IL-13, but not IL-2 or IFN-gamma). These changes, which occur only after an allergen (A. fumigatus extract) treatment, are correlated with marked up-regulated lung expression of M1, M2, and M3 muscarinic receptors and phosphodiesterase (PDE)4D5 isozyme. Interestingly, the PDE4-selective inhibitor rolipram attenuates the increase in AHR, muscarinic receptors, and PDE4D5, but fails to down-regulate lung inflammation, Th2 cytokines, or serum IgE levels. Thus, the fetus is extraordinarily sensitive to CS, inducing allergic asthma after postnatal exposure to allergens. Although the increased AHR might reflect increased PDE4D5 and muscarinic receptor expression, the mechanisms underlying atopy and lung inflammation are unrelated to the PDE4 activity. Thus, PDE4 inhibitors might ease AHR, but are unlikely to attenuate lung inflammation and atopy associated with childhood allergic asthma.

A unifying model for the selective regulation of inducible transcription by CpG islands and nucleosome remodeling

We describe a broad mechanistic framework for the transcriptional induction of mammalian primary response genes by Toll-like receptors and other stimuli. One major class of primary response genes is characterized by CpG-island promoters, which facilitate promiscuous induction from constitutively active chromatin without a requirement for SWI/SNF nucleosome remodeling complexes. The low nucleosome occupancy at promoters in this class can be attributed to the assembly of CpG islands into unstable nucleosomes, which may lead to SWI/SNF independence. Another major class consists of non-CpG-island promoters that assemble into stable nucleosomes, resulting in SWI/SNF dependence and a requirement for transcription factors that promote selective nucleosome remodeling. Some stimuli, including serum and tumor necrosis factor-alpha, exhibit a strong bias toward activation of SWI/SNF-independent CpG-island genes. In contrast, interferon-beta is strongly biased toward SWI/SNF-dependent non-CpG-island genes. By activating a diverse set of transcription factors, Toll-like receptors induce both classes and others for an optimal response to microbial pathogens.

Japan College of Rheumatology 2009 guidelines for the use of tocilizumab, a humanized anti-interleukin-6 receptor monoclonal antibody, in rheumatoid arthritis

The introduction of biological agents targeting tumor necrosis factor-alpha (TNF-alpha) has brought about a paradigm shift in the treatment of rheumatoid arthritis (RA). Although these anti-TNF agents have excellent efficacy against RA, a substantial number of patients still show inadequate responses. In Western countries, such patients are already being treated with new classes of antirheumatic drugs such as abatacept and rituximab. Tocilizumab (TCZ) is a humanized monoclonal antibody developed in Japan against the human interleukin-6 (IL-6) receptor. TCZ does not only alleviate the signs and symptoms of RA but also seems to prevent progressive bone and joint destruction. However, there is a concern that TCZ might increase the risk of adverse events such as infections since IL-6 plays a pivotal role in the immune system. Calculating the relative risks of specific adverse outcomes with TCZ use remains difficult, due to insufficient patient numbers enrolled in clinical trials to date. This review presents tentative guidelines for the use of TCZ for RA patients prepared by the Japan College of Rheumatology and based on results of clinical trials in Japan and Western countries. The guidelines are intended as a guide for postmarketing surveillance and clinical practice, and will be revised periodically based on the surveillance.

Interleukin-6 induces an epithelial-mesenchymal transition phenotype in human breast cancer cells

Breast tumor interleukin-6 (IL-6) levels increase with tumor grade, and elevated serum IL-6 correlates with poor breast cancer patient survival. Epithelial-mesenchymal transition (EMT) phenotypes such as impaired E-cadherin expression or aberrant Vimentin induction are associated with enhanced metastasis and unfavorable clinical outcome in breast cancer. Despite this fact, few tumor microenvironment-derived extracellular signaling factors capable of provoking such a phenotypic transition have been identified. In this study, we showed that IL-6 promoted E-cadherin repression among a panel of estrogen receptor-alpha-positive human breast cancer cells. Furthermore, ectopic stable IL-6 expressing MCF-7 breast adenocarcinoma cells (MCF-7(IL-6)) exhibited an EMT phenotype characterized by impaired E-cadherin expression and induction of Vimentin, N-cadherin, Snail and Twist. MCF-7(IL-6) cells formed xenograft tumors that displayed loss of E-cadherin, robust Vimentin induction, increased proliferative indices, advanced tumor grade and undifferentiated histology. Finally, we showed aberrant IL-6 production and STAT3 activation in MCF-7 cells that constitutively express Twist, a metastatic regulator and direct transcriptional repressor of E-cadherin. To our knowledge, this is the first study that shows IL-6 as an inducer of an EMT phenotype in breast cancer cells and implicates its potential to promote breast cancer metastasis.

Mechanisms for suppression of interleukin-6 expression in peritoneal macrophages from docosahexaenoic acid-fed mice

Consumption of the trichothecene mycotoxin deoxynivalenol (DON) induces interleukin-6 (IL-6)-dependent IgA nephropathy (IgAN) in mice. This effect can be prevented by feeding long-chain n-3 polyunsaturated fatty acids (PUFAs) found in fish oil. The purpose of this study was to identify the signal transduction pathways by which DON up-regulates IL-6 in the peritoneal macrophage and how consumption of fish oil enriched with the n-3 PUFA docosahexaenoic acid (DHA) suppresses these processes. Incubation with DON induced IL-6 expression in naïve macrophages maximally at 3 h. Knockdown of the transcription factor cAMP response element-binding protein (CREB) or pharmacologic inhibition of the CREB kinases Akt1/2, MSK1 and RSK1 down-regulated this expression. Inhibition of double-stranded RNA-activated protein kinase (PKR) suppressed not only IL-6 expression but also phosphorylation of CREB and its upstream kinases, Akt1, MSK1 and RSK1. Phosphorylations of PKR, CREB kinases and CREB were markedly impaired in peritoneal macrophages isolated from mice that consumed DHA-enriched fish oil for 6 to 8 weeks. DHA's effects were not explainable by increased activity of protein phosphatase 1 and 2A since both were suppressed in mice consuming the DHA diet. Although cells cultured directly with DHA expressed less IL-6 compared to cells cultured with arachidonic acid (AA), neither fatty acid treatment affected DON-induced protein phosphorylation. Furthermore, DHA and AA similarly inhibited cell-free protein kinase activity. These data suggest that DON-induced IL-6 expression is CREB mediated and PKR dependent, and that requisite kinase activities for these pathways were suppressed in macrophages from mice fed DHA for an extended period.

HBV replication is significantly reduced by IL-6

Interleukin-6 (IL-6) is a pleiotropic cytokine with pivotal functions in the regulation of the biological responses of several target cells including hepatocytes. The level of serum IL-6 has been reported to be elevated in patients with chronic hepatitis B, cirrhosis and hepatocellular carcinoma and represents the best marker of HBV-related clinical progression as compared with several other cytokines. In this study, we found that IL-6 was able to effectively suppress hepatitis B virus (HBV) replication and prevent the accumulation of HBV covalently closed circular DNA (cccDNA) in a human hepatoma cell line. We also demonstrated that the suppression of HBV replication by IL-6 requires concurrently a moderate reduction of viral transcripts/core proteins and a marked decrease in viral genome-containing nucleocapsids. Studies on the stability of existing viral capsids suggest that the IL-6 effect on the reduction of genome-containing nucleocapsids is mediated through the prevention of the formation of genome-containing nucleocapsids, which is similar to the effect of interferons. However, IFN-α/β and IFN-γ did not participate in the IL-6-induced suppression of HBV replication. Taken together, our results will provide important information to better understand the role of IL-6 in the course of HBV infection.

Cytokines associated with bronchopulmonary dysplasia or death in extremely low birth weight infants

OBJECTIVE

The goal was to develop multivariate logistic regression models for the outcome of bronchopulmonary dysplasia and/or death at postmenstrual age of 36 weeks by using clinical and cytokine data from the first 28 days.

METHODS

For 1067 extremely low birth weight infants in the Neonatal Research Network of the National Institute of Child Health and Human Development, levels of 25 cytokines were measured in blood collected within 4 hours after birth and on days 3, 7, 14, and 21. Stepwise regression analyses using peak levels of the 25 cytokines and 15 clinical variables identified variables associated with bronchopulmonary dysplasia/death. Multivariate logistic regression analysis was performed for bronchopulmonary dysplasia/death by using variables selected through stepwise regression. Similar analyses were performed by using average cytokine values from days 0 to 21, days 0 to 3, and days 14 to 21.

RESULTS

Of 1062 infants with available data, 606 infants developed bronchopulmonary dysplasia or died. On the basis of results from all models combined, bronchopulmonary dysplasia/death was associated with higher concentrations of interleukin 1beta, 6, 8, and 10 and interferon gamma and lower concentrations of interleukin 17, regulated on activation, normal T cell expressed and secreted, and tumor necrosis factor beta. Compared with models with only clinical variables, the addition of cytokine data improved predictive ability by a statistically significant but clinically modest magnitude.

CONCLUSIONS

The overall cytokine pattern suggests that bronchopulmonary dysplasia/death may be associated with impairment in the transition from the innate immune response mediated by neutrophils to the adaptive immune response mediated by T lymphocytes.

Interleukin-6 released from fibroblasts is essential for up-regulation of matrix metalloproteinase-1 expression by U937 macrophages in coculture: cross-talking between fibroblasts and U937 macrophages exposed to high glucose

Matrix metalloproteinases (MMPs) play a key role in periodontal disease. Although it is known that macrophages and fibroblasts are co-localized and express MMPs in the diseased periodontal tissue, the effect of interaction between these two cell types on MMP expression has not been well elucidated. Furthermore although it is known that diabetes is associated with accelerated periodontal tissue destruction, it remains unknown whether hyperglycemia, a major metabolic abnormality in diabetes, regulates MMP expression by affecting the cross-talking between fibroblasts and macrophages. In this study, human gingival fibroblasts and U937 macrophages were cocultured in a two-compartment transwell culture system, and the cells were treated with normal or high glucose. We found that coculture of fibroblasts and U937 macrophages led to an augmentation of MMP-1 expression by U937 macrophages, and high glucose further enhanced this augmentation. Similar observations were also made in the coculture of fibroblasts and human primary monocytes. We also found that interleukin 6 (IL-6) released by fibroblasts was essential for the augmentation of MMP-1 expression by U937 macrophages. Furthermore our results showed that high glucose, IL-6, and lipopolysaccharide had a synergistic effect on MMP-1 expression. Finally our study indicated that MAPK pathways and activator protein-1 transcription factor were involved in the coculture- and high glucose-augmented MMP-1 expression. In conclusion, this study demonstrates that IL-6 derived from fibroblasts is essential for MMP-1 up-regulation by cross-talking between fibroblasts and U937 macrophages exposed to high glucose, revealing an IL-6-dependent mechanism in MMP-1 up-regulation.

Impact of interleukin-6 on hypoxia-induced pulmonary hypertension and lung inflammation in mice

Background

Inflammation may contribute to the pathogenesis of various forms of pulmonary hypertension (PH). Recent studies in patients with idiopathic PH or PH associated with underlying diseases suggest a role for interleukin-6 (IL-6).

Methods

To determine whether endogenous IL-6 contributes to mediate hypoxic PH and lung inflammation, we studied IL-6-deficient (IL-6^-/-) and wild-type (IL-6^+/+) mice exposed to hypoxia for 2 weeks.

Results

Right ventricular systolic pressure, right ventricle hypertrophy, and the number and media thickness of muscular pulmonary vessels were decreased in IL-6^-/- mice compared to wild-type controls after 2 weeks' hypoxia, although the pressure response to acute hypoxia was similar in IL-6^+/+ and IL-6^-/- mice. Hypoxia exposure of IL-6^+/+ mice led to marked increases in IL-6 mRNA and protein levels within the first week, with positive IL-6 immunostaining in the pulmonary vessel walls. Lung IL-6 receptor and gp 130 (the IL-6 signal transducer) mRNA levels increased after 1 and 2 weeks' hypoxia. In vitro studies of cultured human pulmonary-artery smooth-muscle-cells (PA-SMCs) and microvascular endothelial cells revealed prominent synthesis of IL-6 by PA-SMCs, with further stimulation by hypoxia. IL-6 also markedly stimulated PA-SMC migration without affecting proliferation. Hypoxic IL-6^-/- mice showed less inflammatory cell recruitment in the lungs, compared to hypoxic wild-type mice, as assessed by lung protein levels and immunostaining for the specific macrophage marker F4/80, with no difference in lung expression of adhesion molecules or cytokines.

Conclusion

These data suggest that IL-6 may be actively involved in hypoxia-induced lung inflammation and pulmonary vascular remodeling in mice.

The effects of IL-6 on CD4 T cell responses

Cytokines have long been known to profoundly influence the adaptive immune response by determining CD4 T cell differentiation. Although IL-6 has been initially characterized as a B cell growth factor and inducer of antibody production research from our lab and others has revealed over the last years that IL-6 also plays a significant role in CD4 T cell differentiation. This review highlights the variety of ways in which IL-6 affects CD4 effector functions and how this may contribute to different types of diseases.