Signal transduction through NF-kappa B

Acetylation of nuclear factor-kappaB in rat amygdala improves long-term but not short-term retention of fear memory

Memory consolidation is mediated by new protein synthesis. However, the transcriptional pathways induced in neurons by behavioral training that activate gene responses have yet to be fully delineated. We have previously shown that nuclear factor kappaB (NF-kappaB) is activated in the amygdala after fear conditioning. Here we report that fear conditioning resulted in an increase in histone acetyl-transferase activity, the association between NF-kappaB p65 and CBP, and the increase in acetylated p65. Pretreating animals with histone deacetylase (HDAC) inhibitors prolonged the nuclear expression of acetyl-p65 and increased its DNA binding activity. Consistent with these results, HDAC inhibitors enhanced long-term but not short-term fear memory, and this effect was attenuated by kappaB decoy DNA, whereas scrambled DNA was without effect. This study provides evidence that HDAC-mediated deacetylation functions as an intranuclear molecular switch culminating in the termination of NF-kappaB transcriptional response that is involved in the formation of fear memory.

Brusatol-induced HL-60 cell differentiation involves NF-kappaB activation

Brusatol, a quassinoid isolated from the fruit of Brucea javanica, induces cell differentiation with various leukemic cell lines in the concentration range of 5-25 ng/ml. To investigate its mechanism of action, cultured HL-60 cells were treated with brusatol (25 ng/ml) for various periods of time and qualitatively analyzed for differential gene expression using a cDNA macroarray. As suggested by these preliminary data, we investigated the effect of brusatol on the Rel/nuclear factor-kappa B (NF-kappaB) family members and their role in HL-60 cell differentiation. When cells were treated with brusatol (25 ng/ml), p100/p52, p105/p50 and p65 mRNA were found to be up-regulated with a maximum after 8 h. As determined by electrophoretic mobility shift assays (EMSA), NF-kappaB was activated, involving p50 and p65. Moreover, immunoblots showed a decrease of IkappaBalpha and generation of the phosphorylated form of IkappaBalpha in whole cell lysates. Cell differentiation induced by brusatol was inhibited by SN50, a NF-kappaB translocation inhibitor. These results strongly suggest that brusatol induces activation of NF-kappaB and the activation and translocation of NF-kappaB into the nucleus is responsible for promoting HL-60 cell differentiation.

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Administration of antisense oligodeoxyribonucleotides targeting NF-kappaB prolongs allograft survival via suppression of cytotoxicity

Presentation of alloantigens by antigen-presenting cells (APC) deficient in expression of costimulatory molecules (CM) induces alloantigen-specific hyporesponsiveness or tolerance. NF-kappaB has been shown to be a crucial transcription factor that regulates CM expression on the surface of APC. We designed an antisense phosphorothioate oligodeoxynucleotide (ODN) to specifically inhibit mRNA of mouse NF-kappaB, resulting in a deficiency in CM expression on APC that may prolong organ allograft survival. Anti-NF-kappaB ODN was delivered systemically by an osmotic pump implanted in the abdominal cavity of recipients following transplantation of vascularized heart allografts. The animals in control groups were given scrambled control ODN or were left untreated. Normal C3H (H2(k)) recipients rejected B10 (H2(b)) heart allografts at a median survival time (MST) of 15 days. A 14-day administration of 12.5 mg/kg/day anti-NF-kappaB ODN prolonged the survival of cardiac allografts to an MST of 25 days (P <0.05). In contrast, a scrambled control ODN was not effective (MST 17 days, P >0.05 compared to untreated controls). To investigate the underlying mechanisms of the immunosuppressive effect of anti-NF-kappaB ODN administration, graft infiltrating cells, spleen cells, and serum were collected from animals on day 7 posttransplant. Freshly isolated graft-infiltrating cells from anti-NF-kappaB ODN-treated recipients exhibited significantly decreased donor-specific CTL activity. Generation of CTL activity of spleen T cells from anti-NF-kappaB ODN-treated recipients was also impaired compared with untreated animals. Administration of anti-NF-kappaB ODN did not influence the titers of complement-dependent cytotoxic antibodies. These data suggest that treatment with anti-NF-kappaB ODN markedly inhibits the cellular response of allograft recipients, resulting in significant prolongation of allograft survival. Antisense ODN therapy targeting NF-kappacB may be a novel strategy for future immunosuppressive therapy.

Generation of stably transfected Mammalian cell lines as fluorescent screening assay for NF-kappaB activation-dependent gene expression

Cellular stress protection responses lead to increased transcription of several genes via modulation of transcription factors. Activation of the Nuclear Factor kappaB (NF-kappaB) pathway as a possible antiapoptotic route represents one important cellular stress response. To identify conditions that are capable of modifying this pathway, a screening assay for detection of NF-kappaB-dependent gene activation using the reporter protein Enhanced Green Fluorescent Protein (EGFP) and its destabilized variant (d2EGFP) was developed. Human Embryonic Kidney (HEK/293) cells were stably transfected with a vector carrying EGFP or d2EGFP under control of a synthetic promoter containing 4 copies of the NF-kappaB response element. Treatment with tumor necrosis factor alpha (TNF-alpha) gave rise to substantial EGFP/d2EGFP expression in up to 90% of the cells and was therefore used to screen different stably transfected clones for induction of NF-kappaB-dependent gene expression. The time course of NF-kappaB activation leading to d2EGFP expression was measured in an oligonucleotide-based NF-kappaB-ELISA. NF-kappaB binding in-creased after 15-min incubation with TNF-alpha. In parallel, d2EGFP increased after 3 h and reached its maximum at 24 h. These results show (1) the time lag between NF-kappaB activation and d2EGFP transcription, translation, and protein folding and (2) the increased reporter gene expression after treatment with TNF-alpha to be caused by the activation of NF-kappaB. The detection of d2EGFP expression required FACS analysis or fluorescence microscopy, while EGFP could also be measured in the microplate reader, rendering the assay useful for high-throughput screening.

Aberrant Toll Receptor Expression and Endotoxin Hypersensitivity in Mice Lacking a Functional TGF-β1 Signaling Pathway

TGF-beta1 plays a central role in maintaining normal immune function and deficiency of this potent immunosuppressive molecule is linked to uncontrolled inflammation, cachexia, and multiorgan failure as seen in the TGF-beta1 null mouse. Infiltration of inflammatory cells into vital organs of the null mouse is accompanied by increased gene expression of inflammatory cytokines, including TNF-alpha and IL-1beta, as well as inducible NO synthase, each regulated by NF-kappaB. Treatment with the proteasome inhibitor MG132 to prevent NF-kappaB activation dramatically reduced NO production and expression of inflammatory cytokines. This inflammatory phenotype with NF-kappaB activation in the TGF-beta1 null mouse, in the absence of any identifiable pathogen, suggested activation of innate immune responses. Because Toll-like receptors (TLR) are essential in the activation of innate immunity, we examined inflamed tissue from TGF-beta1 null and wild-type mice for expression of TLR4, the receptor that interacts with bacterial cell wall LPS to initiate an NF-kappaB-dependent signaling pathway, leading to gene transcription of inflammatory mediators. Increased TLR4 mRNA expression observed in TGF-beta1 null mice as well as in mice lacking the TGF-beta transcription factor Smad3 was associated with LPS hyperresponsiveness leading to increased expression of inflammatory cytokines and NO and endotoxemia. Furthermore, mice lacking both TGF-beta1 and a functional TLR4 were resistant to endotoxin shock. Constitutive and/or environmental activation of TLR4 and downstream elements, in the absence of TGF-beta suppression, may impact on innate and adaptive immunity and contribute to massive uncontrolled inflammation.

Selenium attenuates lipopolysaccharide-induced oxidative stress responses through modulation of p38 MAPK and NF-kappaB signaling pathways

Lipopolysaccharide (LPS) produces reactive oxygen species (ROS) and nitric oxide (NO) in macrophages. These molecules are involved in inflammation associated with endotoxic shock. Selenium (Se), a biologically essential trace element, modulates the functions of many regulatory proteins involved in signal transduction and affects a variety of cellular activities, including cell growth and survival. We demonstrate that Se attenuated LPS-induced ROS and NO production in murine macrophage cultures in vitro. This Se-decreased production of NO was demonstrated by decreases in both mRNA and protein expression for inducible NO synthase (iNOS). The preventive effects of Se on iNOS were p38 mitogen-activated protein kinase- and nuclear factor-kappaB-dependent. Se specifically blocked the LPS-induced activation of p38 but not that of c-jun-N-terminal kinase and extracellular signal-regulated kinase; the p38-specific pathway was confirmed using p38 inhibitor SB 203580. These results suggest that the mechanism by which Se may act as an anti-inflammatory agent and that Se may be considered as a possible preventive intervention for endotoxemia, particularly in Se-deficient locations. However, the efficacy and safety of Se need to be further investigated, because long-term intake > 0.4 mg Se/day in adults can produce adverse effects.

Targeting melanocortin receptors as a novel strategy to control inflammation

Adrenocorticotropic hormone and alpha-, beta-, and gamma-melanocyte-stimulating hormones, collectively called melanocortin peptides, exert multiple effects upon the host. These effects range from modulation of fever and inflammation to control of food intake, autonomic functions, and exocrine secretions. Recognition and cloning of five melanocortin receptors (MCRs) has greatly improved understanding of peptide-target cell interactions. Preclinical investigations indicate that activation of certain MCR subtypes, primarily MC1R and MC3R, could be a novel strategy to control inflammatory disorders. As a consequence of reduced translocation of the nuclear factor kappaB to the nucleus, MCR activation causes a collective reduction of the major molecules involved in the inflammatory process. Therefore, anti-inflammatory influences are broad and are not restricted to a specific mediator. Short half-life and lack of selectivity could be an obstacle to the use of the natural melanocortins. However, design and synthesis of new MCR ligands with selective chemical properties are already in progress. This review examines how marshaling MCR could control inflammation.

Acute induction of inflammatory cytokine expression after gamma-irradiation in the rat: effect of an NF-kappaB inhibitor

PURPOSE

The pathologic changes within the intestinal muscle layer may be at the origin of the cytokines that account for acute radiation-induced inflammation. We were specifically interested in evaluating the efficacy of an inhibitor of nuclear transcription factor kappa B (NF-kappaB) activation that is involved in regulating cytokine expression.

METHODS AND MATERIALS

Cytokine expression was analyzed in the ileal muscularis layer by reverse transcriptase-polymerase chain reaction (RT-PCR) at 3 h, 6 h, and 3 days after a 10-Gy gamma whole-body irradiation of rats. Caffeic acid phenethyl ester (CAPE) was injected intraperitoneally (30 mg/kg) 15 min before irradiation and once a day for 3 days.

RESULTS

Interleukin (IL)-1beta, tumor necrosis factor alpha (TNF-alpha), and IL-6 mRNA increased at 3 h and 6 h after irradiation, and expression of IL-6 and IL-8 was elevated at 3 days. On the other hand, levels of the anti-inflammatory cytokine IL-10 were markedly lower on Day 3. Overexpression of IL-6 on Day 3 was combined with upregulation of the IL-6 receptors (gp130/gp80) and suppressor of cytokine signaling-3 (SOCS3) genes. CAPE treatment did not significantly change IL-1beta or TNF-alpha expressions in the irradiated rats; it increased IL-10 expression at 6 h but had no effect on it on Day 3. CAPE treatment inhibited the radiation-induced expression of IL-6, IL-6 receptors (IL-6rs), and SOCS3 at 3 days.

CONCLUSION

In vivo, irradiation induced a cascade of inflammatory responses that involved the transcription factor NF-kappaB; this inflammation was reduced by CAPE treatment.

Levetiracetam protects against kainic acid-induced toxicity

We investigated the Levetiracetam (LVT) ability to protect the brain against kainic acid (KA) induced neurotoxicity. Brain injury was induced by intraperitoneal administration of KA (10 mg/kg). Sham brain injury rats were used as controls. Animals were randomized to receive either LVT (50 mg/kg) or its vehicle (1 ml/kg) 30 min. before KA administration. Animals were sacrificed 6 hours after KA injection to measure brain malonildialdehyde (MDA), glutathione levels (GSH) and the mRNA for interleukin-1beta (IL-1beta) in the cortex and in the diencephalon. Behavioral changes were also monitored. Intraperitoneal administration of LVT decreased significantly MDA in the cortex (KA + vehicle = 0.25 +/- 0.03 nmol/mg protein; KA + LVT = 0.13 +/- 0.01 nmol/mg protein; P < 0.005), and in the diencephalons (KA + vehicle = 1,01 +/- 0.2 nmol/mg protein; KA + LVT = 0,33 +/- 0,08 nmol/mg protein; P < 0.005), prevented the brain loss of GSH in both cortex (KA + vehicle = 5 +/- 1 micromol/g protein; KA + LVT = 15 +/- 2 micromol/g protein; P < 0.005) and diencephalons (KA + vehicle = 9 +/- 0.8 micromol/g protein; KA + LVT = 13 +/- 0.3 micromol/g protein; P < 0.05), reduced brain IL-1beta mRNA and markedly controlled seizures. Histological analysis showed a reduction of cell damage in LVT treated samples. The present data indicate that LVT displays neuro-protective effects against KA induced brain toxicity and suggest that these effects are mediated, at least in part, by inhibition of lipid peroxidation.

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Effect of moxifloxacin on production of proinflammatory cytokines from human peripheral blood mononuclear cells

The effects of moxifloxacin, a new methoxyfluoroquinolone, on the production of proinflammatory cytokines from human peripheral blood mononuclear cells (PBMCs) were evaluated. Moxifloxacin inhibited the production of tumor necrosis factor alpha (TNF-alpha) and/or interleukin-6 (IL-6) by PBMCs stimulated with lipopolysaccharide (LPS), lipoteichoic acid (LTA), and heat-killed bacteria in a concentration-dependent manner without cytotoxic effects. The addition of moxifloxacin reduced the population of cells positive for CD-14 and TNF-alpha and for CD-14 and IL-6 among the LPS- or LTA-stimulated PBMCs. By Western blot analysis, moxifloxacin pretreatment reduced the degradation of IkappaBalpha in LPS-stimulated PBMCs. In conclusion, moxifloxacin could interfere with NF-kappaB activation by inhibiting the degradation of IkappaBalpha and reduce the levels of production of proinflammatory cytokines.

Gene expression changes associated with the endoplasmic reticulum stress response induced by microsomal cytochrome p450 overproduction

Induction of drug-metabolizing microsomal cytochromes p450 (p450s) results in a striking proliferation of the smooth endoplasmic reticulum (ER). Overexpression of P450s in yeast and cultured cells produces a similar response. The signals mediating this process are not known but probably involve signal transduction pathways involved in the unfolded protein response (UPR) or the ER overload response (EOR). We have examined the temporal response of specific genes in these pathways and genes globally to overexpression of p450 in cultured cells. Activity of NFkappaB, an EOR component, was substantially increased by overexpression of full-length p450 2C2 or a chimera with the 28-amino acid signal anchor sequence of p450 2C2 in HepG2 cells, and the activation correlated temporally with the accumulation of p450 in the cells. In the UPR pathway, activation of the transcription factor XBP1 by IRE1 also correlated with the accumulation of p450 in the cells, and in contrast, maximum activation of the BiP/grp78 promoter preceded the accumulation. Differential effects of expression of p450 on apoptosis were observed in nonhepatic COS1 and hepatic HepG2 cells. In COS1 cells, apoptosis was induced, and this correlated with sustained activation of the pro-apoptotic JNK pathway, induction of CHOP, and an absence of the increased NFkappaB activity. In HepG2 cells, JNK was only transiently activated, and CHOP expression was not induced. As assessed by DNA microarray analysis, up-regulation of signaling genes was predominant including those involved in anti-apoptosis and ER stress. These results suggest that both the EOR and UPR pathways are involved in the cellular response to induction of p450 expression and that in hepatic cells genes are also induced to block apoptosis, which may be a physiologically relevant response to prevent cell death during xenobiotic induced expression of p450 in the liver.

Immunosuppressory activity of ubiquitin fragments containing retro-RGD sequence

A peptide fragment corresponding to the ubiquitin(50-59) sequence (LEDGRTLSDY) (U50-59) possesses a very high immunosuppressory activity, comparable to that of cyclosporine, both in the cellular and humoral immune responses. We found that the pentapeptide DGRTL (U52-56) is the shortest, effective immunosuppressory fragment of ubiquitin, although its potency is weaker than that of U50-59. Replacement of each consecutive residue with alanine in U52-56 allowed identification of essential amino acids involved in the immunosuppression. We also evaluated the roles of its N- and C-terminal groups by their acetylation and/or amidation, respectively. The active sequence is located in the external loop of the molecule and therefore it may serve as an important functional epitope for intermolecular binding. Based on the crystal structure of ubiquitin molecule, we designed and synthesized the cyclic analogue with a restricted conformation, cyclo(Glt-Gln-Leu-Glu-Asp-Gly-Arg-Thr-Leu-Ser-Asp-Lys)-NH2 (Glt = glutaryl) by reacting the C-terminal Lys side chain with the glutarylated N-terminus. The peptide was designed to mimic the ubiquitin(48-59) loop, in order to obtain the ligand that may interact with hypothetical receptors of the loop. The cyclization product selectively but strongly suppresses the cellular immune response. The results indicate that the 48-59 loop may serve as an important functional epitope in the ubiquitin molecule for intermolecular binding.

The potential role of allergen-specific sublingual immunotherapy in atopic dermatitis

Atopic dermatitis is a chronic inflammatory skin disease associated with increasing prevalence, morbidity, and cost in developed Western countries. Frequently associated with respiratory allergy during adulthood, atopic dermatitis often represents the first phenotypic appearance of atopy in early childhood when the allergic 'march' starts and progressively moves toward food allergy, asthma, and rhinitis. At present, a consistent body of evidence supports the view that atopic dermatitis may represent the skin compartmentalization of a systemic allergic inflammation. Lymphocytes infiltrating early lesional skin express a T helper (Th) 2 pattern of cytokine secretion (increased levels of interleukin [IL]-4 and/or IL-13 and decreased levels of interferon-gamma) as well as the typical Th2-type chemokine receptor CCR4, specific to the thymus and activation-regulated chemokines. Keratinocytes from patients with atopic dermatitis produce thymic stromal lymphopoietin, a novel cytokine that supports the early lymphocyte development in mouse models, and activates dendritic cells involved in the pathogenesis of allergic diseases in humans. Increased levels of circulating hemopoietic precursor cells have been reported in atopic dermatitis, as in allergic asthma and rhinitis. Furthermore, the recognition of CD34+ hemopoietic precursor cells, and evidence for cellular differentiation/maturational events occurring within atopic dermatitis skin lesion infiltrates, are consistent with the recent reinterpretation of the Th2/Th1 paradigm, where Th2 cells appear to belong to the early stages and Th1 to the ultimate stages of a linear, rather than divergent, pattern of lymphoid differentiation. This more detailed understanding of the immunologic derangements contributing to the atopic dermatitis pathogenesis has led to growing interest in allergen-specific immunotherapy for the disease. Due to the complexity intrinsic to atopic dermatitis and the lack of consensus-based guidelines for standardized outcome measure, only eight studies are available in the literature for a qualitative evaluation of this treatment approach. Two of these studies were double blind and placebo controlled, and six were cohort studies. Immunotherapy was found to be effective in one controlled study and five observational reports. Uncertain results were provided by one low-powered, controlled study, and negative outcomes were raised by a unique study performed with oral immunotherapy, which is not an effective route of mucosal allergen administration. Thus, more efficacy studies are required before immunotherapy could be recommended for the routine treatment of atopic dermatitis. Allergen-specific sublingual immunotherapy, given its excellent safety profile and ability to interfere with the systemic aspects of allergic inflammation, appears a good potential candidate for the pathogenetic treatment of the disease.

Commensal anaerobic gut bacteria attenuate inflammation by regulating nuclear-cytoplasmic shuttling of PPAR-gamma and RelA

The human gut microflora is important in regulating host inflammatory responses and in maintaining immune homeostasis. The cellular and molecular bases of these actions are unknown. Here we describe a unique anti-inflammatory mechanism, activated by nonpathogenic bacteria, that selectively antagonizes transcription factor NF-kappaB. Bacteroides thetaiotaomicron targets transcriptionally active NF-kappaB subunit RelA, enhancing its nuclear export through a mechanism independent of nuclear export receptor Crm-1. Peroxisome proliferator activated receptor-gamma (PPAR-gamma), in complex with nuclear RelA, also undergoes nucleocytoplasmic redistribution in response to B. thetaiotaomicron. A decrease in PPAR-gamma abolishes both the nuclear export of RelA and the anti-inflammatory activity of B. thetaiotaomicron. This PPAR-gamma-dependent anti-inflammatory mechanism defines new cellular targets for therapeutic drug design and interventions for the treatment of chronic inflammation.

Unresponsiveness to surface antigen 1 modifies cytokine profiles in acute Toxoplasma gondii infection

Resistance to Toxoplasma gondii involves the development of a highly polarized Th1-type cytokine expression. SAG1 transgenic mice are highly susceptible to T. gondii infection due to their non-reactivity to SAG1 of the protozoan parasite. Here we describe cytokine profiles during the acute phase of T. gondii infection, which are associated with the susceptibility of SAG1 transgenic mice. SAG1 transgenic mice showed a 4.5-fold increase in susceptibility upon inoculation with a sublethal dose of the Beverley strain of T. gondii compared to their wild-type counterparts (mortality: 81 vs. 18%, respectively). When analysis of the most important cytokines involved in the mediation of resistance to infection was carried out, SAG1 transgenic mice exhibited low production levels of IL-12, IFN-gamma and TNF-alpha in sera during the acute phase of T. gondii infection. Antibody and T cells specific for SAG1 were not mounted upon SAG1 stimulation in SAG1 transgenic mice. Moreover, in vitro studies indicated that in SAG1 transgenic mice IFN-gamma and IL-12 production was lower than in their wild-type counterparts, although levels of TNF-alpha increased in SAG1 transgenic mice on day 9 after infection. Low IgG2a levels were detected in SAG1 transgenic mouse sera. Unresponsiveness to SAG1 of T. gondii renders SAG1 transgenic mice unable to develop a strong Th1-based protection against T. gondii infection. These results provide evidence that SAG1 is a pivotal antigen involved in the induction of immune responses towards the development of Th1-protective immunity during T. gondii infection.

Regulation of ascidian Rel by its alternative splice variant

The Rel/NF-kappaB family of transcription factors play key roles in morphogenesis and immune responses. We reported previously that As-rel1 and As-rel2 of the ascidian Halocynthia roretzi are involved in notochord formation. The As-rel1 protein is a typical Rel/NF-kappaB family member, whereas the As-rel2 protein is a novel truncated product of As-rel1 that lacks a nuclear localization signal and the unique C-terminal region. Here, we present conclusive evidence that As-rel1 and As-rel2 are generated from a single gene by alternative splicing. We analyzed the roles of As-rel2 using cells transfected with As-rel1 or As-rel2 or both. As-rel1 was localized in the nucleus and As-rel2 in the cytoplasm when they were transfected individually. In contrast, when they were transfected simultaneously, both were localized in the nucleus because of the association of As-rel2 with As-rel1. In this case, the transcriptional activity of As-rel1 was suppressed by As-rel2. Ascidian IkappaB was found to sequester As-rel1 in the cytoplasm and suppress its transcriptional activity when As-rel1 and IkappaB were transfected simultaneously. In contrast, when As-rel1 and IkappaB were transfected together with As-rel2, As-rel1 was transported into the nucleus and its transcriptional activity was rescued from inhibition by IkappaB, whereas As-rel2 remained localized in the cytoplasm, suggesting IkappaB sequestration in the cytoplasm by As-rel2. From these findings, we conclude that the alternative splice variant, As-rel2, regulates the nuclear localization and transcriptional activity of As-rel1.

Use of Microarray Analysis to Unveil Transcription Factor and Gene Networks Contributing to β Cell Dysfunction and Apoptosis

The beta cell fate following immune-mediated damage depends on an intricate pattern of dozens of genes up- or downregulated in parallel and/or sequentially. We are utilizing microarray analysis to clarify the pattern of gene expression in primary rat beta cells exposed to the proapoptotic cytokines, IL-1beta and/or IFN-gamma. The picture emerging from these experiments is that beta cells are not passive bystanders of their own destruction. On the contrary, beta cells respond to damage by activating diverse networks of transcription factors and genes that may either lead to apoptosis or preserve viability. Of note, cytokine-exposed beta cells produce and release chemokines that may contribute to the homing and activation of T cells and macrophages during insulitis. Several of the effects of cytokines depend on the activation of the transcription factor, NF-kappaB. NF-kappaB blocking prevents cytokine-induced beta cell death, and characterization of NF-kappaB-dependent genes by microarray analysis indicated that this transcription factor controls diverse networks of transcription factors and effector genes that are relevant for maintenance of beta cell differentiated status, cytosolic and ER calcium homeostasis, attraction of mononuclear cells, and apoptosis. Identification of this and additional "transcription factor networks" is being pursued by cluster analysis of gene expression in insulin-producing cells exposed to cytokines for different time periods. Identification of complex gene patterns poses a formidable challenge, but is now technically feasible. These accumulating evidences may finally unveil the molecular mechanisms regulating the beta cell "decision" to undergo or not apoptosis in early T1DM.

Distribution of NF-kappaB-binding sites across human chromosome 22

We have mapped the chromosomal binding site distribution of a transcription factor in human cells. The NF-kappaB family of transcription factors plays an essential role in regulating the induction of genes involved in several physiological processes, including apoptosis, immunity, and inflammation. The binding sites of the NF-kappaB family member p65 were determined by using chromatin immunoprecipitation and a genomic microarray of human chromosome 22 DNA. Sites of binding were observed along the entire chromosome in both coding and noncoding regions, with an enrichment at the 5' end of genes. Strikingly, a significant proportion of binding was seen in intronic regions, demonstrating that transcription factor binding is not restricted to promoter regions. NF-kappaB binding was also found at genes whose expression was regulated by tumor necrosis factor alpha, a known inducer of NF-kappaB-dependent gene expression, as well as adjacent to genes whose expression is not affected by tumor necrosis factor alpha. Many of these latter genes are either known to be activated by NF-kappaB under other conditions or are consistent with NF-kappaB's role in the immune and apoptotic responses. Our results suggest that binding is not restricted to promoter regions and that NF-kappaB binding occurs at a significant number of genes whose expression is not altered, thereby suggesting that binding alone is not sufficient for gene activation.

Role of nuclear factor-kappa B in the regulation of intercellular adhesion molecule 1 after infection of human bronchial epithelial cells by Bordetella pertussis

Previous work has demonstrated that infection of human bronchial epithelial cells by Bordetella pertussis up-regulates intercellular adhesion molecule-1 (ICAM-1) gene and protein expression. It has also been shown that interaction of the Arg-Gly-Asp (RGD) site of filamentous hemagglutinin (FHA) with host cell very late antigen (VLA)-5 (alpha 5 beta 1 integrin) is required for the up-regulation of epithelial ICAM-1 expression, and that pertussis toxin (PT) impairs this response. We therefore examined the molecular mechanisms leading to B. pertussis-induced ICAM-1 up-regulation in BEAS-2B human bronchial epithelial cells. A colorimetric nuclear factor kappa B (NF-kappa B) activation assay demonstrated that NF-kappa B was activated in response to infection of these cells with B. pertussis. This activation occurred in an FHA(RGD)-dependent manner, and was blocked by an antibody against VLA-5, implying that binding of the RGD to VLA-5 integrin is involved in NF-kappa B activation. Western blot analysis revealed that the activation of NF-kappa B by B. pertussis was preceded by degradation of I kappa B alpha, a major cytoplasmic inhibitor of NF-kappa B. Pretreatment of the BEAS-2B cells with the NF-kappa B inhibitors pyrrolidine dithiocarbamate (PDTC), MG-132, and SN50 resulted in a marked decrease in B. pertussis-induced ICAM-1 expression, implying the involvement of NF-kappa B in ICAM-1 expression. Purified PT abrogated both NF-kappa B activation and I kappa B alpha degradation. These results suggest that ligation of VLA-5 integrin by FHA induces RGD-dependent NF-kappa B activation, thus leading to the up-regulation of epithelial ICAM-1 expression, and that a PT-sensitive G protein may be involved in this signaling pathway.

A proteasome inhibitor reduces concurrent, sequential, and long-term IL-1 beta- and TNF-alpha-induced ECAM expression and adhesion

A promising approach for reducing aberrant leukocyte-endothelial adhesion during pathological inflammation is to inhibit endothelial cell adhesion molecule (ECAM) expression at the transcription level. Several compounds have been shown to decrease cytokine-induced upregulation of ECAMs primarily by modulating the activity of transcription factors [e.g., nuclear factor-kappa B (NF-kappa B)]. The majority of the in vitro studies have focused on the effect of transcription inhibitors on endothelial cells exposed to a single cytokine [primarily tumor necrosis factor-alpha (TNF-alpha)] for a relatively short period of time (primarily 4-6 h). However, in the in vivo setting, multiple cytokines [e.g., interleukin-1 beta (IL-1 beta) and TNF-alpha] may be present for extended periods of time. Thus we studied the effects of a transcription inhibitor, the proteasome inhibitor lactacystin, on ECAM expression and myeloid (HL60) cell adhesion to human umbilical vein endothelial cells (HUVEC) activated by concurrent, sequential, and long-term (24 h) treatment with IL-1 beta and TNF-alpha. We show, for the first time, that lactacystin inhibits 1) 4-h concurrent IL-1 beta- and TNF-alpha-induced expression of E-selectin, VCAM-1, ICAM-1, and HL60 cell adhesion to HUVEC; 2) 4-h TNF-alpha-induced expression of E-selectin, VCAM-1, and HL60 cell adhesion to HUVEC that have become desensitized to IL-1 beta activation; 3) 24-h TNF-alpha-induced expression of E-selectin and VCAM-1 but not ICAM-1; and 4) 24-h TNF-alpha-induced HL60 cell adhesion to HUVEC. Combined, our results demonstrate that a proteasome inhibitor can reduce concurrent, sequential, and long-term IL-1 beta- and TNF-alpha-induced ECAM expression and myeloid cell adhesion.

Inhibition of Helicobacter pylori-induced nuclear factor-kappa B activation and interleukin-8 gene expression by ecabet sodium in gastric epithelial cells

BACKGROUND

Helicobacter pylori stimulates nuclear factor-kappa B (NF-kappa B) activation and chemokine interleukin-8 (IL-8) expression in gastric epithelial cells. Ecabet sodium (ecabet), a locally acting antiulcer drug, is known to have anti-H. pylori activity. However, there is little understanding of how ecabet induces anti-inflammatory activity in gastric epithelial cells infected with H. pylori. The aim of this study was to investigate the effects of ecabet on IL-8 gene expression and NF-kappa B activation in human gastric epithelial cells infected with H. pylori.

MATERIALS AND METHODS

After Hs746T, MKN-45, or SNU-5 gastric epithelial cell lines had been infected with cagA+cytotoxin+H. pylori in the presence of ecabet, IL-8 mRNA expression was assessed by quantitative reverse transcription-polymerase chain reaction, and IL-8 secretion was measured by enzyme-linked immunosorbent assay. NF-kappa B and inhibitory kappa B-alpha (I kappa B alpha) signals were assayed by electrophoretic mobility shift assay and Western blot, respectively. The activation of NF-kappa B and IL-8 reporter genes was determined by luciferase assay.

RESULTS

Ecabet showed no antimicrobial activiy against Gram-positive or -negative bacteria. However, ecabet inhibited transcription of the IL-8 gene and secretion of IL-8 by gastric epithelial cells infected with H. pylori at a concentration of 5 micro g/ml. Moreover, ecabet inhibited the activation of NF- kappa B and the degradation of I kappa B alpha in gastric epithelial cells in response to H. pylori infection. In addition, the NF-kappa B signal inhibited by ecabet was comprised predominantly of heterodimers of p65/p50.

CONCLUSIONS

Ecabet inhibited H. pylori-induced IL-8 gene transcription and secretion by suppressing the NF-kappa B signal. This inhibition might be one pathway by which ecabet exerts its anti-inflammatory effect on H. pylori-induced gastric inflammation.

Renin-angiotensin system activation and interstitial inflammation in human diabetic nephropathy

BACKGROUND

The molecular mechanisms of renal injury in diabetic nephropathy (DN) are not completely understood, although inflammatory cells play a key role. The renin-angiotensin system (RAS) is involved in kidney damage; however, few studies have examined the localization of RAS components in human DN. Our aim was to investigate in renal biopsies the expression of RAS and their correlation with proinflammatory parameters and renal injury.

METHODS

The biopsies from 10 patients with type 2 diabetes mellitus and overt nephropathy were studied for the expression of RAS components by immunohistochemistry (IH). In addition, by Southwestern histochemistry we studied the in situ detection of the activated nuclear factor kappa B (NFkappaB), and by IH and/or in situ hybridization (ISH), the expression of monocyte chemoattractant protein-1 (MCP-1) and regulated upon activation, normal T cell expressed and secreted (RANTES), whose genes are regulated by NFkappaB.

RESULTS

Angiotensin-converting enzyme (ACE) immunostaining was elevated in tubular cells and appeared in interstitial cells. Elevated levels of angiotensin II (Ang II) immunostaining were observed in tubular and infiltrating interstitial cells. There was also a down-regulation of AT1 and up-regulation of AT2 receptors. An activation of NFkappaB and a marked up-regulation of NFkappaB-dependent chemokines mainly in tubular cells was observed. Elevated levels of NFkappaB, chemokines, and Ang II in tubules were correlated with proteinuria and interstitial cell infiltration.

CONCLUSIONS

Our results show that in human DN, RAS components are modified in renal compartments, showing elevated local Ang II production, activation of tubular cells, and induction of proinflammatory parameters. These data suggest that Ang II contributes to the renal inflammatory process, and may explain the molecular mechanisms of the beneficial effect of RAS blockade.

Endotoxin inhibitor blocks heat exposure-induced expression of brain cytokine mRNA in aged rats

To investigate the age-related changes in the expression of interleukin-1beta (IL-1beta) and its related substances in the brain during heat stress, we measured amounts of mRNAs for IL-1beta, cyclooxygenase-2 (COX-2), and an inhibitor of nuclear factor (NF)-kappaB-beta (IkappaB-beta) that is known to reflect an activation of NF-kappaB, in the cortex, cerebellum, and hippocampus using a quantitative real-time capillary PCR method. The basal levels of IL-1beta mRNA in aged rats (108-110 weeks old) was significantly higher than those in young animals (10-11 weeks old) in these brain regions. Heat exposure (33 degrees C) for 1 h enhanced the expression of IL-1beta and COX-2 mRNAs in aged rats but not in young ones. The amount of lipopolysaccharide (LPS) assessed by its bioactivity in the cortex increased by heat exposure only in aged rats. To further examine an involvement of LPS in the increase in mRNAs, an endotoxin inhibitor (EI), a synthetic peptide that detoxifies LPS by binding to the toxic component of LPS, lipid A, was intraperitoneally injected before heat exposure in aged rats. An intraperitoneal injection of EI significantly attenuated the heat exposure-induced increases in mRNAs for IL-1beta, COX-2, IkappaB-beta, and the LPS activity. Administration of EI also debilitated the heat exposure-induced hyperthermia and responses of plasma ACTH and catecholamines. These findings, taken together, suggest that the bacterial translocation is involved in the mechanisms of the responses to heat exposure in aged rats including the increased expression of mRNAs for IL-1beta and its related substances in the brain.

Tumor necrosis factor-alpha induces nuclear factor-kappaB-dependent TRPC1 expression in endothelial cells

We investigated the role of tumor necrosis factor-alpha (TNF-alpha) in activating the store-operated Ca2+ channels in endothelial cells via the expression of transient receptor potential channel (TRPC) isoforms. We observed that TNF-alpha exposure of human umbilical vein endothelial cells resulted in TRPC1 mRNA and protein expression, whereas it had no effect on TRPC3, TRPC4, or TRPC5 expression. The TRPC1 expression was associated with increased Ca2+ influx after intracellular Ca2+ store depletion with either thrombin or thapsigargin. We cloned the 5'-regulatory region of the human TRPC1 (hTRPC1) gene which contained a TATA box and CCAAT sequence close to the transcription initiation site. We also identified four nuclear factor-kappaB (NF-kappaB)-binding sites in the 5'-regulatory region. To address the contribution of NF-kappaB in the mechanism of TRPC1 expression, we determined the effects of TNF-alpha on expression of the reporter luciferase after transfection of hTRPC1 promoter-luciferase (hTRPC1-Pro-Luc) construct in the human dermal microvascular endothelial cell line. Reporter activity increased >4-fold at 4 h after TNF-alpha challenge. TNF-alpha-induced increase in reporter activity was markedly reduced by co-expression of either kinase-defective IKKbeta kinase mutant or non-phosphorylatable IkappaB mutant. Treatment with NEMO-binding domain peptide, which prevents NF-kappaB activation by selectively inhibiting IKKgamma interaction with IKK complex, also blocked the TNF-alpha-induced TRPC1 expression. Thus, TNF-alpha induces TRPC1 expression through an NF-kappaB-dependent pathway in endothelial cells, which can trigger augmented Ca2+ entry following Ca2+ store depletion. The augmented Ca2+ entry secondary to TRPC1 expression may be an important mechanism of endothelial injury induced by TNF-alpha.

Reduction of chemokine IL-8 and RANTES expression in human bronchial epithelial cells by a sea-water derived saline through inhibited nuclear factor-kappaB activation

The NaCl content of airway surface fluid is believed to be of central importance in lung pathology. To test whether the Na+ concentration could influence the inflammatory response in human bronchial epithelial cells (BECs), we investigated the interleukin (IL)-8 and RANTES expression in BECs exposed to an isotonic sea-water derived low Na+ (ISW) saline compared to isotonic 0.9% NaCl saline. Exposure of BECs to ISW saline caused a significant decrease in IL-8 and RANTES gene expression and protein production as compared to that observed with 0.9% NaCl saline. Furthermore, we observed a concomitant reduction of phosphorylated IkappaBalpha associated with a marked inhibition of NF-kappaB-DNA binding activity in BECs exposed to ISW saline as compared to 0.9% NaCl saline. These findings support a new role for Na+ in the pathogenesis of airway inflammatory disorders. Therapies targeted at lowering Na+ level in airway epithelium may be beneficial in treating inflammatory lung diseases.

Interferon-tau blocks the stimulatory effect of tumor necrosis factor-alpha on prostaglandin F2alpha synthesis by bovine endometrial stromal cells

Tumor necrosis factor-alpha (TNFalpha) has been shown to be a potent stimulator of prostaglandin (PG) F2alpha synthesis in bovine endometrial stromal cells. The aims of the present study were to determine the effect of interferon-tau (IFNtau) on TNFalpha-stimulated PGF2alpha synthesis and the intracellular mechanisms of TNFalpha and IFNtau action in the stromal cells. When cultured bovine stromal cells were exposed to TNFalpha (0.006-0.6 nM) for 24 h, the production of PGF2alpha and cyclooxygenase (COX)-2 gene expression were stimulated by TNFalpha (0.06-0.6 nM, P < 0.05). Moreover, a specific COX-2 inhibitor (NS-398; 5 nM) blocked the stimulatory effect of TNFalpha on PGF2alpha production (P < 0.05). Although IFNtau (0.03-30 ng/ml) did not stimulate basal PGF2alpha production in the stromal cells, it suppressed TNFalpha action in PGF2alpha production dose dependently (P < 0.05). Moreover, the stimulatory effect of TNFalpha (0.6 nM) on COX-2 gene expression was completely blocked by IFNtau (30 ng/ml; P < 0.05), although the gene expression of COX-2 was not influenced by IFNtau. The overall results indicate that the stimulatory effect of TNFalpha on PGF2alpha production is mediated by the up-regulation of COX-2 gene expression and suggest that one of the mechanisms of the inhibitory effect of IFNtau on luteolysis is the inhibition of TNFalpha action in PGF2alpha production in the stromal cells by the down-regulation of COX-2 gene expression stimulated by TNFalpha.

In vitro anti-inflammatory activity of Phlebodium decumanum. Modulation of tumor necrosis factor and soluble TNF receptors

The immunomodulatory activity of a standardized water soluble fraction of the fern Phlebodium decumanum (EXPLY-37) previously shown to have "in vivo" anti-inflammatory activity was analyzed "in vitro". This extract inhibited tumor necrosis factor (TNF) production by macrophages activated with lipopolysaccharide (LPS) or LPS plus interferon (IFN)-gamma. In contrast, nitric oxide (NO) and interleukin (IL)-1beta production were not affected in the same cultures, whereas IL-6 production was partially inhibited. More interestingly, EXPLY-37 increased the release of soluble TNF-receptor 2 (sTNFR2) and of IL-1R antagonist (IL-1Ra) but not of sTNFR1, by activated macrophages. EXPLY-37 had no effect on T lymphocyte activation, measured as proliferation as well as expression of early and late cell surface antigens CD69, CD25 (IL-2R-alpha) and CD71 (transferrin receptor) at the cell membrane. At the molecular level, EXPLY-37 did not inhibit the activation of the nuclear factor kappa B (NF-kappaB) transcription factor by TNF. In summary, EXPLY-37 has two anti-inflammatory activities "in vitro": it decreases TNF production and increases IL-1Ra and sTNFR2, which may be able to neutralize IL-1 and TNF activity, respectively.

A novel structural class of potent inhibitors of NF-kappa B activation: structure-activity relationships and biological effects of 6-aminoquinazoline derivatives

In this study, we have investigated the roles of substituents on the terminal phenyl ring at the C(4)-position of the quinazoline core to complete the structure-activity relationships (SARs) of our NF-kappa B activation inhibitors. Among them, compound 12j afforded highly potent inhibitory activity toward NF-kappa B transcriptional activation with IC(50) value of 2 nM, along with an excellent in vivo efficacy by reducing the edema formation seen in carrageenin-induced inflammation of the rat hind paw.

Fluid shear-induced NFkappaB translocation in osteoblasts is mediated by intracellular calcium release

Bone formation in response to exogenous mechanical loading is dependent on prostaglandin synthesis by the inducible isoform of cyclooxygenase, COX-2. While several transcription factors target the COX-2 gene, we examined the role of nuclear factor kappa B (NFkappaB) on COX-2 upregulation in osteoblasts in response to fluid shear due to its involvement in immune and inflammatory responses in other cell types. Application of 12 dyn/cm2 laminar flow to MC3T3-E1 osteoblast-like cells resulted in translocation of NFkappaB to the nucleus within 1 h of the onset of shear, with NFkappaB returning to the cytoplasm after 2 h of continuous flow. NFkappaB translocation in response to shear was inhibited by the protease inhibitor, Nalpha-p-tosyl-L-lysine chloromethylketone hydrochloride (TLCK), or a cell-permeant peptide that blocks the nuclear localization sequence (NLS) on NFkappaB. Block of NFkappaB translocation with these inhibitors blocked the shear-induced upregulation of COX-2. We found that disruption of the actin cytoskeleton with cytochalasin D or microtubules with nocodozol did not alter NFkappaB translocation in response to shear. However, addition of the intracellular Ca2+ chelator BAPTA completely blocked NFkappaB translocation. While block of Ca2+ entry with channel blockers failed to inhibit NFkappaB translocation, inhibition of phospholipase C (PLC)-induced intracellular Ca2+ release with the PLC inhibitor U73122 completely abrogated the NFkappaB response to shear. These data indicate that NFkappaB translocation to the nucleus is essential for the fluid shear-induced increase in COX-2. Further, these studies suggest that intracellular Ca2+ release, but not the cytoskeletal architecture, is important to NFkappaB translocation.

Cytokine-regulatory activity and therapeutic efficacy of cinnamyl derivatives in endotoxin shock

We characterized the regulatory activity of cinnamyl derivatives and related compounds on pro-inflammatory cytokine production in vitro and in vivo. Among the 51 compounds examined, 7-amino-4-methylcoumarin (AMC) suppressed the production of interleukin-1alpha, interleukin-6 and tumor necrosis factor (TNF)-alpha, and their lipopolysaccharide-induced mRNAs in P388D1 cells. AMC suppressed pro-inflammatory cytokine transcription by reducing the DNA-binding amounts of nuclear factor-kappaB (NF-kappaB) and activator protein 1. Further, oral administration of AMC (30 mg/kg) as well as anti-TNF-alpha and anti-interleukin-1alpha antibodies significantly prevented death from endotoxin shock in mice without body weight loss and toxicity. AMC did not affect basal cytokine levels in control mice but suppressed the rise of systemic pro-inflammatory cytokine level, especially TNF-alpha. Thus, AMC might contribute to the recovery of endotoxin shock mainly by suppressing pro-inflammatory cytokine transcription. AMC may be useful in understanding the regulation and role of cytokine production in the pathogenesis of cytokine-mediated diseases.

Prevention of diabetes in NOD mice by administration of dendritic cells deficient in nuclear transcription factor-kappaB activity

Abnormalities of dendritic cells (DCs) have been identified in type 1 diabetic patients and in nonobese diabetic (NOD) mice that are associated with augmented nuclear transcription factor (NF)-kappaB activity. An imbalance that favors development of the immunogenic DCs may predispose to the disease, and restoration of the balance by administration of DCs deficient in NF-kappaB activity may prevent diabetes. DCs propagated from NOD mouse bone marrow and treated with NF-kappaB-specific oligodeoxyribonucleotide (ODN) in vitro (NF-kappaB ODN DC) were assessed for efficacy in prevention of diabetes development in vivo. Gel shift assay with DC nuclear extracts confirmed specific inhibition of NF-kappaB DNA binding by NF-kappaB ODN. The costimulatory molecule expression, interleukin (IL)-12 production, and immunostimulatory capacity in presenting allo- and islet-associated antigens by NF-kappaB ODN DC were significantly suppressed. NF-kappaB ODN renders DCs resistant to lipopolysaccharide stimulation. Administration of 2 x 10(6) NF-kappaB ODN DCs into NOD mice aged 6-7 weeks effectively prevented the onset of diabetes. T-cells from pancreatic lymph nodes of NF-kappaB ODN DC-treated animals exhibited hyporesponsiveness to islet antigens with low production of interferon-gamma and IL-2. These findings provide novel insights into the mechanisms of autoimmune diabetes and may lead to development of novel preventive strategies.

Injury and repair in lung and airways

Acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) are common causes of morbidity and mortality in the intensive care unit. ALI/ARDS occurs as a result of systemic inflammation, usually triggered by a microorganism. Activation of leukocytes and release of proinflammatory mediators from multiple cellular sources result in both local and distant tissue injury. Tumor necrosis factor-alpha and interleukin-1 beta are the best characterized of the proinflammatory cytokines contributing to ALI/ARDS and subsequent fibrosis. The ultimate clinical course of ALI/ARDS often is determined by the ability of the injured lung to repopulate the alveolar epithelium with functional cells. Death may occur when fibrosis predominates the healing response, as it results in worsening lung compliance and oxygenation. The rodent bleomycin model of lung fibrosis allows the use of molecular tools to dissect the cellular and subcellular processes leading to fibrosis. The elements of this response may provide therapeutic targets for the prevention of this devastating complication of ALI/ARDS.

Effect of CD14 blockade on endotoxin-induced acute lung injury in mice

CD14 functions as a cell surface receptor for endotoxin (lipopolysaccharide [LPS]) and is thought to have an essential role in innate immune responses to infection. Previous studies have revealed attenuation of the systemic response after sepsis by blocking CD14. In this study, we tested the hypothesis that CD14 blockade protects against inflammatory responses associated with LPS pneumonia. We examined the effect of an anti-murine CD14 monoclonal antibody (4C1) on the development of acute lung injury induced by intratracheal LPS in mice. We also measured the production of cytokines (tumor necrosis factor-alpha, interleukin-6, and macrophage inflammatory protein-2) and nitric oxide by murine peritoneal macrophages exposed to LPS in vitro. Nuclear factor (NF)-kappa B translocation was evaluated in nuclear extracts from lung homogenates. 4C1 significantly attenuated pulmonary edema and neutrophil emigration after LPS administration. The production of cytokines and nitric oxide by LPS-stimulated macrophages was significantly decreased by 4C1 treatment. NF-kappa B translocation induced by LPS instillation was also suppressed by 4C1. These results suggest that blockade of CD14 might attenuate acute lung injury after intratracheal instillation of LPS through the suppression of NF-kappa B translocation. The inhibitory effect of CD14 blockade on cytokine production and nitric oxide release of macrophages might contribute to the attenuation of lung injury.

Impaired degradation of inhibitory subunit of NF-kappa B (I kappa B) and beta-catenin as a result of targeted disruption of the beta-TrCP1 gene

beta-TrCP1 (also known as Fbw1a or FWD1) is the F-box protein component of an Skp1/Cul1/F-box (SCF)-type ubiquitin ligase complex. Although biochemical studies have suggested that beta-TrCP1 targets inhibitory subunit of NF-kappa B(I kappa B) proteins and beta-catenin for ubiquitylation, the physiological role of beta-TrCP1 in mammals has remained unclear. We have now generated mice deficient in beta-TrCP1 and shown that the degradation of I kappa B alpha and I kappa B beta is reproducibly, but not completely, impaired in the cells of these animals. The nuclear translocation and DNA-binding activity of NF-kappa B as well as the ability of this transcription factor to activate a luciferase reporter gene were also inhibited in beta-TrCP1-/- cells compared with those apparent in wild-type cells. The subcellular localization of beta-catenin was altered markedly in beta-TrCP1-/- cells. Furthermore, the rate of proliferation was reduced and both cell size and the percentage of polyploid cells were increased in embryonic fibroblasts derived from beta-TrCP1-/- mice compared with the corresponding wild-type cells. These results suggest that beta-TrCP1 contributes to, but is not absolutely required for, the degradation of I kappa B and beta-catenin and the consequent regulation of the NF-kappa B and Wnt signaling pathways, respectively. In addition, they implicate beta-TrCP1 in the maintenance of ploidy during cell-cycle progression.

Human herpesvirus 8 K1-associated nuclear factor-kappa B-dependent promoter activity: role in Kaposi's sarcoma inflammation?

BACKGROUND

The growing number of human immunodeficiency virus type 1 (HIV-1) infections worldwide and the increasing use of immunosuppressive modalities for organ transplantation have contributed to an epidemic of Kaposi's sarcoma (KS), which has been etiologically linked to human herpesvirus 8 (HHV8) or KS-associated virus. Since the onset of the acquired immunodeficiency syndrome epidemic, inflammation has been recognized as an essential component of KS pathology. HHV8 bears a gene (K1) encoding a transmembrane protein with an immunoreceptor tyrosine-based activation motif. This motif is present in receptors that mediate inflammation.

PURPOSE

To dissect the cellular effects of K1 function and the eventual role of K1 in KS, we developed a cell model for studying K1 expression.

METHODS

K1 was cloned from BC-3 lymphoma cells. To monitor transcriptional activation, K1 was coexpressed with plasmids containing luciferase under control of various promoters. K1 expression was monitored by indirect immunofluorescence and by combined immunoprecipitation/immunoblot analysis. Inflammatory cytokines were measured by enzyme-linked immunosorbent assay.

RESULTS

Cellular transfection of the K1 gene induced reporter expression under control of nuclear factor-kappa B (NF-kappaB), which controls the transcription of numerous proteins involved in inflammation. Treatment of cells with aspirin, an agent that targets this intracellular pathway and blocks cell inflammatory responses, blocked K1-induced NF-kappaB-dependent promoter activity. When a second KS cofactor, i.e., the HIV-1-transactivating gene tat, was coexpressed with K1, we observed an additive effect on NF-kappaB-dependent transcription. K1 transfection stimulated the secretion of cytokines interleukin (IL) 6, granulocyte-macrophage colony-stimulating factor, and IL-12. Cells treated with the conditioned media of K1 transfectants exhibited similar characteristics of K1 transfectants, indicating that a paracrine loop was being activated.

CONCLUSION

Thus, K1 may activate cells in which it is expressed, as well as other cells in a paracrine manner. K1 cooperates in signaling with HIV-1 Tat, suggesting that both of the proteins from these viruses converge to reach an enhanced level of inflammation that may underlie progressive KS.

Role for complement in mediating intestinal nitric oxide synthase-2 and superoxide dismutase expression

Inducible nitric oxide synthase (iNOS) and superoxide dismutase (SOD) play an important role in the pathology of ischemia-reperfusion. This study sought to determine if the proinflammatory effects of complement modulate iNOS and SOD in the rat after gastrointestinal ischemia and reperfusion (GI/R). An inhibitory or noninhibitory anti-complement component 5 (C5) monoclonal antibody (18A or 16C, respectively) was administered before GI/R. RT-PCR revealed a significant increase in intestinal iNOS mRNA compared with sham after GI/R that was attenuated significantly by 18A. Immunohistochemistry demonstrated increased iNOS protein expression within the intestinal crypts after GI/R. Cu/Zn SOD (mRNA and protein) was unaffected by GI/R, whereas Cu/Zn SOD activity was reduced significantly. Mn SOD protein expression was decreased significantly by GI/R. Anti-C5 preserved Cu/Zn SOD activity and Mn SOD protein expression. Staining for nitrotyrosine showed that anti-C5 treatment reduced protein nitration in the reperfused intestine. Immunohistochemistry demonstrated prominent phosphorylated (p) inhibitory factor-kappaB (IkappaB)-alpha staining of intestinal tissue after GI/R, whereas anti-C5 reduced p-IkappaB-alpha expression. These data indicate that complement may mediate tissue damage during GI/R by increasing intestinal iNOS and decreasing the activity and protein levels of Cu/Zn SOD and Mn SOD, respectively.

The PPARgamma ligand, 15d-PGJ2, attenuates the severity of cerulein-induced acute pancreatitis

INTRODUCTION

The prostaglandin D2 metabolite, 15d-PGJ2, a potent natural ligand for peroxisome proliferator-activated receptor gamma (PPARgamma), exerts antiinflammatory effects by inhibiting the induction of inflammatory response genes and NF-kappaB-dependent transcription. AIM To determine whether 15d-PGJ2 decreases the severity of secretagogue-induced acute pancreatitis (AP) and to assess cellular mechanisms contributing to these effects. METHODOLOGY Swiss Webster mice were injected with either saline or cerulein (50 microg/kg) hourly for 8 hours and received either 15d-PGJ2 (2 mg/kg) or vehicle 1 hour before and 4 hours after induction of AP. RESULTS Treatment with 15d-PGJ2 significantly attenuated AP, as determined by histologic assessment of edema, vacuolization, inflammation, and necrosis. This attenuation was associated with decreased cyclooxygenase-2 (COX-2) and intercellular adhesion molecule-1 (ICAM-1) expression and decreased serum and pancreatic IL-6 levels. Treatment with 15d-PGJ2 markedly inhibited NF-kappaB DNA-binding activity, and, moreover, this decreased activity was associated with a concomitant inhibition of IkappaB protein degradation. CONCLUSION Our findings demonstrate that 15d-PGJ2 attenuates the severity of AP most likely through the inhibition of COX-2 expression, IL-6 production, and NF-kappaB activation. Ligands specific for PPARgamma may represent novel and effective means of clinical therapy for AP.

Nuclear factor-kappaB and its role in sepsis-associated organ failure

Nuclear factor (NF)-kappaB is involved in regulating the transcription of many of the immunomodulatory mediators involved in the development of sepsis-induced organ failure. Kinase pathways involving p38 and Akt and initiated by engagement of Toll-like receptors modulate transcriptional activity of NF-kappaB, but apparently through different mechanisms. Increased activation of NF-kappaB occurs with sepsis, and greater levels of nuclear accumulation of NF-kappaB are associated with higher rates of mortality and worse clinical outcome. The percentage of apoptotic neutrophils is reduced in sepsis, and inhibition of nuclear translocation of NF-kappaB restores neutrophil apoptosis to baseline levels. In models of sepsis, suppression of NF-kappaB activation decreases acute inflammatory processes and organ dysfunction. Because NF-kappaB occupies a central role in signaling pathways important in sepsis, modulation of NF-kappaB activity may be an appropriate therapeutic target in patients with sepsis.

TNF-related weak inducer of apoptosis receptor, a TNF receptor superfamily member, activates NF-kappa B through TNF receptor-associated factors

TNF-related weak inducer of apoptosis (TWEAK) is a member of the TNF ligand family that induces angiogenesis in vivo. The TWEAK receptor (TweakR) is a recently identified member of the TNF receptor (TNFR) superfamily and is expressed on smooth muscle cells (SMCs) and endothelial cells (ECs). In this report we identify the TNF receptor-associated factor (TRAF) family of signal transducers as important components of TweakR-mediated NF-kappa B activation. Coimmunoprecipitation experiments suggested potential interactions between the cytoplasmic tail of TweakR with TRAFs 1, 2, 3, and 5. Dominant negative forms of TRAF2 and TRAF5 substantially inhibited TweakR-mediated NF-kappa B activation, suggesting a role of TRAFs in regulating smooth muscle and endothelial cell function. Using alanine-scanning analysis, we defined a TRAF-binding motif, PIEET, in TweakR that mediates TRAF binding and NF-kappa B activation. Furthermore, TweakR mutations within the TRAF-binding motif abolished TweakR-stimulated SMC migration, revealing a role for TRAFs in TweakR-induced activation events.

Modulation of IL-12 p35 and p40 promoter activity by smokeless tobacco extract is associated with an effect upon activation of NF-kappaB but not IRF transcription factors

Interleukin (IL)-12 (p70), composed of p35 and p40 subunits, stimulates cellular immunity and inflammation. Stimulation of IL-12 production by smokeless tobacco extract (STE) could increase the chances of oral inflammatory disease. However, p40 forms homodimers and is part of IL-23 heterodimers. Expression of p35 and p40 in response to lipopolysaccharide (LPS) and interferon (IFN)-gamma requires activation of nuclear factor-kappa-B (NF-kappaB) and interferon regulatory factor (IRF) transcription factors. To determine the impact of STE on expression of p35 and p40, the activities of p35 and p40 promoter reporter plasmids in RAW264.7 cells stimulated with STE alone or in the presence of IFN-gamma and LPS were assessed. In addition, nuclear localizations of NF-kappaB p50, p65 and IRF-1, -2 and -8 in RAW264.7 cells treated with STE were evaluated. The results show that STE alone stimulates p40 and p35 promoter activity and enhances IFN-gamma-induced p40 and p35 promoter activity. In contrast, STE had no effect on LPS-induced p35 and p40 promoter activity and diminished IFN-gamma/LPS-induced p35 promoter activity. STE had little effect upon nuclear localization of IRFs, but it stimulated nuclear localization of both NF-kappaB p50 and p65. STE also stimulated IFN-gamma-induced activation of NF-kappaB p50 but reduced nuclear localization of IFN-gamma- and IFN-gamma/LPS-induced NF-kappaB p65. SN50, an inhibitor of NF-kappaB nuclear localization, significantly lowered STE-induced p35 and p40 promoter activity. These results suggest that STE stimulation of bioactive IL-12 production is correlated with its impact upon both p35 and p40 and can be attributed in part through an effect upon NF-kappaB p50 nuclear localization.

Inhibition of lipopolysaccharide-inducible nitric oxide synthase, TNF-alpha and COX-2 expression by sauchinone effects on I-kappaBalpha phosphorylation, C/EBP and AP-1 activation

1. Sauchinone, a lignan isolated from Saururus chinensis (Saururaceae), is a diastereomeric lignan with cytoprotective and antioxidant activities in cultured hepatocytes. The effects of sauchinone on the inducible nitric oxide synthase (iNOS), tumor necrosis factor-alpha (TNF-alpha) and cyclooxygenase 2 (COX-2) gene expression and on the activation of transcription factors, nuclear factor-kappaB (NF-kappaB), CCAAT/enhancer-binding protein (C/EBP), activator protein-1 (AP-1) and cAMP-response element-binding protein (CREB) were determined in Raw264.7 cells as part of the studies on its anti-inflammatory effects. 2. Expression of the iNOS, TNF-alpha and COX-2 genes was assessed by Northern and Western blot analyses. NO production was monitored by chemiluminescence detection using a NO analyzer. To identify the transcriptional factors affected by sauchinone, the extents of NF-kappaB, C/EBP, AP-1 and CREB activation were measured. Activation of the transcription factors was monitored by gel mobility shift assay, whereas p65 and I-kappaBalpha were analyzed by immunocytochemical and immunoblot analyses. 3. Sauchinone inhibited the induction of iNOS, TNF-alpha and COX-2 by lipopolysaccharide (LPS) (IC50</=10 micro M) with suppression of the mRNAs. 4. Sauchinone (1-30 micro M) inhibited LPS-inducible nuclear NF-kappaB activation and nuclear translocation of p65, which was accompanied by inhibition of I-kappaBalpha phosphorylation. 5. LPS-inducible increase in the intensity of C/EBP binding to its consensus sequence was also inhibited by sauchinone. The AP-1, but not CREB, DNA binding activity was weakly inhibited by sauchinone. 6. These results demonstrate that sauchinone inhibits LPS-inducible iNOS, TNF-alpha and COX-2 expression in macrophages through suppression of I-kappaBalpha phosphorylation and p65 nuclear translocation and of C/EBP and/or AP-1 activation, which may constitute anti-inflammatory effects of the lignan.

Mild hypothermia inhibits nuclear factor-kappaB translocation in experimental stroke

Nuclear factor-kappaB (NFkappaB) is a transcription factor that is activated after cerebral ischemia. NFkappaB activation leads to the expression of many inflammatory genes involved in the pathogenesis of stroke. The authors previously showed that mild hypothermia is protective even when cooling begins 2 h after stroke onset. In the present study, they examined the influence of hypothermia on NFkappaB activation. Rats underwent 2 h of transient middle cerebral artery occlusion. Brains were cooled to 33 degrees C immediately after or 2 h after occlusion, and maintained for 2 h. After normothermic ischemia (brain temperature at 38 degrees C), NFkappaB cytoplasmic expression, nuclear translocation, and binding activity were observed as early as 2 h in the ischemic hemisphere and persisted at 24 h. Hypothermia decreased NFkappaB translocation and binding activity but did not alter overall expression. Hypothermia also affected the levels of NFkappaB regulatory proteins by suppressing phosphorylation of NFkappaB's inhibitory protein (IkappaB-alpha) and IkappaB kinase (IKK-gamma) and decreasing IKK activity, but did not alter overall IKK levels. Hypothermia suppressed the expression of two NFkappaB target genes: inducible nitric oxide synthase and TNF-alpha. These data suggest that the protective effect of hypothermia on cerebral injury is, in part, related to NFkappaB inhibition due to decreased activity of IKK.

Regulatory RNA induces the production of IFN-gamma, but not IL-4 in human lymphocytes: role of RNA-dependent protein kinase (PKR) and NF-kappaB

Previous results with p9-RNA, obtained from lymph nodes of animals immunized with the peptide p9 of HIV-1, suggested that its effects on lymphocytes could be mediated by RNA-dependent protein kinase (PKR). Here we report that p9-RNA activates PKR leading to the degradation of the inhibitor I-kappaB alpha and the concomitant nuclear factor kappa B (NF-kappaB) activation. The fractionation of p9-RNA by affinity chromatography indicates that the poly A(+) p9-RNA is the fraction responsible for PKR activation. We also found that p9-RNA induces the production of interferon-gamma (IFN-gamma), but not interleukin (IL-4) since only IFN-gamma gene promoter contains NF-kappaB binding site. This study provides the first evidence that transcriptional control of gene expression by regulatory RNAs can be mediated by PKR through NF-kappaB activation. A model for the mechanism of action of poly A(+) p9-RNA is proposed.