Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:P43026 (lipopolysaccharide)
 62,215 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The B cell-specific transcription factor Pax-5 has been shown previously to interact with the promoter of the blk gene in vitro. blk encodes a tyrosine kinase associated with the B cell receptor, which is expressed during the early but not the final stages of B cell development. To investigate whether Pax-5 regulates expression of the blk gene in vivo during B cell development and/or activation, Pax-5a was overexpressed in B cell lines. Increases in blk promoter activity using a chloramphenicol acetyltransferase reporter gene system suggested a role for Pax-5a as a transcriptional activator. Subsequent site-specific mutagenesis studies showed that mutations of the Pax-5 binding site on blk significantly alter promoter activity, although results suggested that other factors could bind to this region as well. Using mobility shift assays, we detected an inducible transcription factor that interacts strongly with a sequence overlapping the Pax-5 site on the blk promoter and identified this as a homodimer of NF-kappaB/p50, a member of the NF-kappaB/Rel family of transcription factors. This factor was present at high levels in lipopolysaccharide-activated normal B cells and in plasma cell lines but either at low levels or undetectable levels in resting normal B cells or pre-B or mature B cell lines. In contrast, lipopolysaccharide induction of a pre-B cell line (703/Z) induced a complex that contained both NF-kappaB/p50 and p65. These studies suggest that different NF-kappaB complexes are able to interact with a sequence overlapping the Pax-5 site on the blk promoter and that the relative levels of "bound" factor influence levels of blk expression. Since p50 homodimers and p50/p65 heterodimers of the NF-kappaB complex should have opposing effects on blk transcription, this could provide a mechanism to differentially regulate blk expression during B cell development and activation.
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PMID:The transcription factor NF-kappaB/p50 interacts with the blk gene during B cell activation. 966 Aug 39

The endogenous pyrogen interleukin-1 (IL-1) is considered as one of the key molecules in orchestrating the host response of injury and inflammation. IL-1 exerts its effects upon binding to the type I IL-1 receptor (IL-1RI). The IL-1-IL-1RI complex is further thought to associate with the IL-1 receptor accessory protein (IL-1RAcP), which is suggested to be important for most IL-1 signal transduction pathways. With the aim of investigating the importance of the IL-1RAcP in IL-1 signalling, IL-1alpha and IL-1beta induced febrile responses and IL-1beta-mediated activation of NFkappaB in primary astrocyte cultures were examined using IL-1RAcP-deficient (IL-1RAcP KO) and wild type mice, respectively. It was shown that neither recombinant rat IL-1alpha (rrIL-1alpha, 25 microg/kg), recombinant rat IL-1beta (rrIL-1beta, 40 microg/kg) nor recombinant human IL-1beta (rhIL-1beta, 50 microg/kg) injected i.p. could elicit febrile responses in the IL-1RAcP-deficient mice, while the same doses of rrIL-1alpha/beta or rhIL-1beta injected into wild type mice caused normal fever responses. A febrile response could be induced in the IL-1RAcP-deficient mice by i.p. administration of E. coli lipopolysaccharide (LPS, 50 microg/kg) and this response was similar to that obtained in wild type mice. Furthermore, it was shown that rhIL-1beta activated, in a concentration-dependent manner, nuclear translocation of the transcriptional nuclear factor kappa B (NFkappaB) in primary astrocyte cultures prepared from wild type mice, whereas no IL-1beta-induced translocation of NFkappaB could be detected in cultures prepared from IL-1RAcP-deficient mice, as revealed by electrophoretic mobility shift assay (EMSA). The rhIL-1beta-induced NFkappaB complexes were shown to contain p50 but no, or very little, p65 and cRel immunoreactive proteins.
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PMID:Interleukin-1-mediated febrile responses in mice and interleukin-1 beta activation of NFkappaB in mouse primary astrocytes, involves the interleukin-1 receptor accessory protein. 968 88

We describe a dense cluster of DNA-protein interactions located 600 nucleotides upstream of the transcriptional start site of the human tumor necrosis factor (TNF) gene. This area was identified as being of potential importance for lipopolysaccharide-inducible TNF expression in the human monocyte cell line Mono Mac 6, based on reporter gene analysis of point mutations at a number of nuclear factor kappaB (NF-kappaB)-like motifs within the human TNF promoter region. The area contains two NF-kappaB sites, which are here shown by DNase I and methylation interference footprinting to flank a novel binding site. UV cross-linking studies reveal that the novel site can also bind NF-kappaB as well as an unknown protein(s) of approximately 40 kDa. We show that these three adjacent kappaB-binding sites differ markedly in their relative affinities for p50/p50, p65/p65, and p65/p50, yet this 39-nucleotide segment of DNA appears capable of binding up to three NF-kappaB heterodimers simultaneously. Reporter gene studies indicate that each element of the cluster contributes to lipopolysaccharide-induced transcriptional activation in Mono Mac 6 cells. These findings suggest that NF-kappaB acts in a complex manner to activate TNF transcription in human monocytes.
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PMID:Complex NF-kappaB interactions at the distal tumor necrosis factor promoter region in human monocytes. 969 74

Antibodies of the immunoglobulin G1 class are induced in mice by T-cell-dependent antigens but not by lipopolysaccharide (LPS). CD40 engagement contributes to this preferential isotype production by activating NF-kappaB/Rel to induce germ line gamma1 transcripts, which are essential for class switch recombination. Although LPS also activates NF-kappaB, it poorly induces germ line gamma1 transcripts. Western blot analyses show that CD40 ligand (CD40L) induces all NF-kappaB/Rel proteins, whereas LPS activates predominantly p50 and c-Rel. Electrophoretic mobility shift assays show that in CD40L-treated cells, p50-RelA and p50-RelB dimers are the major NF-kappaB complexes binding to the germ line gamma1 promoter, whereas in LPS-treated cells, p50-c-Rel and p50-p50 dimers are the major binding complexes. Transfection of expression plasmids for NF-kappaB/Rel fusion proteins (forced dimers) indicates that p50-RelA and p50-RelB dimers activate the germ line gamma1 promoter and that p50-c-Rel and p50-p50 dimers inhibit this activation by competitively binding to the promoter without activating the promoter. Therefore, germ line gamma1 transcription depends on the composition of NF-kappaB/Rel proteins.
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PMID:The ability of CD40L, but not lipopolysaccharide, to initiate immunoglobulin switching to immunoglobulin G1 is explained by differential induction of NF-kappaB/Rel proteins. 971 Jun 36

Macrophages are a major source of proinflammatory cytokines such as tumor necrosis factor alpha (TNF-alpha), which are expressed during conditions of inflammation, infection, or injury. We identified an activity secreted by a macrophage tumor cell line that negatively regulates bacterial lipopolysaccharide (LPS)-induced expression of TNF-alpha. This activity, termed TNF-alpha-inhibiting factor (TIF), suppressed the induction of TNF-alpha expression in macrophages, whereas induction of three other proinflammatory cytokines (interleukin-1beta [IL-1beta], IL-6, and monocyte chemoattractant protein 1) was accelerated or enhanced. A similar or identical inhibitory activity was secreted by IC-21 macrophages following LPS stimulation. Inhibition of TNF-alpha expression by macrophage conditioned medium was associated with selective induction of the NF-kappaB p50 subunit. Hyperinduction of p50 occurred with delayed kinetics in LPS-stimulated macrophages but not in fibroblasts. Overexpression of p50 blocked LPS-induced transcription from a TNF-alpha promoter reporter construct, showing that this transcription factor is an inhibitor of the TNF-alpha gene. Repression of the TNF-alpha promoter by TIF required a distal region that includes three NF-kappaB binding sites with preferential affinity for p50 homodimers. Thus, the selective repression of the TNF-alpha promoter by TIF may be explained by the specific binding of inhibitory p50 homodimers. We propose that TIF serves as a negative autocrine signal to attenuate TNF-alpha expression in activated macrophages. TIF is distinct from the known TNF-alpha-inhibiting factors IL-4, IL-10, and transforming growth factor beta and may represent a novel cytokine.
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PMID:Tumor necrosis factor alpha transcription in macrophages is attenuated by an autocrine factor that preferentially induces NF-kappaB p50. 974 85

Repeated exposure to bacterial endotoxin causes a diminished response by the host to further exposure. One important feature of this hyporesponsiveness is a reduced macrophage production of nitric oxide (NO) via the inducible nitric oxide synthase (iNOS) pathway. Using a murine macrophage model, we observed that hyporesponsiveness was accompanied by a decrease in the levels of NO release (measured as nitrite), iNOS protein and iNOS gene transcription. The expression of the putative lipopolysaccharide (LPS) receptor, CD14, was not altered. In vivo genomic footprinting showed that the same binding sites are occupied in the iNOS promoter and enhancer of desensitized macrophages and of LPS-responsive macrophages, yet the composition of NF-kappaB in the nuclei of these cells was found to be altered. The transcriptionally inactive homodimer p50-p50 represented the predominant binding activity in nuclei from LPS-pretreated cells before and after stimulation. Nuclei from cells which had not been pretreated but were stimulated contained more of the transcriptionally active p50-p65 heterodimer than their pretreated counterparts. Consistent with this, the cytosolic steady-state level of an inhibitor of NF-kappaB activity, I-kappaBalpha, was decreased in normal cells but not in pretreated cells. We propose that the presence of an overwhelming excess of transcriptionally inactive p50 homodimers on their kappaB sites in the iNOS control region in pretreated cells may block kappaB site binding by p50-p65, thereby reducing the activity of the protein complex governing iNOS transcription.
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PMID:Hyporesponsiveness to lipopolysaccharide alters the composition of NF-kappaB binding to the regulatory regions of inducible nitric oxide synthase gene. 975 83

STAT6, NF-kappaB (p50) and C/EBPbeta transcription factors (TF) were examined with respect to CD23 regulation. Electrophoretic mobility shift assay (EMSA), competition and supershift analysis demonstrated that STAT6 binds the CD23a promoter but with a lower affinity than the consensus site. STAT6-/- mice were analyzed for CD23 levels and showed reduced expression after CD40 ligand trimer (CD40LT) stimulation. However, normal CD23 expression and even some IgE production was induced in STAT6-/- mice with CD40LT/IL-4. EMSA analysis indicated that the CD23a STAT site was bound by a protein in nuclear extracts from CD40+/-IL-4-stimulated STAT6-/-B cells. Western blot analysis of these nuclear extracts demonstrated the presence of STAT3 and STAT5, suggesting that these STATs can induce CD23 in this situation. Further supporting evidence was obtained by showing that IL-2 and IL-4 both synergize with CD40 in an identical manner for CD23 induction on STAT6-/- B cells. EMSA analysis of the two putative NF-kappaB sites confirmed binding to both, although one site bound with a higher affinity than the second. Analysis of p50-/-mice indicated that this subunit was not necessary for CD23 induction or CD40/IL-4-induced IgE production. Finally, no role for C/EBP was observed in CD23 induction by EMSA or by CD23 induction analysis in C/EBPbeta-/- mice, whereas the absence of C/EBP, did have an effect on IgE production and lipopolysaccharide-induced B cell proliferation. Based on these data, a model is presented which suggests that CD23 superinduction results from STAT and NF-kappaB interaction.
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PMID:STAT6, NF-kappaB and C/EBP in CD23 expression and IgE production. 979 20

Ethanol (ETOH) selectively suppressed Escherichia coli endotoxin lipopolysaccharide (LPS)-stimulated, but not dibutyryl cAMP (db-cAMP)-stimulated upregulation of inducible nitric oxide synthase (iNOS) in rat alveolar macrophages (AMs) in vivo (Zhao et al., Alcohol. Clin. Exp. Res. 21:1062-1074, 1997). LPS-induced stimulation of iNOS is inhibited in vitro by db-cAMP and purine-2-Y (P2Y) receptor-mediated agonists. We examined the effect of ETOH on this interaction in rat lung AMs in vivo. Two hours after co-administration of LPS [0.6 mg/kg, intratracheal (i.t.)] with db-cAMP (0.1 mg/kg, i.t.) or 2-methylthio-adenosine-triphosphate (2-mes-ATP) to Sprague-Dawley rats (225 to 250 g) (n = 10 to 24/gp) iNOS messenger ribonucleic acid (mRNA), iNOS protein, and nitrate and nitrite anions [reactive nitrogen intermediates (RNIs)] in bronchoalveolar lavage fluid (BALf), and the ex vivo incubates of AMs were increased more than when these compounds were given individually to the rats. Co-administration of LPS with the autacoids did not affect LPS-stimulated increases of tumor necrosis factor-alpha (TNF alpha) mRNA, but inhibited LPS-stimulated BALf TNF alpha protein and attenuated LPS-mediated decreases of cell-associated TNF alpha. Pretreatment of rats with ETOH (4.5 g/kg, i.p.) or diethyidithiocarbamate (DETC; 5 mg/kg, i.t.), an inhibitor of the nuclear transcription factor NF kappa B (NF-kappaB), 30 min before co-administration of LPS with the autacoids restored iNOS mRNA levels to that obtained with the autacoid alone. Pretreatment of rats with ETOH decreased iNOS protein and RNI below that produced by either compound given individually to the rats. Although pretreatment of rats with DETC also decreased iNOS protein and RNI levels produced by LPS, the levels of both substances were elevated above that of the autacoid alone, LPS-induced upregulation of iNOS mRNA was associated with elevated levels of p65/p50 NF-kappaB in the nucleus of AMs. Neither db-cAMP or 2-mes-ATP affected LPS-stimulated NF-kappaB-DNA binding. Moreover, ETOH and DETC inhibited LPS-stimulated NF-kappaB-DNA binding. We conclude that in rat AMs in vivo: (1) both db-cAMP and P2Y-receptor stimulation summate with, rather than inhibit, LPS-induced upregulation of the iNOS mRNA, protein, and RNI; (2) ETOH and DETC inhibit LPS-induced upregulation of iNOS mRNA only when stimulated through the NF-kappaB pathway; and (3) ETOH inhibits both autacoid and LPS-stimulated formation of iNOS protein by a mechanism independent of its ability to suppress iNOS transcription.
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PMID:Ethanol inhibits the potentiation of endotoxin by dibutyryl cAMP and 2-methylthio ATP in vivo. 983 79

Transcription of the IP-10 gene requires interferon (IFN)-stimulated response element (ISRE) and kappaB sites to be induced by lipopolysaccharide (LPS), IFN-gamma, virus, and poly(I:C). A requirement for Stat1 binding to ISRE for IFN-gamma and IFN regulatory factor-1 (IRF-1) binding to ISRE for LPS, poly(I:C), and virus has been reported. We investigated whether viral transcription is required for IP-10 induction and how ISRE interacts with IRF-1 and with two kappaB sites. IP-10 mRNA was induced by Newcastle disease virus and Sendai virus in rat astrocytes and the human astrocytoma U251 cell line. IP-10 was also induced by UV-irradiated virus, which is unable to carry out viral transcription. The minimal IP-10 virus response element (VRE) consists of an ISRE and adjacent kappaB site between -236 and -153, to which p50/p65 NF-kappaB proteins and IRF-like proteins bind. Virus induced NF-kappaB binding to an isolated kappaB sequence adjacent to ISRE. However, no protein binding to isolated ISRE was induced by virus. Virus also induced IP-10 in cells expressing a defective IRF-1 gene. Therefore, effective ISRE activity of IP-10 VRE may require an IRF-like protein binding, which is enhanced by an NF-kappaB heterodimer binding to an adjacent KB site. IRF-1 is not required for virus-induced IP-10 gene expression.
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PMID:IP-10 gene transcription by virus in astrocytes requires cooperation of ISRE with adjacent kappaB site but not IRF-1 or viral transcription. 985 21

We investigated the effect of PGE2 and iloprost (a prostacyclin analogue) on inducible nitric oxide synthase (iNOS) protein expression and nuclear factor-kappaB (NF-kappaB) activation in lipopolysaccharide (LPS)-stimulated J774 macrophages. Incubation of J774 cells with LPS (10 microg/ml) caused an increase of iNOS protein expression which was prevented in a concentration-dependent fashion by PGE2 (0.1, 1, 10 microM) and iloprost (0.01, 0.1, 1 microM). Electrophoretic mobility shift assay indicated that both prostanoids blocked the activation of NF-kappaB, a transcription factor necessary for NO synthase induction. PGE2 and iloprost also blocked disappearance of I kappaB-alpha from cytosolic fraction and nuclear translocation of NF-kappaB subunits p50 and p65. These results show for the first time that PGE2 and iloprost down-regulate iNOS protein expression by inhibiting NF-kappaB activation and suggest a negative feed-back mechanism that may be important for limiting excessive or prolonged NO production in pathological events.
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PMID:Prostaglandins prevent inducible nitric oxide synthase protein expression by inhibiting nuclear factor-kappaB activation in J774 macrophages. 986 29


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