Signaling mechanisms through gp130: a model of the cytokine system

ZFAT is a critical molecule for cell survival in mouse embryonic fibroblasts

ZFAT was originally identified as an immune-related transcriptional regulator containing 18 C2H2-type zinc-finger domains and one AT-hook. ZFAT is highly conserved among species and functions as an anti-apoptotic molecule in the lymphoblastic leukemia cell line, MOLT-4. We recently demonstrated that ZFAT is an essential molecule for hematopoietic differentiation in blood islands through the direct regulation of particular transcriptional factors, including Tal1, for endothelial cell assembly, and for the branch point formation of capillary-like structures. However, the molecular mechanisms underlying the anti-apoptotic function of ZFAT remain unknown. Here, we report that ZFAT knockdown by small interfering RNA induced apoptosis in mouse embryonic fibroblasts (MEFs). This response had been similarly observed for MOLT-4 cells. To explore the molecular mechanisms for ZFAT in anti-apoptotic function in both MEFs and MOLT-4 cells, microarray expression analysis and quantitative RT-PCR were done. Of interest was that Bcl-2 and Il6st were identified as commonly down-regulated genes by the depletion of ZFAT for both MEFs and MOLT-4 cells. These results suggest that ZFAT is a critical molecule for cell survival in MEFs and MOLT-4 cells at least in part through the regulation of the apoptosis involved in the BCL-2- and IL6st-mediated pathways. Further elucidation of the molecular functions for ZFAT might shed light on the cellular programs in the mesoderm-derived cells.

The use of leukemia inhibitory factor immobilized on virus-derived polyhedra to support the proliferation of mouse embryonic and induced pluripotent stem cells

Human leukemia inhibitory factor (LIF) was immobilized into insect virus-derived microcrystals (polyhedra) to generate LIF polyhedra (LIF-PH) that can slowly release LIF into embryonic stem (ES) cell culture media and thus maintain ES cells in an undifferentiated state. Assays of the biological activities of LIF-PH indicated that a single addition of LIF-PH to the ES cell culture medium can support the proliferation of mouse ES and induced pluripotent stem (iPS) cells continuously for 14 days, and suggest that LIF-PH can be successfully used in the place of a periodic addition of recombinant LIF to the media every 2-3 days. The release of LIF protein from LIF-PH was determined by enzyme-linked immunosorbent assay (ELISA). Maintenance of undifferentiated state of mouse ES and iPS cells cultured with LIF-PH was determined by the detection of pluripotency-related biomarkers Oct3/4 and stage-specific embryonic antigen-1 (SSEA-1) through immunostaining and measurement of alkaline phosphatase activity. In this paper, we propose a closed culture system for mass production of ES and iPS cells that utilize a slow-releasing agent of LIF.

Functional involvement of Daxx in gp130-mediated cell growth and survival in BaF3 cells

Death domain-associated protein (Daxx) is a multifunctional protein that modulates both cell death and transcription. Several recent studies have indicated that Daxx is a mediator of lymphocyte death and/or growth suppression, although the detailed mechanism is unclear. Previously, we reported that Daxx suppresses IL-6 family cytokine-induced gene expression by interacting with STAT3. STAT3 is important for the growth and survival of lymphocytes; therefore, we here examined the role of Daxx in the gp130/STAT3-dependent cell growth/survival signals. We found that Daxx suppresses the gp130/STAT3-dependent cell growth and that Daxx endogenously interacts with STAT3 and inhibits the DNA-binding activity of STAT3. Moreover, small-interfering RNA-mediated knockdown of Daxx enhanced the expression of STAT3-target genes and accelerated the STAT3-mediated cell cycle progression. In addition, knockdown of Daxx-attenuated lactate dehydrogenase leakage from cells, indicating that Daxx positively regulates cell death during gp130/STAT3-mediated cell proliferation. Notably, Daxx specifically suppressed the levels of Bcl2 mRNA and protein, even in cytokine-unstimulated cells, indicating that Daxx regulates Bcl2 expression independently of activated STAT3. These results suggest that Daxx suppresses gp130-mediated cell growth and survival by two independent mechanisms: inhibition of STAT3-induced transcription and down-regulation of Bcl2 expression.

Eye transformer is a negative regulator of Drosophila JAK/STAT signaling

JAK/STAT signaling pathway is evolutionarily conserved and tightly regulated. We carried out a reporter-based genome-wide RNAi in vitro screen to identify genes that regulate Drosophila JAK/STAT pathway and found 5 novel regulators. Of these, CG14225 is a negative regulator structurally related to the Drosophila JAK/STAT pathway receptor Domeless, especially in the extracellular domain, and to the mammalian IL-6 receptor and the signal transducer gp130. CG14225 coimmunoprecipitates with Domeless and its associated kinase hopscotch in S2 cells. CG14225 RNAi caused hyperphosphorylation of the transcription factor Stat92E in S2 cells on stimulation with the Drosophila JAK/STAT pathway ligand unpaired. CG14225 RNAi in vivo hyperactivated JAK/STAT target genes on septic injury and enhanced unpaired-induced eye overgrowth, and was thus named the eye transformer (ET). In the gastrointestinal infection model, where JAK/STAT signaling is important for stem cell renewal, CG14225/ET RNAi was protective in vivo. In conclusion, we have identified ET as a novel negative regulator of the Drosophila JAK/STAT pathway both in vitro and in vivo, and it functions in regulating Stat92E phosphorylation.

Autocrine production of interleukin-6 confers cisplatin and paclitaxel resistance in ovarian cancer cells

It has been shown that IL-6 is elevated in the serum and ascites of ovarian cancer patients, and increased IL-6 concentration correlates with poor prognosis and chemoresistance. However, the role of IL-6 expression in the acquisition of the chemoresistance phenotype and the underlining mechanisms of drug resistance in ovarian cancer cells remain unclear. Here we demonstrate that both exogenous (a relatively short period of treatment with recombination IL-6) and endogenous IL-6 (by transfecting with plasmid encoding for sense IL-6) induce cisplatin and paclitaxel resistance in non-IL-6-expressing A2780 cells, while deleting of endogenous IL-6 expression in IL-6-overexpressing SKOV3 cells (by transfecting with plasmid encoding for antisense IL-6) promotes the sensitivity of these cells to anticancer drugs. IL-6-mediated resistance of ovarian cancer cells exhibits decreased proteolytic activation of caspase-3. Meanwhile, the further study demonstrates that the chemoresistance caused by IL-6 is associated with increased expression of both multidrug resistance-related genes (MDR1 and GSTpi) and apoptosis inhibitory proteins (Bcl-2, Bcl-xL and XIAP), as well as activation of Ras/MEK/ERK and PI3K/Akt signaling. Therefore, modulation of IL-6 expression or its related signaling pathway may be a promising strategy of treatment for drug-resistant ovarian cancer.

Human herpesvirus 8-encoded cytokines

Human herpesvirus (HHV)-8, also called Kaposi's sarcoma-associated herpesvirus, was discovered in 1994 and was rapidly sequenced, revealing several unique and surprising features of its genetic makeup. Among these discoveries was the identification of the first viral homolog of IL-6 and three CC/beta-chemokine ligands (viral CCL-1, -2 and -3), not previously found in gamma-herpesviruses. Viral IL-6 was immediately recognized as a potential contributor to HHV-8 pathogenesis, specifically endothelial-derived Kaposi's sarcoma and the B-cell malignancy multicentric Castleman's disease with which IL-6, a proangiogenic and B-cell growth factor, had previously been implicated. The roles of the viral chemokines were speculated to involve immune evasion; however, like viral IL-6, the viral chemokines have the potential to contribute to pathogenesis through their shared angiogenic activities, known to be important for Kaposi's sarcoma and HHV-8-associated primary effusion lymphoma, and also via direct prosurvival activities. This article will discuss the molecular properties, activities and functions of viral IL-6 and the viral CCLs, proteins that could provide appropriate targets for antiviral and therapeutic strategies.

gp130-mediated pathway and heart failure

Binding of ligands to gp130 activates at least three different downstream signaling pathways: the signal transducer and activator of transcription (STAT), the Src-homology tyrosine phosphatase 2-ras-MAPK and the PI3K/Akt pathways. Cardiac-specific disruption of gp130 was shown to result in heart failure in response to mechano-stress accompanied by an increase in apoptosis of cardiac myocytes. Inactivation of STAT3 resulting from the loss of gp130 may be a key event in the transition from cardiac hypertrophy to heart failure. Proper vascular growth would be essential for normal cardiac development and the remodeling process. In addition to various factors, such as bcl-xL, inducible nitric oxide synthase and reactive oxygen species-scavenging proteins, VEGF has also been identified as a target gene of STAT3 and together can promote cardiac myocyte survival by preventing apoptosis and restoration of energy deprivation. In this regard, the gp130-receptor system and its main downstream mediator, STAT3, play a key role in the prevention of heart failure. In this review, current knowledge of the IL-6 family of cytokines relating to human cardiac disease is summarized, in addition to the potential role of gp130-mediated signaling systems in various models of experimental heart failure.

Cytokines in idiopathic inflammatory myopathies

Recent findings suggest cytokines as important key molecules in the pathogenic mechanisms of idiopathic inflammatory myopathies, myositis. In this review, we focus on cytokines with a potential role in disease mechanisms in myositis and present some general information on individual cytokines and an updated summary from the literature concerning cytokines in these disorders. The idiopathic inflammatory myopathies is a heterogeneous group of disorders clinically characterized by symmetric proximal muscle weakness and by certain defined histolopathological findings, including inflammatory infiltrates in muscle tissue. Other prominent findings in the target tissue of these patients are defined molecular changes of blood vessels and muscle fibers, including reformation to high endothelial venule (HEV)-like blood vessels and intensive MHC class I expression in muscle fibers. The predominant clinical symptoms of muscle weakness and decreased muscle endurance are shared by all subsets of inflammatory myopathies and indicate that some pathogenic mechanisms related to muscle function may be shared by the different disease groups. Studies on cytokine gene, RNA and protein expression in muscle tissue from patients with various forms of the disease also indicate similar profiles, despite different phenotypes of the inflammatory cells present in muscle tissue from the different subsets of myositis. There is a pronounced expression of various cytokines in muscle tissue, among which the proinflammatory cytokines TNF-alpha and IL-1 are most widely explored in the inflammatory myopathies, which has made them into potential therapeutic targets. The use of targeted cytokine therapy has been successful in several other chronic inflammatory diseases and although the exact role of cytokines in chronic idiopathic inflammatory myopathies remains to be delineated their potential role as targets for new therapies in this disorder will be discussed in this review.

Foxa1 and Foxa2 regulate bile duct development in mice

The forkhead box proteins A1 and A2 (Foxa1 and Foxa2) are transcription factors with critical roles in establishing the developmental competence of the foregut endoderm and in initiating liver specification. Using conditional gene ablation during a later phase of liver development, we show here that deletion of both Foxa1 and Foxa2 (Foxa1/2) in the embryonic liver caused hyperplasia of the biliary tree. Abnormal bile duct formation in Foxa1/2-deficient liver was due, at least in part, to activation of IL-6 expression, a proliferative signal for cholangiocytes. The glucocorticoid receptor is a negative regulator of IL-6 transcription; in the absence of Foxa1/2, the glucocorticoid receptor failed to bind to the IL-6 promoter, causing enhanced IL-6 expression. Thus, after liver specification, Foxa1/2 are required for normal bile duct development through prevention of excess cholangiocyte proliferation. Our data suggest that Foxa1/2 function as terminators of bile duct expansion in the adult liver through inhibition of IL-6 expression.

Raised expression of cytokine receptor gp130 subunit on peripheral lymphocytes of patients with active lupus. A useful tool for monitoring the disease activity?

The glycoprotein gp130 is a signal traducing subunit with a membrane domain of the IL-6 receptor. In addition, gp130 is shared among the receptors for IL-6 superfamily, and it is critically involved in generating signal transduction through these receptors. The aim of the study is to evaluate the expression of the IL-6 superfamily receptor molecule gp130 on TCD4(+) and B cells in patients with systemic lupus erythematosus (SLE). Surface expression of gp130 on TCD4(+) and B lymphocytes was higher in patients with SLE than in healthy controls (2.79 vs 0.36% and 8.36 vs 0.37%, respectively). Patients with active lupus had higher expression of gp130 (relapsed 15.1%, new onset 26.6%) than stable patients (2.83%), in B-cell subset, but not in TCD4 lymphocytes. An important reduction in the gp130 expression on B lymphocytes was observed when the activity of the disease had disappeared after readjusting its immunosuppressive treatment (20.8-3.8%). In addition, there was significant correlation between the activity of the disease, measured like systemic lupus erythematosus disease activity index score, and surface expression of gp130 in lymphocytes B (r(s) = 0.5880, P = 0.0002). According with our results and roc curve analysis, a cut-off in 6.7% of B cells with gp130 expression were defined, who discriminates active/stable SLE with a sensitivity of 0.93 and a specificity of 0.75. In conclusion, there is an altered expression of gp130 in the patients with SLE. The disease activity as well as immunotherapy seems to influence the pattern of expression of gp130 on B-cell subsets in patients with SLE.

IL-6 cytoprotection in hyperoxic acute lung injury occurs via PI3K/Akt-mediated Bax phosphorylation

IL-6 overexpression protects mice from hyperoxic acute lung injury in vivo, and treatment with IL-6 protects cells from oxidant-mediated death in vitro. The mechanisms of protection, however, are not clear. We characterized the expression, localization, and regulation of Bax, a proapoptotic member of the Bcl-2 family, in wild-type (WT) and IL-6 lung-specific transgenic (Tg(+)) mice exposed to 100% O(2) and in human umbilical vein endothelial cells (HUVEC) treated with H(2)O(2) and IL-6. In control HUVEC treated with H(2)O(2) or in WT mice exposed to 100% O(2), a marked induction of Bax translocation and dimerization was associated with increased JNK and p38 kinase activity. In contrast, specific JNK or p38 kinase inhibitors or treatment with IL-6 inhibited Bax mitochondrial translocation and apoptosis of HUVEC. IL-6 Tg(+) mice exposed to 100% O(2) exhibited enhanced phosphatidylinositol 3-kinase (PI3K)/Akt kinase and increased serine phosphorylation of Bax at Ser(184) compared with WT mice. The PI3K-specific inhibitor LY-2940002 blocked this IL-6-induced Bax phosphorylation and promoted cell death. Furthermore, IL-6 potently blocked hyperoxia- or oxidant-induced Bax insertion into mitochondrial membranes. Thus IL-6 functions in a cytoprotective manner, in part, by suppressing Bax translocation and dimerization through PI3K/Akt-mediated Bax phosphorylation.

IL-6-induced activation of MYC is responsible for the down-regulation of CD33 expression in CD33+ myeloma cells

Human myeloma cells from about 10% of cases with multiple myeloma expressed CD33 and had monocytoid morphology with convoluted nuclei, and all these patients had no increase in serum CRP values. In CD33(+) myeloma cells as well as myeloma cell lines, CD33 expression levels were correlated with the increased expression levels of CEBPA (C/EBPalpha). This correlation was confirmed by the finding that transfection with the CEBPA gene induced CD33 expression in a CD33(-) myeloma cell line. As suggested by the lack of an increase in serum CRP values in CD33(+) myelomas, IL-6 down-regulated the expression of CD33 in CD33(+) myeloma cell lines along with the down-regulation of CEBPA gene expression. Cucurbitacin I (STAT3 inhibitor), but not U0126 (MAPK inhibitor), could abolish the effect of IL-6. Furthermore, IL-6 up-regulated the expression of MYC via STAT3 phosphorylation and MYC bound to the promoter region of the CEBPA gene followed by the down-regulation of CEBPA expression. It was confirmed that introduction of shRNA for MYC into a CD33(+) myeloma cell line blocked the IL-6-induced down-regulation of CD33 and CEBPA expression. Therefore, these results indicate that IL-6 can reverse the expression level of CD33 by up-regulating MYC followed by the down-regulation of CEBPA expression.

Three LIF-dependent signatures and gene clusters with atypical expression profiles, identified by transcriptome studies in mouse ES cells and early derivatives

Background

Mouse embryonic stem (ES) cells remain pluripotent in vitro when grown in the presence of the cytokine Leukaemia Inhibitory Factor (LIF). Identification of LIF targets and of genes regulating the transition between pluripotent and early differentiated cells is a critical step for understanding the control of ES cell pluripotency.

Results

By gene profiling studies carried out with mRNAs from ES cells and their early derivatives treated or not with LIF, we have identified i) LIF-dependent genes, highly expressed in pluripotent cells, whose expression level decreases sharply upon LIF withdrawal [Pluri genes], ii) LIF induced genes [Lifind genes] whose expression is differentially regulated depending upon cell context and iii) genes specific to the reversible or irreversible committed states. In addition, by hierarchical gene clustering, we have identified, among eight independent gene clusters, two atypical groups of genes, whose expression level was highly modulated in committed cells only. Computer based analyses led to the characterization of different sub-types of Pluri and Lifind genes, and revealed their differential modulation by Oct4 or Nanog master genes. Individual knock down of a selection of Pluri and Lifind genes leads to weak changes in the expression of early differentiation markers, in cell growth conditions in which these master genes are still expressed.

Conclusion

We have identified different sets of LIF-regulated genes depending upon the cell state (reversible or irreversible commitment), which allowed us to present a novel global view of LIF responses. We are also reporting on the identification of genes whose expression is strictly regulated during the commitment step. Furthermore, our studies identify sub-networks of genes with a restricted expression in pluripotent ES cells, whose down regulation occurs while the master knot (composed of OCT4, SOX2 and NANOG) is still expressed and which might be down-regulated together for driving cells towards differentiation.

Tocilizumab: the first interleukin-6-receptor inhibitor

PURPOSE

The pharmacology, pharmacokinetics, clinical efficacy, safety, and role of tocilizumab in rheumatoid arthritis (RA) are reviewed.

SUMMARY

Tocilizumab is a novel monoclonal antibody that competitively inhibits the binding of interleukin-6 (IL-6) to its receptor (IL-6R). Inhibiting the entire receptor complex prevents IL-6 signal transduction to inflammatory mediators that summon B and T cells. Tocilizumab has a nonlinear pharmacokinetic profile. The hypothesis that targeting and inhibiting IL-6R with tocilizumab can result in significant improvement of the signs and symptoms of RA appears to have been substantiated in one Phase III and two Phase II clinical trials, which have demonstrated a marked reduction in disease activity and the acute-phase response. The results of these studies indicate that tocilizumab treatment, both as a combination with methotrexate and as monotherapy, has a safety profile consistent with that of other biological and immunosuppressive therapies. In general, tocilizumab as monotherapy and in combination with methotrexate appears to be well tolerated. Adverse events were not dose dependent and were of similar frequency in all groups. Tocilizumab appears to provide an additional option for those patients who do not respond sufficiently to methotrexate. Since IL-6R inhibition has a distinct mechanism of action, some patients who do not respond to antitumor necrosis factor agents or who have a partial response may respond to tocilizumab.

CONCLUSION

Tocilizumab, a novel IL-6R inhibitor, may be beneficial for the treatment of RA in patients who do not respond to methotrexate or disease-modifying antirheumatic drugs. A large clinical trial is needed to confirm tocilizumab's clinical efficacy and safety.

Apoptosis induction and attenuation of inflammatory gene expression in murine macrophages via multitherapeutic nanomembranes

The realization of optimized therapeutic delivery is impaired by the challenge of localized drug activity and by the dangers of systemic cytotoxicity which often contribute to patient treatment complications. Here we demonstrate the block copolymer-mediated deposition and release of multiple therapeutics which include an LXRα/β agonist 3-((4-methoxyphenyl)amino)-4-phenyl-1-(phenylmethyl)-1H-pyrrole-2,5-dione (LXRa) and doxorubicin hydrochloride (Dox) at the air-water interface via Langmuir-Blodgett deposition, as well as copolymer-mediated potent drug elution toward the Raw 264.7 murine macrophage cell line. The resultant copolymer-therapeutic hybrid serves as a localized platform that can be functionalized with virtually any drug due to the integrated hydrophilic and hydrophobic components of the polymer structure. In addition, the sequestering function of the copolymer to anchor the drugs to implant surfaces can enhance delivery specificity when compared to systemic drug administration. Confirmation of drug functionality was confirmed via suppression of the interleukin 6 (Il-6) and tumor necrosis factor alpha (TNFα) inflammatory cytokines (LXRa), as well as DNA fragmentation analysis (Dox). Furthermore, the fragmentation assays and gene expression analysis demonstrated the innate biocompatibility of the copolymeric material at the gene expression level via the confirmed absence of material-induced apoptosis and a lack of inflammatory gene expression. This modality enables layer-by-layer control of agonist and chemotherapeutic functionalization at the nanoscale for the localization of drug dosage, while simultaneously utilizing the copolymer platform as an anchoring mechanism for drug sequestering, all with an innate material thickness of 4 nm per layer, which is orders of magnitude thinner than existing commercial technologies. Furthermore, these studies comprehensively confirmed the potential translational applicability of copolymeric nanomaterials as localized multitherapeutic thin film platforms.

IL-6 Promotes compensatory liver regeneration in cirrhotic rat after partial hepatectomy

Major hepatic resection in cirrhotic patients is associated with impaired liver regeneration and failure, leading to high peri-operative mortality. In this work, the causes of defective regeneration in cirrhotic liver and the utility of IL-6 treatment were investigated in an experimental model combining cirrhosis and partial hepatectomy in the rat. Relative to normal controls, decompensated cirrhotic animals showed decreased survival, while compensated cirrhotic animals showed similar survival but reduced hepatic DNA synthesis and newly regenerated liver mass amount. Defective liver regeneration was associated with a decrease in STAT3 and NF-kB activation, consistent with an increased accumulation of their respective inhibitors PIAS3 and IkBalpha, and with a decreased induction of Bcl-xL. Treatment with recombinant IL-6 enhanced survival of decompensated cirrhotic animals, while it did not affect survival of compensated cirrhotic animals but sustained liver regeneration, by restoring STAT3 and NF-kB activation and Bcl-xL induction to the levels found in normal controls. The pro-growth effects exerted by IL-6 treatment in cirrhotic liver were attained also at low, pharmacologically acceptable doses. In conclusion, our results suggest that IL-6 treatment may be therapeutic in major resection of cirrhotic liver.

Steel factor coordinately regulates the molecular signature and biologic function of hematopoietic stem cells

Hematopoietic stem cells (HSCs) regenerated in vivo display sustained differences in their self-renewal and differentiation activities. Variations in Steel factor (SF) signaling are known to affect these functions in vitro, but the cellular and molecular mechanisms involved are not understood. To address these issues, we evaluated highly purified HSCs maintained in single-cell serum-free cultures containing 20 ng/mL IL-11 plus 1, 10, or 300 ng/mL SF. Under all conditions, more than 99% of the cells traversed a first cell cycle with similar kinetics. After 8 hours in the 10 or 300 ng/mL SF conditions, the frequency of HSCs remained unchanged. However, in the next 8 hours (ie, 6 hours before any cell divided), HSC integrity was sustained only in the 300 ng/mL SF cultures. The cells in these cultures also contained significantly higher levels of Bmi1, Lnk, and Ezh2 transcripts but not of several other regulators. Assessment of 21 first division progeny pairs further showed that only those generated in 300 ng/mL SF cultures contained HSCs and pairs of progeny with similar differentiation programs were not observed. Thus, SF signaling intensity can directly and coordinately alter the transcription factor profile and long-term repopulating ability of quiescent HSCs before their first division.

The IL-6 family of cytokines modulates STAT3 activation by desumoylation of PML through SENP1 induction

Post-translational modification by small ubiquitin-like modifier (SUMO) plays an important role in the regulation of different signaling pathways and is involved in the formation of promyelocytic leukemia (PML) protein nuclear bodies following sumoylation of PML. In the present study, we found that IL-6 induces desumoylation of PML and dissociation between PML and SUMO1 in hepatoma cells. We also found that IL-6 induces mRNA expression of SENP1, a member of the SUMO-specific protease family. Furthermore, wild-type SENP1 but not an inactive SENP1 mutant restored the PML-mediated suppression of STAT3 activation. These results indicate that the IL-6 family of cytokines modulates STAT3 activation by desumoylation and inactivation PML through SENP1 induction.

Role of gp130-mediated signalling pathways in the heart and its impact on potential therapeutic aspects

IL-6-type cytokines bind to plasma membrane receptor complexes containing the common signal transducing receptor chain gp130 that is ubiquitously expressed in most tissues including the heart. The two major signalling cascades activated by the gp130 receptor, SHP2/ERK and STAT pathways, have been demonstrated to play important roles in cardiac development, hypertrophy, protection and remodelling in response to physiological and pathophysiological stimuli. Experimental data, both in vivo and in vitro, imply beneficial effects of gp130 signalling on cardiomyocytes in terms of growth and survival. In contrast, it has been reported that elevated serum levels of IL-6 cytokines and gp130 proteins are strong prognostic markers for morbidity and mortality in patients with heart failure or after myocardial infarction. Moreover, it has been shown that the local gp130 receptor system is altered in failing human hearts. In the present review, we summarize the basic principles of gp130 signalling, which requires simultaneous activation of STAT and ERK pathways under the tight control of positive and negative intracellular signalling modulators to provide a balanced biological outcome. Furthermore, we highlight the key role of the gp130 receptor and its major downstream effectors in the heart in terms of development and regeneration and in response to various physiological and pathophysiological stress situations. Finally, we comment on tissue-specific diversity and challenges in targeted pharmacological interference with components of the gp130 receptor system.

Protein-mediated assembly of nanodiamond hydrogels into a biocompatible and biofunctional multilayer nanofilm

Aqueous dispersible detonation nanodiamonds (NDs) with a diameter of 2-8 nm were assembled into a closely packed ND multilayer nanofilm with positively charged poly-L-lysine via the layer-by-layer deposition technique. The innate biocompatibility of the NDs in both free-floating and thin-film forms was confirmed via cellular gene expression examination by real-time polymerase chain reaction as well as MTT and DNA fragmentation assays. The highly biologically amenable ND nanofilm was successfully integrated with therapeutic molecules, and the functionality of the composite drug-ND material was assessed via interrogation of the suppression of inflammatory cytokine release. Knockdown of lipopolysaccharide-mediated inflammation was observed through the potent attenuation of tumor necrosis factor-alpha, interleukin-6, and inducible nitric oxide synthase levels following ND nanofilm interfacing with RAW 264.7 murine macrophages. Furthermore, basal cytokine secretion levels were assessed to examine innate material biocompability, revealing unchanged cellular inflammatory responses which strongly supported the relevance of the NDs as effective treatment platforms for nanoscale medicine. In addition to the easy preparation, robustness, and fine controllability of the film structures, these hybrid materials possess enormous potential for biomedical applications such as localized drug delivery and anti-inflammatory implant coatings and devices, as demonstrated in vitro in this work.

Cytokine-mimetic properties of some Philippine food and medicinal plants

This study evaluated Philippine indigenous plants for cytokine-mimetic properties and partially characterized candidate mimetics for their stability as well as their sensitivity to variations in temperature and pH. Forty-five plant extract preparations were tested for their ability to stimulate proliferation of mouse spleen cells and bone marrow cells. Temperature and pH effects were determined by subjecting the extracts to different temperature and pH levels and measuring their residual proliferative activities. Results revealed that 24 and 14 extracts were able to stimulate proliferation of bone marrow cells and spleen cells, respectively. Extracts from yam (Dioscorea alata L.) (Dioscoreaceae) roots and leaves, taro (Colocasia esculenta L.) (Araceae) roots, and buyo (Piper betle L.) (Piperaceae) leaf were among the extracts that strongly stimulated proliferation of both bone marrow cells and splenocytes, significantly increasing cell concentrations. Heating the extracts beyond 40 degrees C markedly reduced their proliferative ability, while a pH level below 4.0 and above 8.0 also significantly decreased the extracts' activity. Three protein-mimetics with sizes of 26 kDa, 35 kDa, and 50 kDa were isolated from buyo leaf, yam root, and taro root extracts, respectively. All three molecules are biologically active and stimulate a dose-dependent proliferative response.

Active nanodiamond hydrogels for chemotherapeutic delivery

Nanodiamond materials can serve as highly versatile platforms for the controlled functionalization and delivery of a wide spectrum of therapeutic elements. In this work, doxorubicin hydrochloride (DOX), an apoptosis-inducing drug widely used in chemotherapy, was successfully applied toward the functionalization of nanodiamond materials (NDs, 2-8 nm) and introduced toward murine macrophages as well as human colorectal carcinoma cells with preserved efficacy. The adsorption of DOX onto the NDs and its reversible release were achieved by regulating Cl- ion concentration, and the NDs were found to be able to efficiently ferry the drug inside living cells. Comprehensive bioassays were performed to assess and confirm the innate biocompatibility of the NDs, via real-time quantitative polymerase chain reaction (RT-PCR), and electrophoretic DNA fragmentation as well as MTT analysis confirmed the functional apoptosis-inducing mechanisms driven by the DOX-functionalized NDs. We extended the applicability of the DOX-ND composites toward a translational context, where MTT assays were performed on the HT-29 colon cancer cell line to assess DOX-ND induced cell death and ND-mediated chemotherapeutic sequestering for potential slow/sustained released capabilities. These and other medically relevant capabilities enabled by the NDs forge its strong potential as a therapeutically significant nanomaterial.

Association of depressed cardiac gp130-mediated antiapoptotic pathways with stimulated cardiomyocyte apoptosis in hypertensive patients with heart failure

OBJECTIVE

To investigate whether the glycoprotein (gp130)-mediated survival pathway, which protects cardiomyocytes from apoptosis, is depressed in left ventricular hypertrophy hypertensive patients with chronic heart failure.

METHODS

Transvenous endomyocardial biopsies were obtained in 52 hypertensive patients with left ventricular hypertrophy: 28 without heart failure and 24 with heart failure. gp130 and gp130-dependent antiapoptotic pathways p42/44 mitogen-activated protein kinase (MAPK) and phosphatidylinositol-3 kinase (PI3K)/protein kinase B (Akt) as well as gp130 agonist cardiotrophin-1 were analyzed by reverse transcriptase-polymerase chain reaction and western blot. Apoptosis was assessed by DNA end-labeling (TUNEL), caspase-3 immunostaining and caspase substrate poly(ADP-ribose) polymerase cleavage.

RESULTS

gp130 protein expression (P < 0.05) and p42/44 MAPK and PI3K/Akt activation (P < 0.01) were decreased in heart-failure hypertensive patients compared with nonheart-failure hypertensive individuals. No changes in gp130 mRNA expression were found between the two groups. Cardiotrophin-1 was increased (P < 0.05) at both the mRNA and protein levels in heart-failure hypertensive individuals compared with nonheart-failure hypertensive individuals. Cardiomyocyte apoptosis was increased (P < 0.01) in heart-failure hypertensive individuals compared with nonheart-failure hypertensive individuals. Inverse correlations (P < 0.01) occurred between cardiomyocyte apoptosis and p42/44 MAPK and PI3K/Akt activation in all hypertensive patients. Cardiotrophin-1 correlated inversely (r = -0.554, P < 0.05) with gp130 in all hypertensive individuals. In cultured HL-1 cardiomyocytes, cardiotrophin-1 decreased (P < 0.05) the gp130:phosphorylated gp130 (at Ser782) ratio and increased (P < 0.05) gp130ubiquitination.

CONCLUSIONS

An association exists between depression of the gp130 cytoprotective pathway and stimulation of cardiomyocyte apoptosis in hypertensive patients that develop heart failure. Whether the excess of cardiotrophin-1 induces ligand-induced receptor down-regulation in these patients requires further study.

SHP2-mediated signaling cascade through gp130 is essential for LIF-dependent I CaL, [Ca2+]i transient, and APD increase in cardiomyocytes

Leukemia inhibitory factor (LIF), a cardiac hypertrophic cytokine, increases L-type Ca(2+) current (I(CaL)) via ERK-dependent and PKA-independent phosphorylation of serine 1829 in the Cav(1.2) subunit. The signaling cascade through gp130 is involved in this augmentation. However, there are two major cascades downstream of gp130, i.e. JAK/STAT3 and SHP2/ERK. In this study, we attempted to clarify which of these two cascades plays a more important role. Knock-in mouse line, in which the SHP2 signal was disrupted (gp130(F759/F759) group), and wild-type mice (WT group) were used. A whole-cell patch clamp experiment was performed, and intracellular Ca(2+) concentration ([Ca(2+)](i) transient) was monitored. The I(CaL) density and [Ca(2+)](i) transient were measured from the untreated cells and the cells treated with LIF or IL-6 and soluble IL-6 receptor (IL-6+sIL-6r). Action potential duration (APD) was also recorded from the ventricle of each mouse, with or without LIF. Both LIF and IL-6+sIL-6r increased I(CaL) density significantly in WT (+27.0%, n=16 p<0.05, and +32.2%, n=15, p<0.05, respectively), but not in gp130(F759/F759) (+9.4%, n=16, NS, and -6.1%, n=13, NS, respectively). Administration of LIF and IL-6+sIL-6r increased [Ca(2+)](i) transient significantly in WT (+18.8%, n=13, p<0.05, and +32.0%, n=21, p<0.05, respectively), but not in gp130(F759/F759) (-3.8%, n=7, NS, and -6.4%, n=10, NS, respectively). LIF prolonged APD(80) significantly in WT (10.5+/-4.3%, n=12, p<0.05), but not in gp130(F759/F759) (-2.1+/-11.2%, n=7, NS). SHP2-mediated signaling cascade is essential for the LIF and IL-6+sIL-6r-dependent increase in I(CaL), [Ca(2+)](i) transient and APD.

Pathobiology of cigarette smoke-induced chronic obstructive pulmonary disease

Chronic obstructive pulmonary diseases (COPD), comprised of pulmonary emphysema, chronic bronchitis, and structural and inflammatory changes of small airways, is a leading cause of morbidity and mortality in the world. A better understanding of the pathobiology of COPD is critical for the developing of novel therapies, as the majority of patients with the disease have little therapeutic options at the present time. The pathobiology of COPD encompasses multiple injurious processes including inflammation (excessive or inappropriate innate and adaptive immunity), cellular apoptosis, altered cellular and molecular alveolar maintenance program, abnormal cell repair, extracellular matrix destruction (protease and anti-protease imbalance), and oxidative stress (oxidant and antioxidant imbalance). These processes are triggered by urban and rural air pollutants and active and/or passive cigarette smoke and modified by cellular senescence and infection. A series of receptor-mediated signal transduction pathways are activated by reactive oxygen species and tobacco components, resulting in impairment of a variety of cell signaling and cytokine networks, subsequently leading to chronic airway responses with mucus production, airway remodeling, and alveolar destruction. The authors provide an updated insight into the molecular and cellular pathobiology of COPD based on human and/or animal data.

IL-6 induces AGS gastric cancer cell invasion via activation of the c-Src/RhoA/ROCK signaling pathway

Interleukin-6 (IL-6) is a multifunctional cytokine that is associated with the disease status and outcomes of gastric cancer. Nonetheless, the underlying mechanism of how IL-6 promotes the spread of gastric cancer is still unclear. In this study, we used a modified Boyden chamber assay to test the invasion ability of different gastric cancer cell lines. Liposome-mediated transfection was used to introduce an IL-6 expression vector into AGS cells, and the transfectants were further examined for the expression of active RhoA and phosphorylated Src using a pull-down assay and coimmunoprecipitation/Western blot analysis. Furthermore, RhoA expression in gastric adenocarcinoma specimens was investigated immunohistochemically. We documented that IL-6 could promote AGS cell motility and invasiveness, and inhibition of RhoA expression by dominant negative RhoA, C3 transferase, or dominant negative Src expressing plasmids could effectively decrease the invasiveness of IL-6 transfectants. We also documented an interaction between active RhoA and phosphorylated-Src following IL-6 treatment. Gastric cancers displaying high expression of RhoA are highly correlated with aggressive lymph node metastasis, more advanced tumor stage, histologically diffuse type and poorer survival. In conclusion, IL-6 induces AGS gastric cancer cell invasion via activation of the c-Src/RhoA/ROCK signaling pathway and RhoA expression could be used as a prognostic factor in patients with gastric adenocarcinoma.

Survival pathways in hypertrophy and heart failure: the gp130-STAT3 axis

Circulating levels of interleukin (IL)-6 and related cytokines are elevated in patients with congestive heart failure and after myocardial infarction. Serum IL-6 concentrations are related to decreasing functional status of these patients and provide important prognostic information.Moreover, in the failing human heart, multiple components of the IL-6- glycoprotein (gp)130 receptor system are impaired, implicating an important role of this system in cardiac pathophysiology.Experimental studies have shown that the common receptor subunit of IL-6 cytokines is phosphorylated in response to pressure overload and myocardial infarction and that it subsequently activates at least three different downstream signaling pathways, the signal transducers and activators of transcription 1 and 3 (STAT1/3), the Src-homology tyrosine phosphatase 2 (SHP2)-Ras-ERK, and the PI3K-Akt system. Gp130 receptor mediated signaling promotes cardiomyocyte survival, induces hypertrophy, modulates cardiac extracellular matrix and cardiac function. In this regard, the gp130 receptor system and its main downstream mediator STAT3 play a key role in cardioprotection. This review summarizes the current knowledge of IL-6 cytokines, gp130 receptor and STAT3 signaling in the heart exposed to physiological (aging, pregnancy) and pathophysiological stress (ischemia, pressure overload, inflammation and cardiotoxic agents) with a special focus on the potential role of individual IL-6 cytokines.

Cardiac myocyte cell cycle control in development, disease, and regeneration

Cardiac myocytes rapidly proliferate during fetal life but exit the cell cycle soon after birth in mammals. Although the extent to which adult cardiac myocytes are capable of cell cycle reentry is controversial and species-specific differences may exist, it appears that for the vast majority of adult cardiac myocytes the predominant form of growth postnatally is an increase in cell size (hypertrophy) not number. Unfortunately, this limits the ability of the heart to restore function after any significant injury. Interest in novel regenerative therapies has led to the accumulation of much information on the mechanisms that regulate the rapid proliferation of cardiac myocytes in utero, their cell cycle exit in the perinatal period, and the permanent arrest (terminal differentiation) in adult myocytes. The recent identification of cardiac progenitor cells capable of giving rise to cardiac myocyte-like cells has challenged the dogma that the heart is a terminally differentiated organ and opened new prospects for cardiac regeneration. In this review, we summarize the current understanding of cardiomyocyte cell cycle control in normal development and disease. In addition, we also discuss the potential usefulness of cardiomyocyte self-renewal as well as feasibility of therapeutic manipulation of the cardiac myocyte cell cycle for cardiac regeneration.

Leukemia inhibitory factor-induced phosphorylation of STAP-2 on tyrosine-250 is involved in its STAT3-enhancing activity

Signal transducing adaptor protein-2 (STAP-2) is a recently identified adaptor protein that contains Pleckstrin and Src homology 2 (SH2)-like domains as well as a YXXQ motif in its C-terminal region. Our previous studies revealed that STAP-2 binds to signal transducer and activator of transcription 3 (STAT3) and STAT5, and regulates their signaling pathways. In the present study, we identified tyrosine-250 (Tyr250) in STAP-2 as a major site of phosphorylation by v-src and Jak2, using a phospho-specific antibody against STAP-2 phosphorylated at Tyr250. Mutational analyses revealed that Tyr250 was involved in the STAT3-enhancing activity of STAP-2. We further found that leukemia inhibitory factor (LIF) stimulated STAP-2 Tyr250 phosphorylation in 293T and Hep3B cells. Moreover, endogenous STAP-2 was phosphorylated at Tyr250 following LIF stimulation of murine M1 cell line. Taken together, our findings demonstrate that endogenous STAP-2 is phosphorylated at Tyr250 and that this phosphorylation is involved in its function.

Reversal of inflammation-associated dihydrodiol dehydrogenases (AKR1C1 and AKR1C2) overexpression and drug resistance in nonsmall cell lung cancer cells by wogonin and chrysin

Dihydrodiol dehydrogenase (DDH) is a member of the aldo-keto reductases superfamily (AKR1C1-AKR1C4), which plays central roles in the metabolism of steroid hormone, prostaglandin and xenobiotics. We have previously detected overexpression of DDH as an indicator of poor prognosis and chemoresistance in human non-small lung cancer (NSCLC). We also found DDH expression to be closely related to chronic inflammatory conditions. The aim of this study was to investigate the links between inflammation, DDH expression and drug resistance in NSCLC cells. We showed that pro-inflammatory mediators including interleukin-6 (IL-6) could induce AKR1C1/1C2 expression in NSCLC cells and increase cellular resistance to cisplatin and adriamycin. This effect was nullified by Safingol, a protein kinase C inhibitor. Moreover, the expression of AKR1C1/1C2 was inversely correlated to NBS1 and apoptosis-inducing factor (AIF). We also showed that IL-6-induced AKR1C1/1C2 expression and drug resistance were inhibited by wogonin and chrysin, which are major flavonoids in Scutellaria baicalensis, a widely used traditional Chinese and Japanese medicine. In conclusion, this study demonstrated novel links of pro-inflammatory signals, AKR1C1/1C2 expression and drug resistance in NSCLC. The protein kinase C pathway may play an important role in this process. Overexpression of AKR1C1/1C2 may serve as a marker of chemoresistance. Further studies are warranted to evaluate wogonin and chrysin as a potential adjuvant therapy for drug-resistant NSCLC, especially for those with AKR1C1/1C2 overexpression.

The Interleukin-6 inflammation pathway from cholesterol to aging--role of statins, bisphosphonates and plant polyphenols in aging and age-related diseases

We describe the inflammation pathway from Cholesterol to Aging. Interleukin 6 mediated inflammation is implicated in age-related disorders including Atherosclerosis, Peripheral Vascular Disease, Coronary Artery Disease, Osteoporosis, Type 2 Diabetes, Dementia and Alzheimer's disease and some forms of Arthritis and Cancer. Statins and Bisphosphonates inhibit Interleukin 6 mediated inflammation indirectly through regulation of endogenous cholesterol synthesis and isoprenoid depletion. Polyphenolic compounds found in plants, fruits and vegetables inhibit Interleukin 6 mediated inflammation by direct inhibition of the signal transduction pathway. Therapeutic targets for the control of all the above diseases should include inhibition of Interleukin-6 mediated inflammation.

Significance of autologous interleukin-6 production in the HA22T/VGH cell model of hepatocellular carcinoma

Cancer cells may often support their own growth, survival, and drug resistance by autocrine/paracrine loops based on the production of different factors; results from us and others have shown that similar interleukin-6 (IL-6)-related loops are operative in multiple myeloma and prostate or renal cancer. Because this aspect has not been investigated in detail for hepatocellular carcinoma (HCC), we have examined it in HA22T/VGH cells. These differ from other primary liver cancer cell lines (that is, HepG2, HuH-6, and HuH-7) in that enzyme-linked immunosorbent assay (ELISA) showed the HA22T/VGH cells to secrete remarkable amounts of IL-6 (16.8 ng/10(6) cells/24 h); this production, due to constitutive activation of NF-kappaB, is inhibited by agents like curcumin and dehydroxymethylepoxyquinomicin (DHMEQ), which interfere with the transcription factor. Flow cytometry, ELISA, mRNA, and Western blotting analyses were performed to characterize the status of the IL-6 receptor in HA22T/VGH cells. Two transmembrane glycoproteins that form the functional IL-6 receptor have been identified: the ligand-binding gp80 and the signal-transducer gp130. Soluble forms of gp80 also trigger membrane gp130 signaling when complexed with IL-6, while soluble forms of gp130 inhibit the same process. Our results showed that HA22T/VGH cells express gp130 at their surface, but release only traces of its soluble form. For gp80, the cells produced the mRNAs of both its membrane and soluble form. However, in immunoblotting they exhibited a very faint content of the same subunit, which, in addition, was neither expressed at the cell surface nor secreted. In MTT assays, incubation with a neutralizing anti-IL-6 antibody for up to 7 days did not affect the growth of HA22T/VGH cells. Also, other specific anti-IL-6 approaches (siRNA or AODN) failed to produce this result. In conclusion, autostimulatory loops mediated by IL-6 are less likely to occur in HCC than in other kinds of cancer. However, since release of IL-6 is frequent in HCC, especially in its more advanced stages, the use of agents like curcumin or DHMEQ might be beneficial to counteract its adverse systemic effects (e.g., cachexia).

Anti-interleukin-6 monoclonal antibody inhibits autoimmune responses in a murine model of systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is an autoimmune disease resulting from dysregulation of the immune system. Interleukin-6 (IL-6) is a multifunctional cytokine produced by macrophages, monocytes and T and B cells. It stimulates B-cell differentiation/maturation, immunoglobulin secretion, and T-cell functions. Elevated levels of IL-6 in serum, urine and renal glomeruli were detected in patients with active SLE and in murine models of SLE. Our study investigated the role of IL-6 in an SLE-like disease in New Zealand Black/White (NZB/W) F1 mice by administration of an anti-murine IL-6 monoclonal antibody (mAb). Intraperitoneal administration of the anti-IL-6 mAb suppressed the production of anti-dsDNA autoantibody. B-cell proliferation induced by anti-IgM and anti-CD40 was lower in the anti-IL-6 mAb-treated mice, ex vivo studies demonstrated that anti-IL-6 mAb treatment inhibited anti-dsDNA production. Anti-CD3-induced T-cell proliferation and mixed lymphocyte reactions were inhibited by anti-IL-6 mAb treatment, indicating a partial down-regulation of T cells. Histological analysis showed that treatment with anti-IL-6 mAb prevented the development of severe kidney disease. These results suggest that treatment with anti-IL-6 mAb has a beneficial effect on autoimmunity in murine SLE and that autoreactive B cells may be the primary target for anti-IL-6 mAb treatment; its effect on autoreactive T cells is also indicated.

Vitreous fluid biomarkers

Interactions between cells and the network of secreted proteins are associated with the ocular disease. In most cases, clinical appearcance is sufficiently diagnostic. However, in cases of nonspecific or atypical clinical presentation, diagnostic sampling of vitreous fluid can aid diagnosis and treatment for ocular disease. Progresses in the basic sciences, particularly molecular biology, and advances in surgical instrumentation have greatly enhanced the diagnostic armamentarium. These developments also have led to a better understanding of the pathophysiological processes involved in ocular diseases and have prompted evolution of new therapeutic modalities. In this chapter, we review techniques for vitreous fluid sampling and biomarker quantitation thereof. The molecular biology of bioactive vitreous fluid factors is also discussed with respect to their clinical involvement in the development of ocular disease.

Interleukin-6 and STAT3 protect the liver from hepatic ischemia and reperfusion injury during ischemic preconditioning

BACKGROUND

Ischemic preconditioning has been shown to protect the liver from ischemia/reperfusion injury. We hypothesized that IL-6 directly modulates the protective effects of ischemic preconditioning.

METHODS

Three weeks after undergoing splenic transposition, wild-type C57BL/6 and IL-6 null mice underwent 75 minutes of total hepatic ischemia with or without prior ischemic preconditioning (10 minutes of ischemia followed by 15 minutes of reperfusion). After reperfusion, serum ALT, serum IL-6, hepatic IL-6 mRNA, hepatic pSTAT3, and liver histology were evaluated.

RESULTS

In wild-type mice, survival at 24 hours was greater in the preconditioned group compared with the non-preconditioned group (75% vs 40%, P<.05). In IL-6 null mice, however, ischemic preconditioning did not improve survival when compared with the non-preconditioned group. Preconditioning significantly reduced hepatocellular injury in wild-type mice (P<.05) when compared with IL-6 null animals. This protection was associated with significant increases in serum IL-6, hepatic IL-6 mRNA, and hepatic pSTAT3 levels (P<.05). The protective effects of ischemic preconditioning that correlated with significant increases in systemic IL-6, hepatic IL-6 mRNA abundance, and pSTAT3 levels, were not observed in IL-6 null mice.

CONCLUSIONS

The protective effects of ischemic preconditioning during total hepatic ischemia/reperfusion injury are dependent on IL-6 signaling and are associated with increased phosphorylation of hepatic STAT3.

Interleukin-6 trans-signaling in inflammatory bowel disease

The pathogenesis of inflammatory bowel disease (IBD) is complex, involving a wide range of molecules including cytokines. Recent investigations support the important role of an interleukin-6 (IL-6) signaling pathway in the development of IBD. However, the molecular mechanisms of this pathway in the intestine remain incompletely understood. The circulating and intestinal levels of IL-6 as well as soluble IL-6 receptor (sIL-6R) are increased in patients with IBD. It is remarkable that the mucosal T cells of IBD patients are extremely resistant to apoptosis and that a large fraction of these cells express membrane-bound gp130 but not IL-6R. The accumulated evidence strongly supports the hypothesis that the development and perpetuation of IBD relies on the increased formation of IL-6/sIL-6R complexes interacting with membrane-bound gp130 on T cells via trans-signaling. These studies suggest that IL-6 trans-signaling may play a role in the development of IBD; they therefore imply the possibility of a selective therapeutic strategy to target this signaling.

Physical and functional interactions between Daxx and STAT3

Signal transducer and activator of transcription 3 (STAT3) play key roles in the intracellular signaling pathways of the interleukin (IL)-6 family of cytokines, which exhibit a diverse set of cellular responses, including cell proliferation and differentiation. Dysregulated IL-6/STAT3 signaling is involved in the pathogenesis of several diseases, for example autoimmune diseases and tumors. Type I interferon (IFN) induces the expression of proapoptotic genes and has been used in the clinical treatment of several tumors. In the present study, we found that type I IFN suppressed IL-6/STAT3-mediated transcription and gene expression. Furthermore, a type I IFN-induced protein, Daxx, also suppressed STAT3-mediated transcriptional activation, while overexpression of Daxx inhibited IL-6/STAT3-mediated gene expression. Importantly, small-interfering RNA-mediated reduction of Daxx expression enhanced IL-6/leukemia inhibitory factor (LIF)-induced STAT3-dependent transcription. Co-immunoprecipitation studies revealed a physical interaction between Daxx and STAT3 in transiently transfected 293T cells. We further found that Daxx and STAT3 were co-localized in the nucleus. These results indicate that Daxx may serve as a transcriptional regulator of type I IFN-mediated suppression of the IL-6/STAT3 signaling pathway.

Endogenous leukemia inhibitory factor production limits autoimmune demyelination and oligodendrocyte loss

Autoimmune injury to oligodendrocytes evokes an endogenous response in the central nervous system, which initially limits the acute injury to oligodendrocytes and myelin, and subsequently promotes remyelination. The key molecular and cellular events responsible for this beneficial outcome are incompletely understood. In this article, we utilize murine autoimmune encephalomyelitis (EAE) to focus on the effect of endogenously produced leukemia inhibitory factor (LIF) upon mature oligodendrocyte survival after demyelinating injury. We show that the mRNA for LIF is markedly upregulated in the spinal cord in the context of acute inflammatory demyelination. After clinical disease onset, administration of neutralizing anti-LIF antibodies over a four day period significantly worsens disease severity in two different murine EAE models. We also show that administration of neutralizing antibodies results in reduced activation of the cognate LIF receptor components in the spinal cord. Histologically, anti-LIF antibody administration increases the extent of acute demyelination (P < 0.01) and doubles the oligodendrocyte loss already induced by EAE (P < 0.05), without altering the extent of inflammatory infiltration into the spinal cord. Although acute EAE induces a rapid, three-fold increase in the proliferation of NG2 positive oligodendrocyte progenitors (P < 0.001), this response is not diminished by antagonism of endogenous LIF. We conclude that endogenous LIF is induced in response to autoimmune demyelination in the spinal cord and protects mature oligodendrocytes from demyelinating injury and cell death, thereby resulting in attenuation of clinical disease severity.

Inhibitory effect of chroman carboxamide on interleukin-6 expression in response to lipopolysaccharide by preventing nuclear factor-kappaB activation in macrophages

6-Hydroxy-7-methoxychroman-2-carboxylic acid (3-nitrophenyl)amide (CP-1158) is a synthetic chroman carboxamide with trolox-like chemical structure. In the present study, CP-1158 was found to inhibit interleukin (IL)-6 production in lipopolysaccharide (LPS)-stimulated macrophages RAW 264.7. The CP-1158 attenuated LPS-induced synthesis of IL-6 transcript but also inhibited LPS-induced IL-6 promoter activity. Further, CP-1158 attenuated LPS-induced syntheses of tumor necrosis factor (TNF)-alpha, IL-1beta, interferon-inducible protein (IP)-10 and macrophage inflammatory protein (MIP)-1beta transcripts. Nuclear factor (NF)-kappaB has been evidenced to play a major mechanism in LPS-induced expression of IL-6 or other inflammatory cytokines. CP-1158 prevented LPS-induced nuclear translocation of NF-kappaB complex and subsequently inhibited DNA binding activity of NF-kappaB complex as well as NF-kappaB transcriptional activity in macrophages RAW 264.7. However, CP-1158 did not affect LPS-induced phosphorylation and degradation of inhibitory kappaB (IkappaB). In another experiment, CP-1158 inhibited IL-6 promoter activity elicited by expression vectors encoding NF-kappaB p50 or p65 subunit. Taken together, CP-1158 inhibited LPS-induced expression of inflammatory cytokines including IL-6, targeting NF-kappaB activating pathway downstream IkappaB degradation, and thus could provide an anti-inflammatory potential of chroman carboxamide.

Autoimmune arthritis associated with mutated interleukin (IL)-6 receptor gp130 is driven by STAT3/IL-7-dependent homeostatic proliferation of CD4+ T cells

Mice homozygous for the F759 mutation in the gp130 interleukin (IL)-6 receptor subunit have enhanced gp130-mediated signal transducer and activator of transcription (STAT)3 activation and spontaneously developed a lymphocyte-mediated rheumatoid arthritis-like joint disease. Here, we show that the development of the disease is dependent on both major histocompatibility complex (MHC) II–restricted CD4⁺ T cells and IL-6 family cytokines. In spite of the necessity for CD4⁺ T cells, the gp130 mutation was only required in nonhemtopoietic cells for the disease. The gp130 mutation resulted in enhanced production of IL-7. Conditional knockout of STAT3 in nonlymphoid cells showed that the enhancement of IL-7 production was dependent on STAT3 activation by IL-6 family cytokines. Homeostatic proliferation of CD4⁺ T cells was enhanced in gp130 mutant mice and acceleration of homeostatic proliferation enhanced the disease, whereas the inhibition of homeostatic proliferation suppressed the disease. Anti–IL-7 antibody treatment inhibited not only the enhanced homeostatic proliferation, but also the disease in gp130 mutant mice. Thus, our results show that autoimmune disease in gp130 mutant mice is caused by increased homeostatic proliferation of CD4⁺ T cells, which is due to elevated production of IL-7 by nonhematopoietic cells as a result of IL-6 family cytokine-gp130-STAT3 signaling.