A lipopolysaccharide-specific enhancer complex involving Ets, Elk-1, Sp1, and CREB binding protein and p300 is recruited to the tumor necrosis factor alpha promoter in vivo

CREB binding protein (CBP) activation is required for luteinizing hormone beta expression and normal fertility in mice

Normal function of the hypothalamic-pituitary-gonadal axis is dependent on gonadotropin-releasing hormone (GNRH)-stimulated synthesis and secretion of luteinizing hormone (LH) from the pituitary gonadotroph. While the transcriptional coactivator CREB binding protein (CBP) is known to interact with Egr-1, the major mediator of GNRH action on the Lhb gene, the role of CBP in Lhb gene expression has yet to be characterized. We show that in the LβT2 gonadotroph cell line, overexpression of CBP augmented the response to GNRH and that knockdown of CBP eliminated GNRH responsiveness. While GNRH-mediated phosphorylation of CBP at Ser436 increased the interaction with Egr-1 on the Lhb promoter, loss of this phosphorylation site eliminated GNRH-mediated Lhb expression in LβT2 cells. In vivo, loss of CBP phosphorylation at Ser436 rendered female mice subfertile. S436A knock-in mice had disrupted estrous cyclicity and reduced responsiveness to GNRH. Our results show that GNRH-mediated phosphorylation of CBP at Ser436 is required for Egr-1 to activate Lhb expression and is a requirement for normal fertility in female mice. As CBP can be phosphorylated by other factors, such as insulin, our studies suggest that CBP may act as a key regulator of Lhb expression in the gonadotroph by integrating homeostatic information with GNRH signaling.

Redox signaling and histone acetylation in acute pancreatitis

Histone acetylation via CBP/p300 coordinates the expression of proinflammatory cytokines in the activation phase of inflammation, particularly through mitogen-activated protein kinases (MAPKs), nuclear factor-κB (NF-κB), and signal transducers and activators of transcription (STAT) pathways. In contrast, histone deacetylases (HDACs) and protein phosphatases are mainly involved in the attenuation phase of inflammation. The role of reactive oxygen species (ROS) in the inflammatory cascade is much more important than expected. Mitochondrial ROS act as signal-transducing molecules that trigger proinflammatory cytokine production via inflammasome-independent and inflammasome-dependent pathways. The major source of ROS in acute inflammation seems to be NADPH oxidases, whereas NF-κB, protein phosphatases, and HDACs are the major targets of ROS and redox signaling in this process. There is a cross-talk between oxidative stress and proinflammatory cytokines through serine/threonine protein phosphatases, tyrosine protein phosphatases, and MAPKs that greatly contributes to amplification of the uncontrolled inflammatory cascade and tissue injury in acute pancreatitis. Chromatin remodeling during induction of proinflammatory genes would depend primarily on phosphorylation of transcription factors and their binding to gene promoters together with recruitment of histone acetyltransferases. PP2A should be considered a key modulator of the inflammatory cascade in acute pancreatitis through the ERK/NF-κB pathway and histone acetylation.

Monocyte-specific accessibility of a matrix attachment region in the tumor necrosis factor locus

Regulation of TNF gene expression is cell type- and stimulus-specific. We have previously identified highly conserved noncoding regulatory elements within DNase I-hypersensitive sites (HSS) located 9 kb upstream (HSS-9) and 3 kb downstream (HSS+3) of the TNF gene, which play an important role in the transcriptional regulation of TNF in T cells. They act as enhancers and interact with the TNF promoter and with each other, generating a higher order chromatin structure. Here, we report a novel monocyte-specific AT-rich DNase I-hypersensitive element located 7 kb upstream of the TNF gene (HSS-7), which serves as a matrix attachment region in monocytes. We show that HSS-7 associates with topoisomerase IIα (Top2) in vivo and that induction of endogenous TNF mRNA expression is suppressed by etoposide, a Top2 inhibitor. Moreover, Top2 binds to and cleaves HSS-7 in in vitro analysis. Thus, HSS-7, which is selectively accessible in monocytes, can tether the TNF locus to the nuclear matrix via matrix attachment region formation, potentially promoting TNF gene expression by acting as a Top2 substrate.

The dysregulation of the monocyte/macrophage effector function induced by isopropanol is mediated by the defective activation of distinct members of the AP-1 family of transcription factors

Isopropanol is the second most common cause of short-chain alcohol acute intoxication. Nonethanolic short-chain alcohols mediate their immunomodulatory effect by interfering with nuclear factor of activated T cells (NFAT) activation with or without additional activator protein-1 (AP-1) involvement. In the present study, we examined the immunomodulation induced by isopropanol in conditions that are not reliant on NFAT: the inflammatory cytokine response of lipopolysaccharide (LPS)-stimulated monocytes. Our hypothesis was that isopropanol acute exposure would have an attenuated effect or no consequence in this setting. To our surprise, the impairment of AP-1 activation was sufficient to mediate a severe and dose-dependent phenotype in human monocytes in vitro at alcohol concentrations as low as 0.16% (or 26 mM). There were three outcomes: interleukin (IL)-1β/IL-8 were unaltered; IL-6 was upregulated; and tumor necrosis factor alpha (TNF-α)/CCL2 were downregulated. The effector function of human monocyte-derived macrophages was also compromised. Our results showed that Toll-like receptor 4 early signaling was preserved, as isopropanol did not change the kinase activity of the IL-1 receptor-associated kinase 1 in LPS-stimulated cells. The nuclear factor-κB signaling cascade and the p38/c-Jun N-terminal kinase modules of the mitogen-activated protein kinase pathway were alcohol insensitive. Conversely, the activation of extracellular signal-regulated protein kinase and, ultimately, of c-Fos and JunB were impaired. The alcohol-induced cytokine dysregulation was confirmed in a mouse model of isopropanol intoxication in which the production of TNF-α in response to LPS challenge was virtually abolished. The magnitude of this alcohol effect was sufficiently high to rescue animals from LPS-induced toxic shock. Our data contribute to the dismal body of information on the immunotoxicology of isopropanol, one of the most ubiquitous chemicals to which the general population is significantly exposed.

Arc of a vicious circle: pathways activated by Mycobacterium tuberculosis that target the HIV-1 long terminal repeat

In this review, we examine how a subset of signal transduction cascades initiated by Mycobacterium tuberculosis (Mtb) infection modulates transcription mediated by the human immunodeficiency virus type 1 long terminal repeat (HIV-1 LTR). We describe two distinct phases of signaling that target transcription factors known to bind the HIV-1 LTR, and thus drive viral transcription and replication, in cells of the Mtb-infected host. First, Mtb-derived molecules, including cell wall components and DNA, interact with a number of host pattern recognition receptors. Second, cytokines and chemokines secreted in response to Mtb infection initiate signal transduction cascades through their cognate receptors. Given the variation in cell wall components among distinct clinical Mtb strains, the initial pattern recognition receptor interaction leading to direct LTR activation and differential cytokine and chemokine production is likely to be an important aspect of Mtb strain-specific regulation of HIV-1 transcription and replication. Improved understanding of these molecular mechanisms in the context of bacterial and host genetics should provide key insights into the accelerated viral replication and disease progression characteristic of HIV/TB coinfection.

Nuclear presence of nuclear factor of activated T cells (NFAT) c3 and c4 is required for Toll-like receptor-activated innate inflammatory response of monocytes/macrophages

Nuclear factor of activated T cells (NFATs) are crucial transcription factors that tightly control proinflammatory cytokine expression for adaptive immunity in T and B lymphocytes. However, little is known about the role of NFATs for innate immunity in macrophages. In this study, we report that NFAT is required for Toll-like receptor (TLR)-initiated innate immune responses in bone marrow-derived macrophages (BMMs). All TLR ligand stimulation including LPS, a TLR4 ligand, and Pam(3)CSK(4), a TLR1/2 ligand, induced expression of TNF which was inhibited by VIVIT, an NFAT-specific inhibitor peptide. BMMs from NFATc4 knock-out mouse expressed less TNF than wild type. Despite apparent association between NFAT and TNF, LPS did not directly activate NFAT based on NFAT-luciferase reporter assay, whereas NF-κB was inducibly activated by LPS. Instead, macrophage exhibited constitutive NFAT activity which was not increased by LPS and was decreased by VIVIT. Immunocytochemical examination of NFATc1-4 of BMMs exhibited nuclear localization of NFATc3/c4 regardless of LPS stimulation. LPS stimulation did not cause nuclear translocation of NFATc1/c2. Treatment with VIVIT resulted in nuclear export of NFATc3/c4 and inhibited TLR-activated TNF expression, suggesting that nuclear residence of NFATc is required for TLR-related innate immune response. Chromatin immunoprecipitation (ChIP) assay using anti-RNA polymerase II (PolII) antibody suggested that VIVIT decreased PolII binding to TNF gene locus, consistent with VIVIT inhibition of LPS-induced TNF mRNA expression. This study identifies a novel paradigm of innate immune regulation rendered by NFAT which is a well known family of adaptive immune regulatory proteins.

Inflammatory gene regulatory networks in amnion cells following cytokine stimulation: translational systems approach to modeling human parturition

A majority of the studies examining the molecular regulation of human labor have been conducted using single gene approaches. While the technology to produce multi-dimensional datasets is readily available, the means for facile analysis of such data are limited. The objective of this study was to develop a systems approach to infer regulatory mechanisms governing global gene expression in cytokine-challenged cells in vitro, and to apply these methods to predict gene regulatory networks (GRNs) in intrauterine tissues during term parturition. To this end, microarray analysis was applied to human amnion mesenchymal cells (AMCs) stimulated with interleukin-1β, and differentially expressed transcripts were subjected to hierarchical clustering, temporal expression profiling, and motif enrichment analysis, from which a GRN was constructed. These methods were then applied to fetal membrane specimens collected in the absence or presence of spontaneous term labor. Analysis of cytokine-responsive genes in AMCs revealed a sterile immune response signature, with promoters enriched in response elements for several inflammation-associated transcription factors. In comparison to the fetal membrane dataset, there were 34 genes commonly upregulated, many of which were part of an acute inflammation gene expression signature. Binding motifs for nuclear factor-κB were prominent in the gene interaction and regulatory networks for both datasets; however, we found little evidence to support the utilization of pathogen-associated molecular pattern (PAMP) signaling. The tissue specimens were also enriched for transcripts governed by hypoxia-inducible factor. The approach presented here provides an uncomplicated means to infer global relationships among gene clusters involved in cellular responses to labor-associated signals.

Calcium input potentiates the transforming growth factor (TGF)-beta1-dependent signaling to promote the export of inorganic pyrophosphate by articular chondrocyte

Transforming growth factor (TGF)-β1 stimulates extracellular PP(i) (ePP(i)) generation and promotes chondrocalcinosis, which also occurs secondary to hyperparathyroidism-induced hypercalcemia. We previously demonstrated that ANK was up-regulated by TGF-β1 activation of ERK1/2 and Ca(2+)-dependent protein kinase C (PKCα). Thus, we investigated mechanisms by which calcium could affect ePP(i) metabolism, especially its main regulating proteins ANK and PC-1 (plasma cell membrane glycoprotein-1). We stimulated articular chondrocytes with TGF-β1 under extracellular (eCa(2+)) or cytosolic Ca(2+) (cCa(2+)) modulations. We studied ANK, PC-1 expression (quantitative RT-PCR, Western blotting), ePP(i) levels (radiometric assay), and cCa(2+) input (fluorescent probe). Voltage-operated Ca(2+)-channels (VOC) and signaling pathways involved were investigated with selective inhibitors. Finally, Ank promoter activity was evaluated (gene reporter). TGF-β1 elevated cCa(2+) and ePP(i) levels (by up-regulating Ank and PC-1 mRNA/proteins) in an eCa(2+) dose-dependent manner. TGF-β1 effects were suppressed by cCa(2+) chelation or L- and T-VOC blockade while being mostly reproduced by ionomycin. In the same experimental conditions, the activation of Ras, the phosphorylation of ERK1/2 and PKCα, and the stimulation of Ank promoter activity were affected similarly. Activation of SP1 (specific protein 1) and ELK-1 (Ets-like protein-1) transcription factors supported the regulatory role of Ca(2+). SP1 or ELK-1 overexpression or blockade experiments demonstrated a major contribution of ELK-1, which acted synergistically with SP1 to activate Ank promoter in response to TGF-β1. TGF-β1 promotes input of eCa(2+) through opening of L- and T-VOCs, to potentiate ERK1/2 and PKCα signaling cascades, resulting in an enhanced activation of Ank promoter and ePP(i) production in chondrocyte.

Earliest innate immune responses require macrophage RelA during pneumococcal pneumonia

NF-κB regulates cytokine expression to initiate and control the innate immune response to lung infections. The NF-κB protein RelA is critical for pulmonary host defense during Streptococcus pneumoniae pneumonia, but the cell-specific roles of this transcription factor remain to be determined. We hypothesized that RelA in alveolar macrophages contributes to cytokine expression and host defense during pneumococcal pneumonia. To test this hypothesis, we compared mice lacking RelA exclusively in myeloid cells (RelA(Δ/Δ)) with littermate controls (RelA(F/F)). Alveolar macrophages from RelA(Δ/Δ) mice expressed no full-length RelA, demonstrating effective targeting. Alveolar macrophages from RelA(Δ/Δ) mice exhibited reduced, albeit detectable, proinflammatory cytokine responses to S. pneumoniae, compared with alveolar macrophages from RelA(F/F) mice. Concentrations of these cytokines in lung homogenates were diminished early after infection, indicating a significant contribution of macrophage RelA to the initial expression of cytokines in the lungs. However, the cytokine content in infected lungs was equivalent by 15 hours. Neutrophil recruitment during S. pneumoniae pneumonia reflected a delayed onset in RelA(Δ/Δ) mice, followed by similar rates of accumulation. Bacterial clearance was eventually effective in both genotypes, but began later in RelA(Δ/Δ) mice. Thus, during pneumococcal pneumonia, only the earliest induction of the cytokines measured depended on transcription by RelA in myeloid cells, and this transcriptional activity contributed to effective immunity.

Tetra-O-methyl nordihydroguaiaretic acid (Terameprocol) inhibits the NF-κB-dependent transcription of TNF-α and MCP-1/CCL2 genes by preventing RelA from binding its cognate sites on DNA

Background

Tetra-O-methyl nordihydroguaiaretic acid, also known as terameprocol (TMP), is a naturally occurring phenolic compound found in the resin of the creosote bush. We have shown previously that TMP will suppress production of certain inflammatory cytokines, chemokines and lipids from macrophages following stimulation with LPS or infection with H1N1 influenza virus. In this study our goal was to elucidate the mechanism underlying TMP-mediated suppression of cytokine and chemokine production. We focused our investigations on the response to LPS and the NF-κB protein RelA, a transcription factor whose activity is critical to LPS-responsiveness.

Methods

Reporter assays were performed with HEK293 cells overexpressing either TLR-3, -4, or -8 and a plasmid containing the luciferase gene under control of an NF-κB response element. Cells were then treated with LPS, poly(I:C), or resiquimod, and/or TMP, and lysates measured for luciferase activity.

RAW 264.7 cells treated with LPS and/or TMP were used in ChIP and EMSA assays. For ChIP assays, chromatin was prepared and complexes precipitated with anti-NF-κB RelA Ab. Cross-links were reversed, DNA purified, and sequence abundance determined by Q-PCR. For EMSA assays, nuclear extracts were incubated with radiolabeled probes, analyzed by non-denaturing PAGE and visualized by autoradiography.

RAW 264.7 cells treated with LPS and/or TMP were also used in fluorescence microscopy and western blot experiments. Translocation experiments were performed using a primary Ab to NF-κB RelA and a fluorescein-conjugated secondary Ab. Western blots were performed using Abs to IκB-α and phospho-IκB-α. Bands were visualized by chemiluminescence.

Results

In reporter assays with TLR-3, -4, and -8 over-expressing cells, TMP caused strong inhibition of NF-κB-dependent transcription.

ChIP assays showed TMP caused virtually complete inhibition of RelA binding in vivo to promoters for the genes for TNF-α, MCP-1/CCL2, and RANTES/CCL5 although the LPS-dependent synthesis of IκB-α was not inhibited. EMSA assays did not reveal an effect of TMP on the binding of RelA to naked DNA templates in vitro.

TMP did not inhibit the nuclear translocation of NF-κB RelA nor the phosphorylation of IκB-α.

Conclusion

TMP acts indirectly as an inhibitor of NF-κB-dependent transcription by preventing RelA from binding the promoters of certain key cytokine and chemokine genes.

The P2X7-Egr pathway regulates nucleotide-dependent inflammatory gene expression in microglia

Microglial hyperactivity contributes to neuronal damage resulting from CNS injury and disease. Therefore, a better understanding of endogenous microglial receptor systems that can be exploited to modulate their inflammatory functions is important if better, neuroprotective therapeutics are to be designed. Previous studies from our lab and others have demonstrated that the P2X7 purinergic receptor agonist BzATP attenuates microglial inflammatory mediator production stimulated by lipopolysaccharide (LPS), suggesting that purinergic receptors may be one such receptor system that can be used for manipulating microglial activation. However, although P2X7 receptor activation is well recognized to regulate processing and release of cytokines, little is known concerning its role in regulating the transcription of inflammatory genes, nor the molecular mechanisms underlying these transcriptional effects. In the present studies, we identify that the transcription factors early growth response (Egr)-1, -2 and -3 are downstream signaling targets of P2X7 receptors in microglia, and that their activation is sensitive to MEK and p38 mitogen-activated protein kinase (MAPK) inhibitors. Moreover, using RNAi, we demonstrate that Egr factors and P2X7 receptors are necessary for BzATP-mediated attenuation of iNOS, and stimulation of TNF-α and IL-6 gene expression. BzATP also attenuates neuronal death induced by LPS conditioned medium, and P2X7 receptors are required for this effect. These studies are the first to identify Egr factors as regulators of inflammatory gene expression following P2X7 receptor activation, and suggest that P2X7 receptors may utilize the MAPK-Egr pathway to exert differential effects on microglial inflammatory activities which are beneficial to neuron survival.

Febrile range temperature represses TNF-alpha gene expression in LPS-stimulated macrophages by selectively blocking recruitment of Sp1 to the TNF-alpha promoter

We have previously shown that exposure to febrile-range temperature (FRT, 39.5 degrees C) reduces LPS-induced TNF-alpha transcription in mouse macrophages through at least two mechanisms: (1) by directly recruiting heat shock factor-1 (HSF-1) to a heat shock response element present in the TNF-alpha 5'-UTR and (2) by markedly reducing LPS-induced recruitment of NFkappaB-p65 to the kappaB enhancer (at -510) in the TNF-alpha gene. In the present study, we used EMSA and chromatin immunoprecipitation assays to further analyze the complex effects of FRT on the recruitment of transcription factors and co-activators on the TNF-alpha gene in LPS-stimulated RAW 264.7 mouse macrophages. Our results showed that in FRT-exposed RAW cells, HSF-1 was recruited only to the 5'-UTR site, and no additional interaction was evident in the TNF-alpha gene up to 1,300 nt upstream of the transcription start site. Similarly, FRT exposure selectively reduced LPS-induced NFkappaB-p65 recruitment to the kappaB enhancer site at -510 without affecting the other three kappaB enhancer sites present in the TNF-alpha 5'-flanking sequence. Finally, we found that FRT exposure abrogated LPS-stimulated recruitment of Sp1 to the proximal TNF-alpha promoter without any change in associated histone H3 acetylation around the TNF-alpha promoter and despite a marked increase in the total intra-nuclear Sp1 DNA binding activity. In conclusion, our studies further emphasize the complex and redundant control of TNF-alpha transcription and identify additional potential mechanisms through which FRT exposure may reduce TNF-alpha expression by selectively modifying gene-specific recruitment of transcription factors to the proximal TNF-alpha promoter.

Peroxisome proliferator-activated receptor {delta} regulates inflammation via NF-{kappa}B signaling in polymicrobial sepsis

The nuclear peroxisome proliferator-activated receptor δ (PPARδ) is an important regulator of lipid metabolism. In contrast to its known effects on energy homeostasis, its biological role on inflammation is not well understood. We investigated the role of PPARδ in the modulation of the nuclear factor-κB (NF-κB)-driven inflammatory response to polymicrobial sepsis in vivo and in macrophages in vitro. We demonstrated that administration of GW0742, a specific PPARδ ligand, provided beneficial effects to rats subjected to cecal ligation and puncture, as shown by reduced systemic release of pro-inflammatory cytokines and neutrophil infiltration in lung, liver, and cecum, when compared with vehicle treatment. Molecular analysis revealed that treatment with GW0742 reduced NF-κB binding to DNA in lung and liver. In parallel experiments, heterozygous PPARδ-deficient mice suffered exaggerated lethality when subjected to cecal ligation and puncture and exhibited severe lung injury and higher levels of circulating tumor necrosis factor-α (TNFα) and keratinocyte-derived chemokine than wild-type mice. Furthermore, in lipopolysaccharide-stimulated J774.A1 macrophages, GW0742 reduced TNFα production by inhibiting NF-κB activation. RNA silencing of PPARδ abrogated the inhibitory effects of GW0742 on TNFα production. Chromatin immunoprecipitation assays revealed that PPARδ displaced the NF-κB p65 subunit from the κB elements of the TNFα promoter, while recruiting the co-repressor BCL6. These data suggest that PPARδ is a crucial anti-inflammatory regulator, providing a basis for novel sepsis therapies.

Porcine reproductive and respiratory syndrome virus non-structural protein 1 suppresses tumor necrosis factor-alpha promoter activation by inhibiting NF-κB and Sp1

The objective of this study was to identify porcine reproductive and respiratory syndrome virus (PRRSV)-encoded proteins that are responsible for the inhibition of TNF-α expression and the mechanism(s) involved in this phenomenon. Using a TNF-α promoter reporter system, the non-structural protein 1 (Nsp1) was found to strongly suppress the TNF-α promoter activity. Such inhibition takes place especially at the promoter's proximal region. Both Nsp1α and Nsp1β, the two proteolytic fragments of Nsp1, were shown to be involved in TNF-α promoter suppression. Furthermore, using reporter plasmids specific for transcription factors (TFs) that bind to TNF-α promoter, Nsp1α and Nsp1β were demonstrated to inhibit the activity of the TFs that bind CRE-κB(3) and Sp1 elements respectively. Subsequent analyses showed that Nsp1α moderately inhibits NF-κB activation and that Nsp1β completely abrogates the Sp1 transactivation. These findings reveal one of the important mechanisms underlying the innate immune evasion by PRRSV during infection.

In vitro effects of calcium fructoborate upon production of inflammatory mediators by LPS-stimulated RAW 264.7 macrophages

The present study is supported by our previous findings suggesting that calcium fructoborate (CF) has anti-inflammatory and antioxidant properties. Thus, we investigated the effects of CF on a model for studying inflammatory disorders in vitro represented by lipopolysaccharide (LPS)-stimulated murine macrophage RAW 264.7 cells. This investigation was performed by analyzing the levels of some mediators released during the inflammatory process: cytokines such as tumor necrosis factor-alpha (TNF-alpha), interleukins IL-1beta and IL-6 as well as cyclooxygenase-2 (COX-2), the main enzyme responsible for endotoxin/LPS-induced prostaglandin synthesis by macrophages. We also measured production of nitric oxide (NO) that plays an important role in the cytotoxicity activity of macrophages towards microbial pathogens. After CF treatment of LPS-stimulated macrophages we found an up-regulation of TNF-alpha protein level in culture medium, no significant changes in the level of COX-2 protein expression and a decrease in NO production as well as in IL-1beta and IL-6 release. Collectively, this series of experiments indicate that CF affect macrophage production of inflammatory mediators. However, further research is required in order to establish whether CF treatment can be beneficial in suppression of pro-inflammatory cytokine production and against progression of endotoxin-related diseases.

Ordered transcriptional factor recruitment and epigenetic regulation of tnf-alpha in necrotizing acute pancreatitis

Tauhe expression of the critical initiator cytokine TNF-alpha was strongly upregulated in vivo in acute necrotic pancreatitis (AP) in rodents and in vitro in TNF-alpha activated acinar AR42J cells. Upregulation of tnf-alpha, inos, icam-1 and il-6 occurred both in TNF-alpha receptor 1 and 2 knock-out mice, but not in TNF-alpha knock-out mice, in cerulein-induced acute pancreatitis. Chromatin immunoprecipitation analysis showed that transcriptional factors (ELK-1, SP1, NF-kappaB and EGR-1) and chromatin modification complexes (HDAC1, HDAC2, GCN5, PCAF and CBP) were recruited and/or released from the promoter in a strictly ordered mechanism. Activation of tnf-alpha gene was also accompanied by an ordered increased level of histone H3K9, H3K14 and H3K18-acetylation and H3K4 methylation, as well as H4K5 acetylation. A better knowledge of the molecular mechanisms that control tnf-alpha gene regulation will provide deeper understanding of the initiation and development of the inflammatory processes occurring in acute pancreatitis triggered by TNF-alpha cytokine.

Global transcriptional response of macrophage-like THP-1 cells to Shiga toxin type 1

Shiga toxins (Stxs) are bacterial cytotoxins produced by the enteric pathogens Shigella dysenteriae serotype 1 and some serotypes of Escherichia coli that cause bacillary dysentery and hemorrhagic colitis, respectively. To date, approaches to studying the capacity of Stxs to alter gene expression in intoxicated cells have been limited to individual genes. However, it is known that many of the signaling pathways activated by Stxs regulate the expression of multiple genes in mammalian cells. To expand the scope of analysis of gene expression and to better understand the underlying mechanisms for the various effects of Stxs on host cell functions, we carried out comparative microarray analyses to characterize the global transcriptional response of human macrophage-like THP-1 cells to Shiga toxin type 1 (Stx1) and lipopolysaccharides. The data were analyzed by using a rigorous combinatorial approach with three separate statistical algorithms. A total of 36 genes met the criteria of upregulated expression in response to Stx1 treatment, with 14 genes uniquely upregulated by Stx1. Microarray data were validated by real-time reverse transcriptase PCR for genes encoding early growth response 1 (Egr-1) (transcriptional regulator), cyclooxygenase 2 (COX-2; inflammation), and dual specificity phosphatase 1 (DUSP1), DUSP5, and DUSP10 (regulation of mitogen-activated protein kinase signaling). Stx1-mediated signaling through extracellular signal-regulated kinase 1/2 and Egr-1 appears to be involved in the increased expression and production of the proinflammatory mediator tumor necrosis factor alpha. Activation of COX-2 is associated with the increased production of proinflammatory and vasoactive eicosanoids. However, the capacity of Stx1 to increase the expression of genes encoding phosphatases suggests that mechanisms to dampen the macrophage proinflammatory response may be built into host response to the toxins.

Studies on the role of acid sphingomyelinase and ceramide in the regulation of tumor necrosis factor alpha (TNFalpha)-converting enzyme activity and TNFalpha secretion in macrophages

Acid sphingomyelinase (ASMase) has been proposed to mediate lipopolysaccharide (LPS) signaling in various cell types. This study shows that ASMase is a negative regulator of LPS-induced tumor necrosis factor alpha (TNFalpha) secretion in macrophages. ASMase-deficient (asm(-/-)) mice and isolated peritoneal macrophages produce severalfold more TNFalpha than their wild-type (asm(+/+)) counterparts when stimulated with LPS, whereas the addition of exogenous ceramides or sphingomyelinase reduces the differences. The underlying mechanism for these effects is not transcriptional but post-translational. The TNFalpha-converting enzyme (TACE) catalyzes the maturation of the 26-kDa precursor (pro-TNFalpha) to an active 17-kDa form (soluble (s)TNFalpha). In mouse peritoneal macrophages, the activity of TACE was the rate-limiting factor regulating TNFalpha production. A substantial portion of the translated pro-TNFalpha was not processed to sTNFalpha; instead, it was rapidly internalized and degraded in the lysosomes. TACE activity was 2-3-fold higher in asm(-/-) macrophages as compared with asm(+/+) macrophages and was suppressed when cells were treated with exogenous ceramide and sphingomyelinase. Indirect immunofluorescence analyses revealed distinct TNFalpha-positive structures in the close vicinity of the plasma membrane in asm(-/-) but not in asm(+/+) macrophages. asm(-/-) cells also had a higher number of early endosomal antigen 1-positive early endosomes. Experiments that involved inhibitors of TACE, endocytosis, and lysosomal proteolysis suggest that in the asm(-/-) cells a significant portion of pro-TNFalpha was sequestered within the early endosomes, and instead of undergoing lysosomal proteolysis, it was recycled to the plasma membrane and processed to sTNFalpha.

Transcriptional control of the TNF gene

The cytokine TNF is a critical mediator of immune and inflammatory responses. The TNF gene is an immediate early gene, rapidly transcribed in a variety of cell types following exposure to a broad range of pathogens and signals of inflammation and stress. Regulation of TNF gene expression at the transcriptional level is cell type- and stimulus-specific, involving the recruitment of distinct sets of transcription factors to a compact and modular promoter region. In this review, we describe our current understanding of the mechanisms through which TNF transcription is specifically activated by a variety of extracellular stimuli in multiple cell types, including T cells, B cells, macrophages, mast cells, dendritic cells, and fibroblasts. We discuss the role of nuclear factor of activated T cells and other transcription factors and coactivators in enhanceosome formation, as well as the contradictory evidence for a role for nuclear factor kappaB as a classical activator of the TNF gene. We describe the impact of evolutionarily conserved cis-regulatory DNA motifs in the TNF locus upon TNF gene transcription, in contrast to the neutral effect of single nucleotide polymorphisms. We also assess the regulatory role of chromatin organization, epigenetic modifications, and long-range chromosomal interactions at the TNF locus.

Reduced transcript stabilization restricts TNF-alpha expression in RAW264.7 macrophages infected with pathogenic mycobacteria: evidence for an involvement of lipomannan

Despite the critical role that TNF-alpha plays in the containment of mycobacterial infection, the mechanisms involved in regulation of its expression by mycobacteria are poorly defined. We addressed this question by studying MAP, which causes a chronic enteritis in ruminants and is linked to human Crohn's disease. We found that in MAP infected macrophages, TNF-alpha gene expression was substantially lower than in macrophages infected with nonpathogenic MS or stimulated with LPS. TNF-alpha transcriptional one could not fully explain the differential TNF-alpha mRNA expression, suggesting that there must be a substantial contribution by post-transcriptional mechanisms.Accordingly, we found reduced TNF-alpha mRNA stability in MAP-infected macrophages. Further comparison of MAP- and MS-infected macrophages revealed that lower TNF-alpha mRNA stability combined with lower mRNA and protein expression in MAP-infected macrophages correlated with lower p38 MAPK phosphorylation. These findings were independent of viability of MAP and MS. We demonstrate that the major mycobacterial cell-wall lipoglycan LM of MAP and MS induced TNF-alpha mRNA transcription,but only the MS-LM induced p38 MAPK-dependent transcript stabilization. Overall, our data suggest that pathogenic mycobacteria cause weak p38 and TNF-alpha mRNA stabilization as a result of their structural cell-wall components such as LM and thereby, restrict TNF-alpha expression in macrophages.

The neuropeptide calcitonin gene-related peptide causes repression of tumor necrosis factor-alpha transcription and suppression of ATF-2 promoter recruitment in Toll-like receptor-stimulated dendritic cells

Sensory nerves may dampen inflammatory processes through the release of the neuropeptide calcitonin gene-related peptide (CGRP). CGRP mediates immunosuppressive activities through up-regulation of interleukin-10 or, alternatively, through an interleukin-10-independent pathway that is associated with rapid induction of the transcriptional inducible cAMP early repressor (ICER). In this work, we further investigated the molecular mechanisms of immune modulation by CGRP. Using TLR2-stimulated dendritic cells, we show that inhibition of tumor necrosis factor-alpha production by CGRP is dependent on up-regulation of endogenous ICER. Dendritic cell expression of ICER was selectively induced by CGRP and elevation of cellular cAMP levels but not by numerous pro- and anti-inflammatory cytokines. Treatment of dendritic cells with CGRP did not interfere with the induction of Tnfa gene expression but caused premature repression of TLR2-induced transcriptional activity. ATF-2 was rapidly phosphorylated and recruited to the Tnfa promoter following ligation of TLR2. Concomitant administration of CGRP completely prevented binding of ATF-2 to the Tnfa promoter, whereas recruitment of ICER was markedly elevated. In contrast, CGRP did not influence TLR2-stimulated binding of NF-kappaB p65. Together, these results are consistent with a model suggesting that CGRP causes rapid up-regulation of ICER, which in turn competes with ATF-2 for binding to the Tnfa promoter, leading to repression of gene expression.

Comparative analyses of single-nucleotide polymorphisms in the TNF promoter region provide further validation for the vervet monkey model of obesity

Tumor necrosis factor is a cytokine that plays critical roles in inflammation, the innate immune response, and a variety of other physiologic and pathophysiologic processes. In addition, TNF has recently been shown to mediate an intersection of chronic, low-grade inflammation and concurrent metabolic dysregulation associated with obesity and its comorbidities. As part of an ongoing initiative to further characterize vervet monkeys originating from St Kitts as an animal model of obesity and inflammation, we sequenced and genotyped the human ortholog vervet TNF gene and approximately 1 kb of the flanking 3' and 5' regions from 265 monkeys in a closed, pedigreed colony. This process revealed a total of 11 single-nucleotide polymorphisms (SNPs) and a single 4-bp insertion-deletion, with minor allele frequencies of 0.08 to 0.39. Many of these polymorphisms were in strong or complete linkage disequilibrium with each other, and all but 1 were contained within a single haplotype block, comprising 5 haplotypes with frequencies of 0.075 to 0.298. Using sequences from humans, chimpanzees, vervets, baboons, and rhesus macaques, phylogenetic shadowing of the TNF promoter region revealed that vervet SNPs, like the SNPs in related species, were clustered nonrandomly and nonuniformly around conserved transcription factor binding sites. These data, combined with previously defined heritable phenotypes, permit future association analyses in this nonhuman primate model and have great potential to help dissect the genetic and nongenetic contributions to complex diseases like obesity. More broadly, the sequence data and comparative analyses reported herein facilitates study of the evolution of regulatory sequences of inflammatory and immune-related genes.

Characterization of an ETS transcription factor in the sea scallop Chlamys farreri

We have cloned and characterized a cDNA encoding a putative ETS transcription factor, designated Cf-ets. The Cf-ets encodes a 406 amino acid protein containing a conserved ETS domain and a Pointed domain. Phylogenetic analysis revealed that Cf-ets belongs to the ESE group of ETS transcription factor family. Real-time PCR analysis of Cf-ets expression in adult sea scallop tissues revealed that Cf-ets was expressed mainly in gill and hemocytes, in a constitutive manner. Cf-ets mRNA level in hemocytes increased drastically after microbial challenge indicated its indispensable role in the anti-infection process. Simultaneously, the circulating hemocyte number decreased. In mammals, most ETS transcription factors play indispensable roles in blood cell differentiation and linage commitment during hematopoisis. Cf-ets is therefore likely to be a potential biomarker for hematopoiesis studies in scallops.

Involvement of PU.1 in the transcriptional regulation of TNF-alpha

PU.1 is a myeloid- and lymphoid-specific transcription factor that serves many important roles in the development and specific gene regulation of hematopoietic lineages. Mast cells (MC) and dendritic cells (DC) express PU.1 at low and high levels, respectively. Previously, we found that enforced expression of PU.1 in MC resulted in acquisition of DC-like characteristics, including repression of several IgE-mediated responses due to reduced expression of IgE-signaling related molecules. In contrast, PU.1 overexpression in MC up-regulated TNF-alpha production in response to IgE- and LPS-stimulation suggesting that PU.1 positively regulates TNF-alpha expression. However, the role of PU.1 in the expression of TNF-alpha is largely unknown. In the present study, the effects of PU.1 on the TNF-alpha promoter in mouse bone marrow-derived (BM) MC and DC were studied. Real-time PCR, ELISA, and chromatin immunoprecipitation assays indicated that the kinetics and magnitude of TNF-alpha expression levels following LPS- or IgE-stimulation are related to the amount of PU.1 binding to the promoter. In brief, higher and delayed up-regulation of TNF-alpha promoter function was observed in DC, whereas there were lower and rapid responses in MC. When PU.1-overexpressing retrovirus vector was introduced into MC, the amount of PU.1 recruited to the TNF-alpha promoter markedly increased. The knockdown of PU.1 in BMDC by siRNA resulted in a reduction of TNF-alpha protein produced from LPS-stimulated BMDC. These observations indicate that PU.1 transactivates the TNF-alpha promoter and that the amount of PU.1 binding on the promoter is associated with promoter activity.

HIV-1 replication is differentially regulated by distinct clinical strains of Mycobacterium tuberculosis

Background

Tuberculosis (TB) is the largest cause of death in human immunodeficiency virus type 1 (HIV-1) infection, having claimed an estimated one third to one half of the 30 million AIDS deaths that have occurred worldwide. Different strains of Mycobacterium tuberculosis (MTb), the causative agent of TB, are known to modify the host immune response in a strain-specific manner. However, a MTb strain-specific impact upon the regulation of HIV-1 replication has not previously been established.

Methology/Principal Findings

We isolated normal human peripheral blood mononuclear cells (PBMC) and co-infected them with HIV-1 and with either the well characterized CDC1551 or HN878 MTb clinical isolate. We show that HIV-1 co-infection with the CDC1551 MTb strain results in higher levels of virus replication relative to co-infection with the HN878 MTb strain ex vivo. Furthermore, we show that the distinct pattern of CDC1551 or HN878 induced HIV-1 replication is associated with significantly increased levels of TNF and IL-6, and of the transcription and nuclear translocation of the p65 subunit of the transcription factor NF-κB, by CDC1551 relative to HN878.

Conclusions/Significance

These results provide a precedent for TB strain-specific effects upon HIV-1 replication and thus for TB strain-specific pathogenesis in the outcome of HIV-1/TB co-infection. MTb strain-specific factors and mechanisms involved in the regulation of HIV-1 during co-infection will be of importance in understanding the basic pathogenesis of HIV-1/TB co-infection.

Cytokine modulation of TLR expression and activation in mesenchymal stromal cells leads to a proinflammatory phenotype

Bone marrow-derived mesenchymal stromal cells (MSC) possess an immune plasticity manifested by either an immunosuppressive or, when activated with IFN-gamma, an APC phenotype. Herein, TLR expression by MSC and their immune regulatory role were investigated. We observed that human MSC and macrophages expressed TLR3 and TLR4 at comparable levels and TLR-mediated activation of MSC resulted in the production of inflammatory mediators such as IL-1beta, IL-6, IL-8/CXCL8, and CCL5. IFN-alpha or IFN-gamma priming up-regulated production of these inflammatory mediators and expression of IFNB, inducible NO synthase (iNOS), and TRAIL upon TLR activation in MSC and macrophages, but failed to induce IL-12 and TNF-alpha production in MSC. Nonetheless, TLR activation in MSC resulted in the formation of an inflammatory site attracting innate immune cells, as evaluated by human neutrophil chemotaxis assays and by the analysis of immune effectors retrieved from Matrigel-embedded MSC injected into mice after in vitro preactivation with cytokines and/or TLR ligands. Hence, TLR-activated MSC are capable of recruiting immune inflammatory cells. In addition, IFN priming combined with TLR activation may increase immune responses induced by Ag-presenting MSC through presentation of Ag in an inflammatory context, a mechanism that could be applied in a cell-based vaccine.

Shear stress-induced transcriptional regulation via hybrid promoters as a potential tool for promoting angiogenesis

Among the key effects of fluid shear stress on vascular endothelial cells is modulation of gene expression. Promoter sequences termed shear stress response elements (SSREs) mediate the responsiveness of endothelial genes to shear stress. While previous studies showed that shear stress responsiveness is mediated by a single SSRE, these endogenous promoters often encode for multiple SSREs. Moreover, hybrid promoters encoding a single SSRE rarely respond to shear stress at the same magnitude as the endogenous promoter. Thus, to better understand the interplay between the various SSREs, and between SSREs and endothelial-specific sequences (ESS), we generated a series of constructs regulated by SSREs cassettes alone, or in combination with ESS, and tested their response to shear stress and endothelial specific expression. Among these constructs, the most responsive promoter (NR1/2) encoded a combination of two GAGACC/SSREs, the Sp1/Egr1 sequence, as well as a TPA response element (TRE). This construct was four- to five-fold more responsive to shear stress than a promoter encoding a single SSRE. The expression of constructs containing other SSRE combinations was unaffected or suppressed by shear stress. Addition of ESS derived from the Tie2 promoter, either 5' or 3' to NR1/2 resulted in shear stress transcriptional suppression, yet retained endothelial specific expression. Thus, the combination and localization order of the various SSREs in a single promoter is crucial in determining the pattern and degree of shear stress responsiveness. These shear stress responsive cassettes may prove beneficial in our attempt to time the expression of an endothelial transgene in the vasculature.

Toxoplasma gondii prevents chromatin remodeling initiated by TLR-triggered macrophage activation

Macrophages infected with the opportunistic protozoan Toxoplasma gondii are unable to up-regulate many proinflammatory cytokine genes, including TNF (TNF-alpha), upon stimulation with LPS and other TLR ligands. In this study, we examined the influence of T. gondii on transcription factors associated with TNF-alpha transcription, as well as phosphorylation and acetylation of histone H3 at distal and proximal regions of the TNF-alpha promoter. During LPS stimulation, we found that Toxoplasma blocks nuclear accumulation of transcription factor c-Jun, but not that of cAMP response element-binding protein or NF-kappaB. However, chromatin immunoprecipitation studies revealed that binding of all of these transcription factors to the TNF promoter was decreased by T. gondii infection. Furthermore, the parasite blocked LPS-induced Ser(10) phosphorylation and Lys(9)/Lys(14) acetylation of histone H3 molecules associated with distal and proximal regions of the TNF-alpha promoter. Our results show that Toxoplasma inhibits TNF-alpha transcription by interfering with chromatin remodeling events required for transcriptional activation at the TNF promoter, revealing a new mechanism by which a eukaryotic pathogen incapacitates proinflammatory cytokine production during infection.

Induction of hepatitis by JNK-mediated expression of TNF-alpha

The c-Jun NH(2)-terminal kinase (JNK) signaling pathway has been implicated in the development of tumor necrosis factor (TNF)-dependent hepatitis. JNK may play a critical role in hepatocytes during TNF-stimulated cell death in vivo. To test this hypothesis, we examined the phenotype of mice with compound disruption of the Jnk1 and Jnk2 genes. Mice with loss of JNK1/2 expression in hepatocytes exhibited no defects in the development of hepatitis compared with control mice, whereas mice with loss of JNK1/2 in the hematopoietic compartment exhibited a profound defect in hepatitis that was associated with markedly reduced expression of TNF-alpha. These data indicate that JNK is required for TNF-alpha expression but not for TNF-alpha-stimulated death of hepatocytes. Indeed, TNF-alpha induced similar hepatic damage in both mice with hepatocyte-specific JNK1/2 deficiency and control mice. These observations confirm a role for JNK in the development of hepatitis but identify hematopoietic cells as the site of the essential function of JNK.

Terameprocol, a methylated derivative of nordihydroguaiaretic acid, inhibits production of prostaglandins and several key inflammatory cytokines and chemokines

BACKGROUND

Extracts of the creosote bush, Larrea tridentata, have been used for centuries by natives of western American and Mexican deserts to treat a variety of infectious diseases and inflammatory disorders. The beneficial activity of this plant has been linked to the compound nordihydroguaiaretic acid (NDGA) and its various substituted derivatives. Recently, tetra-O-methyl NDGA or terameprocol (TMP) has been shown to inhibit the growth of certain tumor-derived cell lines and is now in clinical trials for the treatment of human cancer. In this report, we ask whether TMP also displays anti-inflammatory activity. TMP was tested for its ability to inhibit the LPS-induced production of inflammatory lipids and cytokines in vitro. We also examined the effects of TMP on production of TNF-alpha in C57BL6/J mice following a sublethal challenge with LPS. Finally, we examined the molecular mechanisms underlying the effects we observed.

METHODS

RAW 264.7 cells and resident peritoneal macrophages from C57BL6/J mice, stimulated with 1 mug/ml LPS, were used in experiments designed to measure the effects of TMP on the production of prostaglandins, cytokines and chemokines. Prostaglandin production was determined by ELISA. Cytokine and chemokine production were determined by antibody array and ELISA.Western blots, q-RT-PCR, and enzyme assays were used to assess the effects of TMP on expression and activity of COX-2.q-RT-PCR was used to assess the effects of TMP on levels of cytokine and chemokine mRNA.C57BL6/J mice injected i.p. with LPS were used in experiments designed to measure the effects of TMP in vivo. Serum levels of TNF-alpha were determined by ELISA.

RESULTS

TMP strongly inhibited the production of prostaglandins from RAW 264.7 cells and normal peritoneal macrophages. This effect correlated with a TMP-dependent reduction in levels of COX-2 mRNA and protein, and inhibition of the enzymatic activity of COX-2.TMP inhibited, to varying degrees, the production of several cytokines, and chemokines from RAW 264.7 macrophages and normal peritoneal macrophages. Affected molecules included TNF-alpha and MCP-1. Levels of cytokine mRNA were affected similarly, suggesting that TMP is acting to prevent gene expression.TMP partially blocked the production of TNF-alpha and MCP-1 in vivo in the serum of C57BL6/J mice that were challenged i.p. with LPS.

CONCLUSION

TMP inhibited the LPS-induced production of lipid mediators and several key inflammatory cytokines and chemokines, both in vitro and in vivo, raising the possibility that TMP might be useful as a treatment for a variety of inflammatory disorders.

A dimer-specific function of the transcription factor NFATp

The transcription factor NFATp integrates multiple signal transduction pathways through coordinate binding with basic-region leucine zipper (bZIP) proteins and other transcription factors. The NFATp monomer, even in the absence of its activation domains, recruits bZIP proteins to canonical NFAT-bZIP composite DNA elements. By contrast, the NFATp dimer and its bZIP partner bind noncooperatively to the NFAT-bZIP element of the tumor necrosis factor (TNF) gene promoter. This observation raises the possibility that the function of the activation domains of NFATp is dimer-specific. Here, we determine the consensus DNA binding site of the NFATp dimer, describe monomer- and dimer-specific NFATp-DNA contact patterns, and demonstrate that NFATp dimerization and dimer-specific activation subdomains are required for transcriptional activation from the TNF NFAT-bZIP element. We also show that these NFATp subdomains interact with the coactivator CBP (CREB-binding protein), which is required for NFATp-dependent TNF gene transcription. Thus, the context-specific function of the activation domains of NFAT can be potentiated by DNA-directed dimerization.

Suppression of lipopolysaccharide-stimulated tumor necrosis factor-alpha production by adiponectin is mediated by transcriptional and post-transcriptional mechanisms

Adiponectin is an adipokine with potent anti-inflammatory properties. Treatment of macrophages with adiponectin results in a suppression of lipopolysaccharide (LPS)-stimulated cytokine production. Here we investigated the transcriptional and post-transcriptional mechanisms by which adiponectin suppresses LPS-stimulated tumor necrosis factor (TNF)-alpha production. Treatment of RAW 264.7 macrophages with LPS increased TNF-alpha promoter-driven luciferase activity (TNF-alpha promoter/Luc activity) by 20-fold over basal. After culture with 1 mug/ml globular adiponectin (gAcrp) for 18 h, TNF-alpha promoter/Luc activity was increased even in the absence of LPS; further challenge with LPS only increased TNF-alpha promoter/Luc activity by 1.4-fold. Treatment with gAcrp decreased LPS-stimulated ERK1/2 phosphorylation and IkappaB degradation and suppressed the ability of LPS to increase the DNA binding activity of Egr-1 and p65. gAcrp also suppressed LPS-mediated stabilization of TNF-alpha mRNA. In controls cells, the half-life of TNF-alpha mRNA was increased from approximately 30 min at base line to approximately 80 min in response to LPS. After treatment with gAcrp for 18 h, LPS failed to increase TNF-alpha mRNA stability. This gAcrp-mediated loss of stimulus-induced stabilization of TNF-alpha mRNA required the presence of the TNF-alpha 3'-untranslated region and was associated with an increase in expression and RNA binding activity of tristetraprolin, an mRNA-binding protein that destabilizes TNF-alpha mRNA. In summary, these data characterize the complex transcriptional and post-transcriptional effects of gAcrp on LPS-stimulated TNF-alpha expression in macrophages. gAcrp treatment profoundly suppressed the ability of LPS to increase TNF-alpha transcription and reduced the stimulus-induced stabilization of TNF-alpha mRNA in response to LPS.

iNOS in cardiac myocytes plays a critical role in death in a murine model of hypertrophy induced by calcineurin

Transgenic overexpression of calcineurin (CN/Tg) in mouse cardiac myocytes results in hypertrophy followed by dilation, dysfunction, and sudden death. Nitric oxide (NO) produced via inducible NO synthase (iNOS) has been implicated in cardiac injury. Since calcineurin regulates iNOS expression, and since phenotypes of mice overexpressing iNOS are similar to CN/Tg, we hypothesized that iNOS is pathogenically involved in cardiac phenotypes of CN/Tg mice. CN/Tg mice had increased serum and cardiac iNOS levels. When CN/Tg-iNOS−/− and CN/Tg mice were compared, some phenotypes were similar: extent of hypertrophy and fibrosis. However, CN/Tg-iNOS−/− mice had improved systolic performance ( P < 0.001) and less heart block ( P < 0.0001); larger sodium current density and lower serum TNF-α levels ( P < 0.03); and less apoptosis ( P < 0.01) resulting in improved survival ( P < 0.0003). To define tissue origins of iNOS production, chimeric lines were generated. Bone marrow (BM) from wild-type or iNOS−/− mice was transplanted into CN/Tg mice. iNOS deficiency restricted to BM-derived cells was not protective. Calcineurin activates the local production of NO by iNOS in cardiac myocytes, which significantly contributes to sudden death, heart block, left ventricular dilation, and impaired systolic performance in this murine model of cardiac hypertrophy induced by the overexpression of calcineurin.

Effects of levo- and dextrosimendan on NF-kappaB-mediated transcription, iNOS expression and NO production in response to inflammatory stimuli

BACKGROUND AND PURPOSE

Levosimendan is used in the treatment of decompensated heart failure. It increases the contractility of the myocardium by sensitizing troponin C to calcium. In addition, levosimendan has been reported to have beneficial effects in experimental models of septic shock. Because heart failure and sepsis have been associated with excessive nitric oxide (NO) production through inducible NOS (iNOS), we investigated the effects of the simendans on NO production and iNOS expression and on generation of pro-inflammatory cytokines.

EXPERIMENTAL APPROACH

Macrophages and fibroblasts were exposed to inflammatory stimuli to induce iNOS expression. Proteins were measured by western blot and mRNA expression was determined by quantitative RT-PCR. Promoter activity and nuclear factor-kappaB (NF-kappaB) and the gamma-activated site (GAS; binding site for signal transducer and activator of transcription 1; STAT1)-mediated transcription were investigated using luciferase reporter constructs. Cytokines tumour necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6) were measured by ELISA.

KEY RESULTS

Levosimendan and dextrosimendan decreased NO production in a dose-dependent manner in cells exposed to inflammatory stimuli. The simendans decreased iNOS protein and mRNA expression but did not affect iNOS mRNA decay. These compounds decreased iNOS promoter activity and inhibited NF-kappaB-mediated transcription but not that mediated by STAT1/GAS. The simendans reduced IL-6 production slightly but they had no effect on TNF-alpha synthesis.

CONCLUSIONS AND IMPLICATIONS

The simendans downregulated NF-kappaB-dependent transcription and decreased iNOS promoter activity, iNOS expression and NO production. These mechanisms may contribute to their beneficial clinical effects.

Chromatin profiling across the human tumour necrosis factor gene locus reveals a complex, cell type-specific landscape with novel regulatory elements

The TNF locus on chromosome 6p21 encodes a family of proteins with key roles in the immune response whose dysregulation leads to severe disease. Transcriptional regulation is important, with cell type and stimulus-specific enhancer complexes involving the proximal TNF promoter. We show how quantitative chromatin profiling across a 34 kb region spanning the TNF locus has allowed us to identify a number of novel DNase hypersensitive sites and characterize more distant regulatory elements. We demonstrate DNase hypersensitive sites corresponding to the lymphotoxin alpha (LTA) and tumour necrosis factor (TNF) promoter regions, a CpG island in exon 4 of lymphotoxin beta (LTB), the 3′ end of nuclear factor of kappa light polypeptide gene enhancer in B-cells inhibitor-like 1 (NFKBIL1) and 3.4 kb upstream of LTA. These sites co-localize to highly conserved DNA sequences and show evidence of cell type specificity when lymphoblastoid, Jurkat, U937, HeLa and HEK293T cell lines are analysed using Southern blotting. For Jurkat T cells, we define histone modifications across the locus. Peaks of acetylated histone H3 and H4, together with tri-methyl K4 of histone H3, correspond to hypersensitive sites, notably in exon 4 of LTB. We provide evidence of a functional role for an intergenic DNase I hypersensitive site distal to LTA in Jurkat cells based on reporter gene analysis, with evidence of recruitment of upstream stimulatory factors (USF) transcription factors.

Polarization of primary human monocytes by IFN-gamma induces chromatin changes and recruits RNA Pol II to the TNF-alpha promoter

Monocyte polarization by IFN-gamma or IL-4 drives a complex series of cellular responses leading to increased intracellular killing (IFN-gamma) or enhanced healing (IL-4) among other functional responses. We studied the effect of IL-4 and IFN-gamma polarization on histone modifications at the TNF-alpha locus in human primary monocytes. IFN-gamma polarization markedly increased the expression of TNF-alpha, whereas IL-4 treatment decreased the expression. We found that IFN-gamma alone increased histone H4 acetylation at the TNF-alpha promoter. The effect of IFN-gamma on TNF-alpha expression was durable upon cytokine washout and even repolarization with IL-4. Concordantly, IFN-gamma-mediated H4 acetylation was also durable. IFN-gamma recruited activating transcription factor-2 via p38 to the TNF-alpha promoter, but inhibition of p38 had minimal effect on H4 acetylation. In a novel finding, we found that IFN-gamma recruited RNA Pol II to the human TNF-alpha promoter via ERK signaling, but did so without initiating transcription, leading to a poised condition. These studies provide an important perspective on monocyte polarization. Polarization by IFN-gamma has a durable effect on TNF-alpha expression, and histone acetylation may provide a mechanism for persistence of the effect.

Alcohol and lipid metabolism

Many new mechanisms for alcoholic steatosis have been suggested by work reported in the last five years. These include alterations of transcriptional controls of lipid metabolism, better understanding of the effects of abnormal methionine metabolism on the endoplasmic reticulum stress response, unraveling of the basis for sensitization of the Kupffer cell to lipopolysaccharide, a better understanding of the role of cytokines and adipokines in alcoholic liver disease, and implication of the innate immune and complement systems in responses to alcohol. Much of this work has been facilitated by work with knockout mice. Undoubtedly, there are interrelationships among these various pathogenic mechanisms that ultimately will provide a more cohesive picture of how heavy alcohol use deranges hepatic lipid metabolism.

Genetic analysis of the role of the PI3K-Akt pathway in lipopolysaccharide-induced cytokine and tissue factor gene expression in monocytes/macrophages

LPS stimulation of monocytes/macrophages induces the expression of genes encoding proinflammatory cytokines and the procoagulant protein, tissue factor. Induction of these genes is mediated by various signaling pathways, including mitogen-activated protein kinases, and several transcription factors, including Egr-1, AP-1, ATF-2, and NF-kappaB. We used a genetic approach to determine the role of the phosphatidylinositol-3-kinase (PI3K)-protein kinase B (Akt) pathway in the regulation of LPS signaling and gene expression in isolated macrophages and in mice. The PI3K-Akt pathway is negatively regulated by the phosphatase and tensin homologue (PTEN). We used peritoneal exudate cells from Pik3r1-deficient mice, which lack the p85alpha regulatory subunit of PI3K and have reduced PI3K activity, and peritoneal macrophages from PTEN(flox/flox)/LysMCre mice (PTEN(-/-)), which have increased Akt activity. Analysis of LPS signaling in Pik3r1(-/-) and PTEN(-/-) cells indicated that the PI3K-Akt pathway inhibited activation of the ERK1/2, JNK1/2, and p38 mitogen-activated protein kinases and reduced the levels of nuclear Egr-1 protein and phosphorylated ATF-2. Modulating the PI3K-Akt pathway did not affect LPS-induced degradation of IkappaBalpha or NF-kappaB nuclear translocation. LPS induction of TNF-alpha, IL-6, and tissue factor gene expression was increased in Pik3r1(-/-) peritoneal exudate cells and decreased in PTEN(-/-) peritoneal macrophages compared with wild-type (WT) cells. Furthermore, LPS-induced inflammation and coagulation were enhanced in WT mice containing Pik3r1(-/-) bone marrow compared with WT mice containing WT bone marrow and in mice lacking the p85alpha subunit in all cells. Taken together, our results indicate that the PI3K-Akt pathway negatively regulates LPS signaling and gene expression in monocytes/macrophages.

Role of the cytomegalovirus major immediate early enhancer in acute infection and reactivation from latency

The cytomegalovirus (CMV) major immediate early (MIE) enhancer-containing promoter regulates the expression of the downstream MIE genes, which have critical roles in reactivation from latency and acute infection. The enhancer consists of binding sites for cellular transcription factors that are repeated multiple times. The primate and nonprimate CMV enhancers can substitute for one another. The enhancers are not functionally equivalent, but they do have overlapping activities. The CMV MIE enhancers are located between divergent promoters where the leftward genes are critical and essential for reactivation from latency and acute infection and the rightward gene is nonessential. The rightward transcription unit is controlled by an enhancer for murine CMV. In contrast, human CMV has a set of repressor elements that prevents enhancer effects on the rightward viral promoter. The human CMV enhancer that controls the leftward transcription unit has a distal component that is nonessential at high multiplicity of infection (MOI), but has a significant impact on the MIE gene expression at low MOI. The proximal enhancer influences directly the level of transcription of the MIE genes and contains an essential Sp-1 site. The MIE promoter has a site adjacent to the transcription start site that is essential at the earliest stage of infection. The MIE enhancer-containing promoter responds to signal transduction events and to cellular differentiation. The role of the CMV MIE enhancer-containing promoter in acute infection and reactivation from latency are reviewed.

Coactivator function of RIP140 for NFkappaB/RelA-dependent cytokine gene expression

Inflammatory responses represent a hallmark of numerous pathologies including sepsis, bacterial infection, insulin resistance, and malign obesity. Here we describe an unexpected coactivator function for the nuclear receptor interacting protein 140 (RIP140) for nuclear factor kappaB (NFkappaB), a master transcriptional regulator of inflammation in multiple tissues. Previous work has shown that RIP140 suppresses the expression of metabolic gene networks, but we have found that genetic as well as acute deficiency of RIP140 leads to the inhibition of the proinflammatory program in macrophages. The ability of RIP140 to function as a coactivator for cytokine gene promoter activity relies on direct protein-protein interactions with the NFkappaB subunit RelA and histone acetylase cAMP-responsive element binding protein (CREB)-binding protein (CBP). RIP140-dependent control of proinflammatory gene expression via RelA/CBP may, therefore, represent a molecular rational for the cellular integration of metabolic and inflammatory pathways.

Macrophage deletion of p38alpha partially impairs lipopolysaccharide-induced cellular activation

The activation of p38alpha, a MAPK family member, is associated with macrophage activation by microbial pattern molecules, such as LPS. The requirement of p38alpha in inflammatory responses has been shown in a number of studies using chemical inhibitors, though the inhibitors also inhibit p38beta and perhaps some other enzymes. In this study, we used conditional knockout of p38alpha in macrophages to address the role of p38alpha in macrophage activation. We found that p38alpha deficiency causes a significant inhibition in the production of LPS-induced TNF-alpha, IL-12, and IL-18, but it has little or no effect on IL-6 or IFN-beta production. Knockout of p38alpha in macrophages did not affect LPS-induced activation of the other major signaling pathways (NF-kappaB, Jnk, and Erk), nor did it affect the transcriptional activity of NF-kappaB. It had little inhibitory effect on LPS-induced AP-1 activity, but it significantly inhibited LPS-induced C/EBP-beta and CREB activation, indicating that the role of p38alpha in cytokine production in macrophages is at least in part through its regulation of C/EBP-beta and CREB activation. In addition, we also confirmed that p38alpha is important for phagocytosis of bacteria by macrophages. Our in vivo studies with two murine models showed that p38alpha is involved in sepsis. Collectively, our data demonstrate that p38alpha is an important player in inflammatory responses.

Polymorphisms of TNF-enhancer and gene for FcgammaRIIa correlate with the severity of falciparum malaria in the ethnically diverse Indian population

BACKGROUND

Susceptibility/resistance to Plasmodium falciparum malaria has been correlated with polymorphisms in more than 30 human genes with most association analyses having been carried out on patients from Africa and south-east Asia. The aim of this study was to examine the possible contribution of genetic variants in the TNF and FCGR2A genes in determining severity/resistance to P. falciparum malaria in Indian subjects.

METHODS

Allelic frequency distribution in populations across India was first determined by typing genetic variants of the TNF enhancer and the FCGR2A G/A SNP in 1871 individuals from 55 populations. Genotyping was carried out by DNA sequencing, single base extension (SNaPshot), and DNA mass array (Sequenom). Plasma TNF was determined by ELISA. Comparison of datasets was carried out by Kruskal-Wallis and Mann-Whitney tests. Haplotypes and LD plots were generated by PHASE and Haploview, respectively. Odds ratio (OR) for risk assessment was calculated using EpiInfotrade mark version 3.4.

RESULTS

A novel single nucleotide polymorphism (SNP) at position -76 was identified in the TNF enhancer along with other reported variants. Five TNF enhancer SNPs and the FCGR2A R131H (G/A) SNP were analyzed for association with severity of P. falciparum malaria in a malaria-endemic and a non-endemic region of India in a case-control study with ethnically-matched controls enrolled from both regions. TNF -1031C and -863A alleles as well as homozygotes for the TNF enhancer haplotype CACGG (-1031T>C, -863C>A, -857C>T, -308G>A, -238G>A) correlated with enhanced plasma TNF levels in both patients and controls. Significantly higher TNF levels were observed in patients with severe malaria. Minor alleles of -1031 and -863 SNPs were associated with increased susceptibility to severe malaria. The high-affinity IgG2 binding FcgammaRIIa AA (131H) genotype was significantly associated with protection from disease manifestation, with stronger association observed in the malaria non-endemic region. These results represent the first genetic analysis of the two immune regulatory molecules in the context of P. falciparum severity/resistance in the Indian population.

CONCLUSION

Association of specific TNF and FCGR2A SNPs with cytokine levels and disease severity/resistance was indicated in patients from areas with differential disease endemicity. The data emphasizes the need for addressing the contribution of human genetic factors in malaria in the context of disease epidemiology and population genetic substructure within India.

c-Jun amino terminal kinase 1 deficient mice are protected from streptozotocin-induced islet injury

In vitro studies have implicated the c-Jun amino terminal kinase (JNK) in cytokine-induced pancreatic injury leading to a loss of insulin production and hyperglycemia. We examined the role of JNK1 in the multiple low dose streptozotocin (MLD-STZ) model in which islet injury and hyperglycemia are dependent upon T cell immunity and pro-inflammatory cytokines. MLD-STZ in wild type mice induced islet leukocyte infiltration, cytokine production, beta-cell apoptosis, and hyperglycemia. In contrast, Jnk1-/- mice were substantially protected from a loss of insulin producing cells and hyperglycemia in the MLD-STZ model despite a marked islet T cell and macrophage infiltrate. Based upon several lines of evidence, this protection was attributed to a reduction in TNF-alpha production by infiltrating Jnk1-/- macrophages leading to reduced beta-cell apoptosis. In conclusion, JNK1 signaling plays an essential role in macrophage induced beta-cell apoptosis and the development of hyperglycemia in MLD-STZ induced pancreatic injury.

Prostaglandin E2 inhibits tumor necrosis factor-alpha RNA through PKA type I

Tumor necrosis factor-alpha (TNF-alpha) is a cytokine that may contribute to the pathogenesis of septic shock, rheumatoid arthritis, cancer, and diabetes. Prostaglandins endogenously produced by macrophages act in an autocrine fashion to limit TNF-alpha production. We investigated the timing and signaling pathway of prostaglandin-mediated inhibition of TNF-alpha production in Raw 264.7 and J774 macrophages. TNF-alpha mRNA levels were rapidly modulated by PGE(2) or carbaprostacylin. PGE(2) or carbaprostacyclin prevented and rapidly terminated on-going TNF-alpha gene transcription within 15 min of prostaglandin treatment. Selective activation of PKA type I, but not PKA type II or Epac, with chemical analogs of cAMP was sufficient to inhibit LPS-induced TNF-alpha mRNA levels. The mechanisms by which prostaglandins limit TNF-alpha mRNA levels may underlie endogenous regulatory mechanisms that limit inflammation, and may have important implications for understanding chronic inflammatory disease pathogenesis.