15-deoxy-Delta12,14-prostaglandin J2 negatively regulates rankl gene expression in activated T lymphocytes: role of NF-kappaB and early growth response transcription factors

The POU-Domain Transcription Factor Oct-6/POU3F1 as a Regulator of Cellular Response to Genotoxic Stress

DNA damage and the generation of reactive oxygen species (ROS) are key mechanisms of apoptotic cell death by commonly used genotoxic drugs. However, the complex cellular response to these pharmacologic agents remains yet to be fully characterized. Several studies have described the role of transcription factor octamer-1 (Oct-1)/Pit-1, Oct-1/2, and Unc-86 shared domain class 2 homeobox 1 (POU2F1) in the regulation of the genes important for cellular response to genotoxic stress. Evaluating the possible involvement of other POU family transcription factors in these pathways, we revealed the inducible expression of Oct-6/POU3F1, a regulator of neural morphogenesis and epidermal differentiation, in cancer cells by genotoxic drugs. The induction of Oct-6 occurs at the transcriptional level via reactive oxygen species (ROS) and ataxia telangiectasia mutated- and Rad3-related (ATR)-dependent mechanisms, but in a p53 independent manner. Moreover, we provide evidence that Oct-6 may play a role in the regulation of cellular response to DNA damaging agents. Indeed, by using the shRNA approach, we demonstrate that in doxorubicin-treated H460 non-small-cell lung carcinoma (NSCLC) cells, Oct-6 depletion leads to a reduced G2-cell cycle arrest and senescence, but also to increased levels of intracellular ROS and DNA damage. In addition, we could identify p21 and catalase as Oct-6 target genes possibly mediating these effects. These results demonstrate that Oct-6 is expressed in cancer cells after genotoxic stress, and suggests its possible role in the control of ROS, DNA damage response (DDR), and senescence.

NF-κB-dependent RANKL expression in a mouse model of immature T-cell leukemia

Activation of the receptor activator of nuclear factor-κB (RANK) by its ligand (RANKL) is involved in both solid and hematological malignancies, including multiple myeloma, acute myeloid leukemia and B-cell leukemia. Although RANKL expression has been described in normal T cells, a potential role in T-cell leukemia remains undefined. Here, we used a model of immature T-cell leukemia/lymphoma, the TEL-JAK2 transgenic mice, to assess RANKL expression in leukemic cells and its regulatory mechanisms. We found that Rankl mRNA was significantly overexpressed in leukemic T cells when compared to wild-type thymocytes, their nonmalignant counterparts. Moreover, Rankl mRNA and RANKL surface expression in leukemic cells was induced by T-cell receptor (TCR) signaling activation, dependently on the NF-κB signaling pathway. These results indicate that TCR-activated leukemic T cells express high levels of RANKL and are potential inducers of RANK signaling in microenvironmental cells.

Effects of rheumatoid arthritis associated transcriptional changes on osteoclast differentiation network in the synovium

Background

Osteoclast differentiation in the inflamed synovium of rheumatoid arthritis (RA) affected joints leads to the formation of bone lesions. Reconstruction and analysis of protein interaction networks underlying specific disease phenotypes are essential for designing therapeutic interventions. In this study, we have created a network that captures signal flow leading to osteoclast differentiation. Based on transcriptome analysis, we have indicated the potential mechanisms responsible for the phenotype in the RA affected synovium.

Method

We collected information on gene expression, pathways and protein interactions related to RA from literature and databases namely Gene Expression Omnibus, Kyoto Encyclopedia of Genes and Genomes pathway and STRING. Based on these information, we created a network for the differentiation of osteoclasts. We identified the differentially regulated network genes and reported the signaling that are responsible for the process in the RA affected synovium.

Result

Our network reveals the mechanisms underlying the activation of the neutrophil cytosolic factor complex in connection to osteoclastogenesis in RA. Additionally, the study reports the predominance of the canonical pathway of NF-κB activation in the diseased synovium. The network also confirms that the upregulation of T cell receptor signaling and downregulation of transforming growth factor beta signaling pathway favor osteoclastogenesis in RA. To the best of our knowledge, this is the first comprehensive protein–protein interaction network describing RA driven osteoclastogenesis in the synovium.

Discussion

This study provides information that can be used to build models of the signal flow involved in the process of osteoclast differentiation. The models can further be used to design therapies to ameliorate bone destruction in the RA affected joints.

Genotoxic stress modulates the release of exosomes from multiple myeloma cells capable of activating NK cell cytokine production: Role of HSP70/TLR2/NF-kB axis

Exosomes are a class of nanovesicles formed and released through the late endosomal compartment and represent an important mode of intercellular communication. The ability of anticancer chemotherapy to enhance the immunogenic potential of malignant cells mainly relies on the establishment of the immunogenic cell death (ICD) and the release of damage-associated molecular patterns (DAMPs). Here, we investigated whether genotoxic stress could promote the release of exosomes from multiple myeloma (MM) cells and studied the immunomodulatory properties they exert on NK cells, a major component of the antitumor immune response playing a key role in the immunosurveillance of MM. Our findings show that melphalan, a genotoxic agent used in MM therapy, significantly induces an increased exosome release from MM cells. MM cell-derived exosomes are capable of stimulating IFNγ production, but not the cytotoxic activity of NK cells through a mechanism based on the activation of NF-κB pathway in a TLR2/HSP70-dependent manner. Interestingly, HSP70+ exosomes are primarily found in the bone marrow (BM) of MM patients suggesting that they might have a crucial immunomodulatory action in the tumor microenvironment. We also provide evidence that the CD56high NK cell subset is more responsive to exosome-induced IFNγ production mediated by TLR2 engagement. All together, these findings suggest a novel mechanism of synergism between chemotherapy and antitumor innate immune responses based on the drug-promotion of nanovesicles exposing DAMPs for innate receptors.

Characterization and application of two RANK-specific antibodies with different biological activities

Antibodies play an important role in therapy and investigative biomedical research. The TNF-family member Receptor Activator of NF-κB (RANK) is known for its role in bone homeostasis and is increasingly recognized as a central player in immune regulation and epithelial cell activation. However, the study of RANK biology has been hampered by missing or insufficient characterization of high affinity tools that recognize RANK. Here, we present a careful description and comparison of two antibodies, RANK-02 obtained by phage display (Newa, 2014 [1]) and R12-31 generated by immunization (Kamijo, 2006 [2]). We found that both antibodies recognized mouse RANK with high affinity, while RANK-02 and R12-31 recognized human RANK with high and lower affinities, respectively. Using a cell apoptosis assay based on stimulation of a RANK:Fas fusion protein, and a cellular NF-κB signaling assay, we showed that R12-31 was agonist for both species. R12-31 interfered little or not at all with the binding of RANKL to RANK, in contrast to RANK-02 that efficiently prevented this interaction. Depending on the assay and species, RANK-02 was either a weak agonist or a partial antagonist of RANK. Both antibodies recognized human Langerhans cells, previously shown to express RANK, while dermal dendritic cells were poorly labeled. In vivo R12-31 agonist activity was demonstrated by its ability to induce the formation of intestinal villous microfold cells in mice. This characterization of two monoclonal antibodies should now allow better evaluation of their application as therapeutic reagents and investigative tools.

Transcriptional regulation of the human TNFSF11 gene in T cells via a cell type-selective set of distal enhancers

In addition to osteoblast lineage cells, the TNF-like factor receptor activator of NF-κB ligand (RANKL) is expressed in both B and T cells and may play a role in bone resorption. Rankl gene (Tnfsf11) expression in mouse T cells is mediated through multiple distal elements marked by increased transcription factor occupancy, histone tail acetylation, and RNA polymerase II recruitment. Little is known, however, of the regulation of human TNFSF11 in T cells. Accordingly, we examined the consequence of T cell activation on the expression of this factor both in Jurkat cells and in primary human T cells. We then explored the mechanism of this regulation by scanning over 400 kb of DNA surrounding the TNFSF11 locus for regulatory enhancers using ChIP-chip analysis. Histone H3/H4 acetylation enrichment identified putative regulatory regions located between -170 and -220 kb upstream of the human TNFSF11 TSS that we designated the human T cell control region (hTCCR). This region showed high sequence conservation with the mouse TCCR. Inhibition of MEK1/2 by U0126 resulted in decreased RANKL expression suggesting that stimulation through MEK1/2 was a prerequisite. ChIP-chip analysis also revealed that c-FOS was recruited to the hTCCR as well. Importantly, both the human TNFSF11 D5a/b (RLD5a/b) enhancer and segments of the hTCCR mediated robust inducible reporter activity following TCR activation. Finally, SNPs implicated in diseases characterized by dysregulated BMD co-localized to the hTCCR region. We conclude that the hTCCR region contains a cell-selective set of enhancers that plays an integral role in the transcriptional regulation of the TNFSF11 gene in human T cells.

The functions of the avian receptor activator of NF-κB ligand (RANKL) and its receptors, RANK and osteoprotegerin, are evolutionarily conserved

A new member of the chicken TNF superfamily has recently been identified, namely receptor activator of NF-κB ligand (RANKL), as have its signalling receptor, RANK, and its decoy receptor, osteoprotegerin (OPG). In mammals, RANKL and RANK are transmembrane proteins expressed on the surface of Th1 cells and dendritic cells (DC) respectively, whereas OPG is expressed as a soluble protein from osteoblasts and DC. Recombinant soluble chicken RANKL (chRANKL) forms homotrimers whereas chicken OPG (chOPG) forms homodimers, characteristic of these molecules in mammals. ChRANKL, chRANK and chOPG are expressed at the mRNA level in most tissues and organs. ChRANKL is transcriptionally regulated by Ca(2+) mobilisation and enhances the mRNA expression levels of pro-inflammatory cytokines in bone marrow-derived DC (BMDC); this is inhibited by both chOPG-Fc and soluble chRANK-Fc. However, chRANKL does not enhance the expression of cell surface markers in either BMDC or BM-derived macrophages (BMM). Furthermore, chRANKL enhances the survival of APC similar to its mammalian orthologue.

To Live or to Die: Prosurvival Activity of PPARgamma in Cancers

The role of PPARγ in tumorigenesis is controversial. In this article, we review and analyze literature from the past decade that highlights the potential proneoplastic activity of PPARγ. We discuss the following five aspects of the nuclear hormone receptor and its agonists: (1) relative expression of PPARγ in human tumor versus normal tissues; (2) receptor-dependent proneoplastic effects; (3) impact of PPARγ and its agonists on tumors in animal models; (4) clinical trials of thiazolidinediones (TZDs) in human malignancies; (5) TZDs as chemopreventive agents in epidemiology studies. The focus is placed on the most relevant in vivo animal models and human data. In vitro cell line studies are included only when the effects are shown to be dependent on the PPARγ receptor.

Mouse Rankl expression is regulated in T cells by c-Fos through a cluster of distal regulatory enhancers designated the T cell control region

Receptor activator of NF-κB ligand (Rankl) is a TNF-like factor that induces the formation of osteoclasts responsible for bone resorption. Although T cell activation up-regulates this gene, the molecular mechanism of its transcriptional control remains unknown. We used ChIP-chip analysis in mouse primary T cells and a T cell hybridoma to define the regulatory enhancers responsible for this up-regulation and to characterize their properties. Elevated H3/H4 acetylation and increased RNA polymerase II density were evident at mRL-D5, a known enhancer located 76 kb upstream of the TSS, as well as at a cluster of regulatory sites located even further upstream between -123 to -156 kb, termed the T cell control region (TCCR). Based upon the ability of calcium signaling and MAPK inhibitors to block Rankl expression, we conducted further ChIP-chip analysis of the transcriptional mediators c-Fos, NF-κB, and Nfat. T cell activation induced c-Fos binding at the mRL-D5 enhancer and within the TCCR. The interaction of NF-κB was observed at the transcriptional start site and at mRL-D5. Both mRL-D5 and segments of the TCCR exhibited robust transcriptional activity in reporter assays, and site-specific mutagenesis of c-Fos and Nfat elements abrogated reporter activity, suggesting a role for both factors in the control of enhancer-mediated Rankl transcription. Finally, chromosome conformation capture analysis confirmed that mRL-D5 and segments of the TCCR were located in proximity to the Rankl gene promoter and thus potentially able to influence directly Rankl gene promoter activity. We conclude that both mRL-D5 and the TCCR represent control segments that play an integral role in Rankl expression in T cells.

Control of RANKL gene expression

Osteoclasts are highly specialized cells capable of degrading mineralized tissue and form at different regions of bone to meet different physiological needs, such as mobilization of calcium, modeling of bone structure, and remodeling of bone matrix. Osteoclast production is elevated in a number of pathological conditions, many of which lead to loss of bone mass. Whether normal or pathological, osteoclastogenesis strictly depends upon support from accessory cells which supply cytokines required for osteoclast differentiation. Only one of these cytokines, receptor activator of NFkappaB ligand (RANKL), is absolutely essential for osteoclast formation throughout life and is thus expressed by all cell types that support osteoclast differentiation. The central role of RANKL in bone resorption is highlighted by the fact that it is the basis for a new therapy to inhibit bone loss. This review will discuss mechanisms that control RANKL gene expression in different osteoclast-support cells and how the study of such mechanisms may lead to a better understanding of the cellular interactions that drive normal and pathological bone resorption.

Mechanisms for how inhaled multiwalled carbon nanotubes suppress systemic immune function in mice

The potential health effects of inhaling carbon nanotubes are important because of possible exposures in occupational settings. Previously, we have shown mice that have inhaled multiwalled carbon nanotubes have suppressed systemic immune function. Here, we show the mechanisms for this immune suppression. Mice were exposed to 0, 0.3 or 1 mg m(-3) multiwalled carbon nanotubes for 6 h per day for 14 consecutive days in whole-body inhalation chambers. Only those exposed to a dose of 1 mg m(-3) presented suppressed immune function; this involved activation of cyclooxygenase enzymes in the spleen in response to a signal from the lungs. Spleen cells from exposed animals partially recovered their immune function when treated with ibuprofen, a drug that blocks the formation of cyclooxygenase enzymes. Knockout mice without cyclooxygenase enzymes were not affected when exposed to multiwalled carbon nanotubes, further confirming the importance of this enzyme in suppression. Proteins from the lungs of exposed mice suppressed the immune function of spleen cells from normal mice, but not those from knockout mice. Our findings suggest that signals from the lung can activate signals in the spleen to suppress the immune function of exposed mice.

NF-kappaB inhibitor dehydroxymethylepoxyquinomicin suppresses osteoclastogenesis and expression of NFATc1 in mouse arthritis without affecting expression of RANKL, osteoprotegerin or macrophage colony-stimulating factor

Inhibition of NF-κB is known to be effective in reducing both inflammation and bone destruction in animal models of arthritis. Our previous study demonstrated that a small cell-permeable NF-κB inhibitor, dehydroxymethylepoxyquinomicin (DHMEQ), suppresses expression of proinflammatory cytokines and ameliorates mouse arthritis. It remained unclear, however, whether DHMEQ directly affects osteoclast precursor cells to suppress their differentiation to mature osteoclasts in vivo. The effect of DHMEQ on human osteoclastogenesis also remained elusive. In the present study, we therefore examined the effect of DHMEQ on osteoclastogenesis using a mouse collagen-induced arthritis model, and using culture systems of fibroblast-like synovial cells obtained from patients with rheumatoid arthritis, and of osteoclast precursor cells from peripheral blood of healthy volunteers. DHMEQ significantly suppressed formation of osteoclasts in arthritic joints, and also suppressed expression of NFATc1 along the inner surfaces of bone lacunae and the eroded bone surface, while serum levels of soluble receptor activator of NF-κB ligand (RANKL), osteoprotegerin and macrophage colony-stimulating factor were not affected by the treatment. DHMEQ also did not suppress spontaneous expression of RANKL nor of macrophage colony-stimulating factor in culture of fibroblast-like synovial cells obtained from patients with rheumatoid arthritis. These results suggest that DHMEQ suppresses osteoclastogenesis in vivo, through downregulation of NFATc1 expression, without significantly affecting expression of upstream molecules of the RANKL/receptor activator of NF-κB/osteoprotegerin cascade, at least in our experimental condition. Furthermore, in the presence of RANKL and macrophage colony-stimulating factor, differentiation and activation of human osteoclasts were also suppressed by DHMEQ, suggesting the possibility of future application of NF-κB inhibitors to rheumatoid arthritis therapy.

Inhibition of trail gene expression by cyclopentenonic prostaglandin 15-deoxy-delta12,14-prostaglandin J2 in T lymphocytes

15-Deoxy-Delta(12,14)-prostaglandin J(2) (15d-PGJ(2)) is a cyclopentenonic prostaglandin endowed with powerful anti-inflammatory activities, as shown in animal models of inflammatory/autoimmune diseases, where pharmacological administration of this prostanoid can ameliorate inflammation and local tissue damage via activation of the nuclear receptor peroxisome proliferator-activated receptor gamma (PPARgamma) and/or covalent modifications of cellular proteins. Tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) is a member of the TNF superfamily expressed in most of the cells, including those of immune system such as T lymphocytes, in which it is up-regulated upon antigen-specific stimulation. This cytokine plays an important role in regulating various physiological and immunopathological processes, such as immunosurveillance of tumors and tissue destruction associated with different inflammatory and autoimmune diseases. Here, we demonstrate that 15d-PGJ(2) inhibits trail mRNA and protein expression by down-regulating the activity of its promoter in human T lymphocytes. Our data indicate that both the chemically reactive cyclopentenone moiety of 15d-PGJ(2) and the activation of PPARgamma may be involved in this repressive mechanism. We identified nuclear factor kappaB (NF-kappaB) as a direct target of the prostanoid. 15d-PGJ(2) significantly decreases the expression and/or DNA binding of c-rel, RelA, and p50 transcription factors to the NF-kappaB1 site of trail promoter. Moreover, 15d-PGJ(2)-mediated activation of the transcription factor heat shock factor-1 may contribute to inhibit trail promoter activity in transfected Jurkat T cells. These results suggest that modulation of TRAIL gene expression by 15d-PGJ(2) in T cells may provide a novel pharmacological tool to modify the onset and the progression of specific autoimmune and inflammatory disorders.