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

A plasma lipopolysaccharide (LPS)-binding protein (LBP) has been shown to regulate the response of rabbit peritoneal macrophages and human blood monocytes to endotoxin (LPS). We investigated whether LBP is present in lung fluids and the effects of LBP on the response of lung macrophages to LPS. Immunoreactive LBP was detectable in the lavage fluids of patients with the adult respiratory distress syndrome by immunoprecipitation followed by Western blotting, and also by specific immunoassay. In rabbits, the LBP appeared to originate outside of the lungs, inasmuch as mRNA transcripts for LBP were identified in total cellular RNA from liver, but not from lung homogenates or alveolar macrophages. Purified LBP enhanced the response of human and rabbit alveolar macrophages to both smooth form LPS (Escherichia coli O111B:4) and rough form LPS (Salmonella minnesota Re595). In the presence of LBP and LPS, the onset of tumor necrosis factor-alpha (TNF alpha) production occurred earlier and at an LPS threshold dose that was as much as 1,000-fold lower for both types of LPS. In rabbit alveolar macrophages treated with LBP and LPS, TNF alpha mRNA appeared earlier, reached higher levels, and had a prolonged half-life as compared with LPS treatment alone. Neither LPS nor LPS and LBP affected pHi or [Cai++] in alveolar macrophages. Specific monoclonal antibodies to CD14, a receptor that binds LPS/LBP complexes, inhibited TNF alpha production by human alveolar macrophages stimulated with LPS alone or with LPS/LBP complexes, indicating the importance of CD14 in mediating the effects of LPS on alveolar macrophages. Thus, immunoreactive LBP accumulates in lung lavage fluids in patients with lung injury and enhances LPS-stimulated TNF alpha gene expression in alveolar macrophages by a pathway that depends on the CD14 receptor. LBP may play an important role in augmenting TNF alpha expression by alveolar macrophages within the lungs.
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PMID:Lipopolysaccharide binding protein enhances the responsiveness of alveolar macrophages to bacterial lipopolysaccharide. Implications for cytokine production in normal and injured lungs. 128 27

Although tumor necrosis factor (TNF) is undoubtedly a major mediator of the antitumor and shock-inducing activities of lipopolysaccharide (LPS), the outcome of a challenge with TNF is highly dependent on the presence or absence of other substances or conditions. We have previously shown that to obtain lethality in mice after TNF administration both TNF receptor (TNF-R) types have to be triggered. This is illustrated by the fact that recombinant human (rh) TNF, which is a selective murine (m) TNF-R55 agonist, is not lethal, whereas mTNF, which binds both mTNF-R55 and mTNF-R75, is lethal in mice. Triggering of TNF-R75 is, however, no longer needed when sensitizers such as galactosamine or low doses of LPS or interleukin (IL)-1 are also present. Here, we report that this selective species specificity of TNF is also reflected in patterns of induced IL-6: both rmTNF and rhTNF could induce considerable IL-6 peak levels in the plasma (up to 10 ng/ml) 2 to 3 h after TNF administration. However, only rmTNF was capable of inducing the same pattern of sustained IL-6 levels previously observed after lethal LPS doses, while rhTNF only caused induction of transient IL-6 levels, as found after nonlethal LPS doses. We also observed that the sensitizer IL-1 could complement rhTNF to induce such a sustained IL-6 induction. Since we were interested in sensitizers with a defined mechanism of action, we further investigated the effects of the glucocorticoid and progesterone inhibitor RU38486 on the lethal and IL-6-inducing properties of TNF. We observed that RU38486 closely mimicked IL-1: both had similar effects on IL-6 induction and sensitized mice to the lethal effects of TNF with comparable efficiency and kinetics. Using a monoclonal anti-IL-1R antibody, we finally observed that the effects of RU38486 were most probably not mediated by IL-1. These observations suggest that a glucocorticoid-antagonistic activity might be a key factor in the pathways leading to septic shock and that such activity could be a key target for the pharmacological manipulation of sepsis.
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PMID:The glucocorticoid antagonist RU38486 mimics interleukin-1 in its sensitization to the lethal and interleukin-6-inducing properties of tumor necrosis factor. 153 65

The regulation of the 55-kDa TNF receptor (TNF-R) mRNA synthesis, membrane expression, and TNF binding factor (BF) release was examined in resting and activated human monocytic THP-1 and human promyelocytic leukemia HL-60 cells in vitro. Cells were activated with phorbol myristate acetate (PMA) and bacterial lipopolysaccharide (LPS). TNF alpha cytolytic activity in the supernatant of THP-1 cells stimulated by PMA began to appear at 4 hr, reached a peak at 8 hr, and declined by 12 hr. For THP-1 cells stimulated with LPS, the peak of TNF alpha activity appeared at 4 hr and then declined. TNF alpha-binding sites on the cell membrane were down-regulated within 1 hr after PMA and LPS treatment and then reappeared 12 hr later. Fifty-five-kilodalton TNF-R mRNA expression during this time period did not correlate with the level of membrane TNF-binding site expression. Additional studies indicated the presence of a 30-kDa TNF-BF in the supernatants which appeared after 24 hr. These data suggest that activated THP-1 and HL-60 cells are capable of releasing TNF-BF into the supernatant and this material may be involved in the control of secreted TNF alpha activities.
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PMID:The regulation of TNF receptor mRNA synthesis, membrane expression, and release by PMA- and LPS-stimulated human monocytic THP-1 cells in vitro. 165 85

Binding of tumor necrosis factor-alpha (TNF-alpha) to its receptor on U937 cells results in rapid and TNF dose-dependent phosphorylation of a cytosolic protein with an apparent molecular mass of 26,000 kDa (p26) and an isoelectric point of 5.6. Half-maximal phosphorylation of p26 was achieved at concentrations of 1.8 ng/ml and was detectable within 20 s of TNF-alpha treatment. p26 is phosphorylated exclusively at serine residues. p26 phosphorylation occurs at 37 degrees C as well as at 14 degrees C, indicating that internalization of the TNF receptor is not required for serine kinase activation. Dephosphorylation of p26 starts 10 min after TNF-induced phosphorylation, suggesting a possible regulatory function of this cytosolic protein within the post-TNF receptor signaling system. p26 is also phosphorylated upon treatment with lymphotoxin. In contrast, both interferon-gamma and lipopolysaccharide fail to induce p26 phosphorylation. Whereas phosphorylated p26 was detected in the TNF-sensitive breast cancer cell line CRL1500, other TNF-responsive tumor cell lines investigated lacked enhanced phosphorylation of p26 in response to TNF, indicating that the 26-kDa phosphoprotein (pp26) may be a cell type-specific second messenger molecule involved in TNF signal transduction in some, but not all, target cells. p26 is also phosphorylated in a subclone of U937 (U937.C27) that responds to TNF-alpha with differentiation, yet is resistant to TNF-alpha-mediated growth inhibition. In contrast, p26 is not phosphorylated in another U937 derivative (U937.G3) that is resistant to both TNF-alpha-induced growth arrest and differentiation, suggesting that pp26 may play a role in the TNF signaling pathway linked to differentiation processes rather than to growth control.
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PMID:Tumor necrosis factor signal transduction. Tissue-specific serine phosphorylation of a 26-kDa cytosolic protein. 253 51

Stimulation with lipopolysaccharide (LPS) will lead to the expression of a variety of genes in CD14+ monocytes/macrophages, but also in CD14- fibroblasts and endothelial cells. Upon secondary LPS stimulation, the expression of many of these genes is only minimal. This applies to several cytokines, most prominent among them tumor necrosis factor (TNF). Induction of tolerance appears to require some degree of activation in the primary exposure, as partial structures of LPS induce tolerance, as long as they are able to activate cells. Studies on the mechanism of unresponsiveness in tolerant cells show that the CD14 LPS receptor is not downregulated but may even increase in number at the cell surface. Furthermore, this receptor appears to be functional in that mobilization of the transcription factor NF-kappa B does still occur. This NF-kappa B complex is composed primarily of p50p50 homodimers, that bind to the respective DNA motif in the promoter region of many proinflammatory genes, thereby blocking transactivation. However, LPS tolerance does not lead to downregulation of all kinds of response, as some genes are even increased in expression upon secondary stimulation; these include p50 of NF-kappa B, TNF receptor type II and interleukin-10 (IL-10). These gene products are involved in the downregulation of proinflammatory cytokines and may thereby be instrumental in the unresponsiveness observed. Hence, tolerance to LPS is not a passive process that occurs in an exhausted cell; rather, it is a well-controlled active response that is orchestrated in order to prevent excessive inflammation. Important modulators of tolerance are glucocorticoids, which result in a general decrease of gene expression, and interferon-gamma (IFN-gamma), which enhances expression of proinflammatory genes. LPS tolerance does occur in some clinical settings, as in hemodialysis, in sepsis and in patients treated repeatedly with LPS or other monocyte activators. In fact, LPS tolerance may be exploited for prophylaxis of severe sepsis in patients at risk.
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PMID:Molecular mechanism in tolerance to lipopolysaccharide. 758 50

Mice bearing a transgene coding for a soluble tumor necrosis factor receptor type 1 (TNFR1)-FcIgG3 fusion protein and placed under the control of the alpha-1-antitrypsin gene promoter were generated. Depending on the mouse line, blood levels of the protein ranged from 25 ng/ml to over 100 micrograms/ml; this level of expression was most often transmitted to the transgene-bearing progeny as a relatively stable feature. High-expressor mice were completely resistant to lipopolysaccharide-induced shock and lethality, including after D-galactosamine sensitization, and mice expressing about 1 microgram of the fusion protein/ml were partially (60%) protected. In contrast, mice expressing less than 0.1 microgram of the protein/ml were more sensitive than controls with respect to incidence and time of death, even though the biological activity of serum tumor necrosis factor (TNF) was partially neutralized. High-expressor mice of the adequate genetic background were markedly, although not completely, protected from death by cerebral malaria after injection with Plasmodium berghei. They were highly susceptible to Listeria monocytogenes, dying from bacterial dissemination after sublethal infection, and to Leishmania major, displaying severe, non-healing lesions after local infection. Under the same conditions, mice expressing about 1 microgram protein/ml were only partially sensitive to these last agents, compared to non-transgenic littermate mice which were fully resistant. These transgenic mice represent a model of permanent, complete or partial, impairment of TNF use, which compares favorably, for ease of breeding and for the range of effects, to mice bearing gene disruptions.
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PMID:Transgenic mice expressing high levels of soluble TNF-R1 fusion protein are protected from lethal septic shock and cerebral malaria, and are highly sensitive to Listeria monocytogenes and Leishmania major infections. 766 2

Numerous lipid A analogs have been synthesized in an attempt to dissociate endotoxic activities from beneficial immunomodulatory activities. In the present study, we have evaluated select lipid A analogs in macrophages for their ability to induce a panel of lipopolysaccharide (LPS)-inducible genes to gain insights into the molecular mechanisms which underlie endotoxicity. We evaluated three monosaccharide lipid A analogs: SDZ MRL 953, an agonist with an improved therapeutic margin over endotoxin; SDZ 281.288, a more toxic analog; and SDZ 880.431, an analog with proven LPS-inhibitory activity. In addition, three disaccharide lipid A analogs (i.e., lipid IVA, SDZ 880.611, and SDZ 880.924) that differ in acylation and phosphorylation patterns were also examined and compared with synthetic lipid A. With the exception of SDZ 880.431, each of these structurally diverse analogs was able to induce the complete panel of LPS-inducible genes, specifically genes which encode tumor necrosis factor alpha (TNF-alpha), interleukin-1 beta, 75-kDa type 2 TNF receptor (D7), IP-10, D3, and D8. These results underscore that macrophage stimulation by lipid A analogs is permissive to considerable structural diversity. Structures with favorable therapeutic indices (SDZ MRL 953, SDZ 880.611, and SDZ 880.924) were not different from structures with poor therapeutic indices (lipid A, lipid IVA, and SDZ 281.288) with regard to gene induction. Nonetheless, the nontoxic SDZ MRL 953 was approximately 1,000-fold less potent than synthetic lipid A at inducing TNF-alpha secretion, and perhaps this contributes to the lack of toxicity exhibited by this compound. The ability of compound SDZ 880.431 to inhibit TNF-alpha secretion induced by both SDZ MRL 953 and smooth LPS suggests that the monosaccharide and smooth LPS share a receptor or a portion thereof. A pattern of protein tyrosine phosphorylation similar to that induced by LPS was stimulated by the monosaccharide SDZ MRL 953 and SDZ 281.288 and disaccharides lipid IVA, SDZ 880.924, and SDZ 880.611, providing evidence for a common signalling pathway.
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PMID:Induction of early gene expression in murine macrophages by synthetic lipid A analogs with differing endotoxic potentials. 768 1

In order to analyse the physiological relevance of the 55 kDa tumor necrosis factor receptor 1 (TNFR1) and its role in various TNF related pathological conditions, such as septic shock, we have generated mice by gene targeting deficient for TNFR1 expression. The TNFR1-deficient mice are unable to cope with Listeria monocytogenes infections but mount an apparently normal immune response when challenged with Vaccinia or LCMV viruses. They are resistant to the lethal effects of lipopolysaccharide (LPS) after sensitization with D-galactosamine (D-GalN) but remain sensitive to very high doses of LPS given alone. We have analyzed functions relevant to inflammatory processes, such as adhesion, secondary factor release, and proliferation in fibroblasts derived from these mice. We show that the TNFR1 virtually monopolises TNF-mediated signaling in all these situations and that the 75 kDa TNFR2 seems to be largely restricted to an accessory role, which is compatible with the previously established "ligand passing" hypothesis.
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PMID:Phenotypic analysis of TNFR1-deficient mice and characterization of TNFR1-deficient fibroblasts in vitro. 774

Anticytokine therapies have been promulgated in gram-negative sepsis as a means of preventing or neutralizing excessive production of proinflammatory cytokines. However, systemic administration of cytokine inhibitors is an inefficient means of targeting excessive production in individual tissue compartments. In the present study, human gene transfer was used to deliver to organs of the reticuloendothelial system antagonists that either inhibit tumor necrosis factor-alpha (TNF-alpha) synthesis or block its interactions with cellular receptors. Mice were treated intraperitoneally with cationic liposomes containing 200 micrograms of either a pCMV (cytomegalovirus)/p55 expression plasmid that contains the extracellular domain and transmembrane region of the human p55 TNF receptor, or a pcD-SR-alpha/hIL-10 expression plasmid containing the DNA for human interleukin 10. 48 h later, mice were challenged with lipopolysaccharide (LPS) and D-galactosamine. Pretreatment of mice with p55 or IL-10 cDNA-liposome complexes improved survival (p < 0.01) to LPS-D-galactosamine. In additional studies, intratracheal administration of IL-10 DNA-liposome complexes 48 h before an intratracheal LPS challenge reduced pulmonary TNF-alpha levels by 62% and decreased neutrophil infiltration in the lung by 55% as measured by myeloperoxidase activity (both p < 0.05). Gene transfer with cytokine inhibitors is a promising option for the treatment of both the systemic and local sequelae of septic shock.
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PMID:Human tumor necrosis factor receptor (p55) and interleukin 10 gene transfer in the mouse reduces mortality to lethal endotoxemia and also attenuates local inflammatory responses. 776 15

A replication-deficient recombinant adenovirus encoding a chimeric protein capable of binding tumor necrosis factor (TNF) and lymphotoxin was given to mice. Administration of this virus (10(9) pfu intravenously) yielded high levels of the recombinant protein in plasma and afforded significant protection to a lethal challenge with lipopolysaccharide with or without D-galactosamine. However, this protein inhibitor was readily detectable in the lung and was associated with decreased neutrophil recruitment and bacterial killing after intratracheal LPS or Pseudomonas aeruginosa, respectively. These data reflect the dual role of many proinflammatory cytokines. This model of TNF inhibition is similar to the homozygous 55-kDa TNF receptor deletion; thus, adenovirus-mediated gene transfer of cytokine inhibitors in vivo is a useful tool to abrogate the function of single or multiple cytokines for investigational or therapeutic purposes.
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PMID:Adenovirus-mediated blockade of tumor necrosis factor in mice protects against endotoxic shock yet impairs pulmonary host defense. 787 3


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