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)

We have studied the interaction of the polycationic peptide antibiotic polymyxin B (PMB) with asymmetric planar bilayer membranes via electrical measurements. The bilayers were of different compositions, including those of the lipid matrices of the outer membranes of various species of Gram-negative bacteria. One leaflet, representing the bacterial inner leaflet, consisted of a phospholipid mixture (PL; phosphatidylethanolamine, -glycerol, and diphosphatidylglycerol in a molar ratio of 81:17:2). The other (outer) leaflet consisted either of lipopolysaccharide (LPS) from deep rough mutants of PMB-sensitive (Escherichia coli F515) or -resistant strains (Proteus mirabilis R45), glycosphingolipid (GSL-1) from Sphingomonas paucimobilis IAM 12576, or phospholipids (phosphatidylglycerol, diphytanoyl-phosphatidylcholine). In all membrane systems, the addition of PMB to the outer leaflet led to the induction of current fluctuations due to transient membrane lesions. The minimal PMB concentration required for the induction of the lesions and their size correlated with the charge of the lipid molecules. In the membrane system resembling the lipid matrix of a PMB-sensitive strain (F515 LPS/PL), the diameters of the lesions were large enough (d = 2.4 nm +/- 8%) to allow PMB molecules to permeate (self-promoted transport), but in all other systems they were too small. A comparison of these phenomena with membrane effects induced by detergents (dodecyltriphenylphosphonium bromide, dodecyltrimethylammonium bromide, sodiumdodecylsulfate) revealed a detergent-like mechanism of the PMB-membrane interaction.
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PMID:Molecular mechanisms of polymyxin B-membrane interactions: direct correlation between surface charge density and self-promoted transport. 953 6

We show that lipopolysaccharide-free actetylated low-density lipoprotein (LDL), but not native LDL, stimulates tumor-necrosis factor-alpha (TNF-alpha) secretion by rat peritoneal macrophages and the signal-transduction pathways involved. The role of the scavenger receptor (SR) in this response was suggested by the absence of an effect induced by native LDL, signal coupling involving pertussis-toxin-dependent guanine-nucleotide-binding regulatory (G) protein, and the complete inhibition of this response by SR ligands [poly(I) and dextran sulfate]. Acetylated LDL induces rapid Ca2+ release from inositol-phosphate-sensitive Ca2+ stores mediated by pertussis-sensitive G proteins and a sustained Ca2+ rise mediated by Ca2+ influx and by Ca2+ release from ryanodine-sensitive Ca2+ stores. Acetylated LDL-induced Ca2+ influx and TNF-alpha production were abolished by inhibitors of phospholipase C (U73122) and phospholipase A2 (bromophenacyl bromide), but were not affected by an inhibitor of protein kinase C (calphostine C). Therefore, Ca2+ influx induced by acetylated LDL is dependent on Ca2+ store depletion. Arachidonate released by acetylated LDL acts as a second messenger to activate TNF-alpha secretion via Ca2+ influx. While the Ca2+ signal was not modified by an inhibitor of protein tyrosine kinases (PTK; herbimycin A), this inhibitor completely blocked TNF-alpha production, suggesting the involvement of PTK downstream of the Ca2+ signal. These results suggest that a sustained elevation of intracellular Ca2+, mediated through Ca2+ influx via the phospholipase-A2-dependent pathway, is essential for induction of TNF-alpha secretion. The type of SR class involved in these pathways remains to be identified.
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PMID:Involvement of calcium and arachidonate metabolism in acetylated-low-density-lipoprotein-stimulated tumor-necrosis-factor-alpha production by rat peritoneal macrophages. 957 94

Here we investigate the effects of tetracycline base and of a semi-synthetic tetracycline derivative, doxycycline, on the induction of inducible nitric oxide synthase and, hence, on the production of nitric oxide (NO) by lipopolysaccharide in J774 macrophage cultured in vitro. The treatment of J774 line with tetracycline base (6.25-250 microM) or doxycycline (5-50 microM) dose-dependently decreased the lipopolysaccharide-stimulated (1 microg/ml) inducible NO synthase activity and, consequently, nitrite formation. For instance, the inhibition was 70% for tetracycline base at 250 microM and 68% for doxycycline at 50 microM. The inhibitory effect of tetracyclines was due neither to a reduction in the viability of the cells, studied as colorimetric 3-[4,5-dimethylthiazol-2yl]-2,5-diphenyltetrazolium bromide (MTT) reduction assay, nor to an indiscriminate inhibition of total protein synthesis, but to a specific decrease in inducible NO synthase protein content in the cells, as attested by the significant reduction of the expression of inducible NO synthase, assayed by sodium-dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) and Western blot. However, no effect of tetracyclines on inducible NO synthase mRNA accumulation could be demonstrated in lipopolysaccharide-stimulated macrophage line, suggesting that the inhibitory effect of tetracyclines on NO synthesis involves post-transcriptional events. The reduction in lipopolysaccharide-stimulated nitrite accumulation produced by tetracyclines was significantly less when they were applied 6 h after lipopolysaccharide and absent 12 h after lipopolysaccharide, indicating that tetracyclines modify an early event in inducible NO synthase activation operating after mRNA transcription. The findings presented in this study indicate that the modulation of NO synthesis is another possible pathway by which tetracyclines may function as anti-inflammatory compounds.
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PMID:Tetracycline inhibits the nitric oxide synthase activity induced by endotoxin in cultured murine macrophages. 965 71

Antibiotics have previously been shown to have immunomodulatory effects. We examined the effect of the broad-spectrum fluoroquinoline antibiotic trovafloxacin on cytokine synthesis by monocytes obtained from healthy human volunteers and stimulated with either lipopolysaccharide or gram-positive cells (heat-killed Staphylococcus aureus [Pansorbin]). Trovafloxacin levels achievable in humans suppressed in vitro synthesis of each of the cytokines analyzed, viz., interleukin-1 alpha (IL-1 alpha), IL-1 beta, IL-6, IL-10, granulocyte-macrophage colony-stimulating factor, and tumor necrosis factor alpha. This effect was not due to direct effects of the drug on cellular viability; at these concentrations, trovafloxacin did not have demonstrable cytotoxicity for the monocytes, as determined by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide (MTT) assay. Although similar patterns of suppression of cytokine synthesis were observed in samples obtained from the same volunteers on different days, there were significant day-to-day variations. These results reveal that trovafloxacin possesses significant immunomodulatory activity in vitro and suggest that suppression of acute-phase inflammatory responses may occur in vivo, elicited through trovafloxacin's effect on cytokine synthesis by human monocytes.
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PMID:Effect of trovafloxacin on production of cytokines by human monocytes. 966 Oct 9

The interaction of lipopolysaccharide isolated from Klebsiella O3 strain with cationic and cationic-nonionic mixed surfactants has been studied by turbidimetry and by spectrophotometric, spectrofluorometric, viscosity, and conductance measurements. The cationic surfactants benzyldimethyl-n-hexadecylammonium chloride (BDHAC), cetyltrimethylammonium bromide (CTAB), cetylpyridinium chloride (CpCl), dodecylpyridinium chloride (DpCl), and nonionic surfactants polyoxyethylene glycol-tert-octylphenyl ether (Triton X-100), polyoxyethylenesorbitan monolaurate (Tween-20), and polyoxyethylene (23) lauryl ether (Brij-35) were used in all the experiments as single surfactants and also as mixed surfactants of different compositions. Mixed surfactants were found to be more effective in binding with the lipopolysaccharide molecules. Micellar effects of cationic and cationic-nonionic mixed surfactants on binding with the anionic polymer are presented in this paper. The binding was found to be electrostatic in origin and also hydrophobic in nature to a certain extent. Copyright 1998 Academic Press.
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PMID:Interaction of Mixed Surfactants with Bacterial Lipopolysaccharide. 970 63

Since there is increasing evidence that nitric oxide (NO) plays a crucial role in the pathogenesis of inflammatory diseases, this study was undertaken to address whether the methanol (MeOH) extract and its fractions of the bark of Ulmus davidiana Planch (Ulmaceae) could modulate the expression of inducible NO synthase (iNOS) in thioglycollate-elicited murine peritoneal macrophages and murine macrophage cell line, RAW264.7 cells. Stimulation of the peritoneal macrophages and RAW264.7 cells with interferon-gamma (IFN-gamma) and lipopolysaccharide (LPS) resulted in increased production of NO in the medium. However, the butanol (BuOH) fraction of the MeOH extract of U. davidiana barks showed marked inhibition of NO synthesis in a dose-dependent manner. The inhibition of NO synthesis was reflected in the decreased amount of iNOS protein, as determined by Western blotting. The BuOH fraction did not affect the viability of RAW264.7 cells, as assessed by methylthiazol-2-yl-2, 5-diphenyl tetrazolium bromide (MTT) assay; rather, it reduced endogenous NO-induced apoptotic cell death via inhibition of NO synthesis in RAW264.7 cells. On the other hand, the BuOH fraction showed no inhibitory effect on the synthesis of NO by RAW264.7 cells, when iNOS was already expressed by the stimulation with IFN-gamma and LPS. Collectively, these results demonstrate that the BuOH fraction inhibits NO synthesis by inhibition of the induction of iNOS in murine macrophages.
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PMID:Inhibition of nitric oxide synthesis by butanol fraction of the methanol extract of Ulmus davidiana in murine macrophages. 974 85

We determined the MICs of ampicillin, ciprofloxacin, erythromycin, imipenem, and rifampin for two clinical isolates of Legionella pneumophila serogroup 1 by 3-(4,5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) reduction assay and by quantitative culture. To test the influence of subinhibitory concentrations (sub-MICs) of antimicrobial agents on Legionella uptake into Acanthamoeba castellanii and U937 macrophage-like cells, both strains were pretreated with 0.25 MICs of the antibiotics for 24 h. In comparison to that for the untreated control, subinhibitory concentrations of antibiotics significantly reduced Legionella uptake into the host cells. Measurement of the binding of monoclonal antibodies against several Legionella antigens by enzyme-linked immunoassays indicated that sub-MIC antibiotic treatment reduced the expression of the macrophage infectivity potentiator protein (Mip), the Hsp 60 protein, the outer membrane protein (OmpM), an as-yet-uncharacterized protein of 55 kDa, and a few lipopolysaccharide (LPS) epitopes. In contrast, the expression of some LPS epitopes recognized by monoclonal antibodies 8/5 and 30/4 as well as a 45-kDa protein, a 58-kDa protein, and the major outer membrane protein (OmpS) remained unaffected.
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PMID:Subinhibitory concentrations of antimicrobial agents reduce the uptake of Legionella pneumophila into Acanthamoeba castellanii and U937 cells by altering the expression of virulence-associated antigens. 979 18

The mechanisms used by Haemophilus somnus to survive and multiply within bovine mononuclear phagocytes are not fully understood. In order to study the interaction between bovine mononuclear phagocytes and H. somnus, a colorimetric assay using 3-(4, 5-dimethylthiazol-2-yl)-2,5-diphenylItetrazolium bromide (MTT) was developed to assess the survival of H. somnus within cultured bovine blood monocytes (BBM). Using this system, it was found that H. somnus was able to survive within BMM in vitro, and the kinetics of its survival were similar to that seen in BBM isolated from experimentally infected cattle. Using ultrastructural studies, it was possible to demonstrate the survival of H. somnus in freshly isolated bovine mononuclear phagocytes in membrane-bound vacuoles. To determine if activation of macrophage function would result in elimination of intracellular H. somnus, BBM were treated with E. coli lipopolysaccharide (LPS) or recombinant bovine (rBo) cytokines, interferon-gamma (IFN-gamma), granulocyte macrophage colony stimulating factor (GM-CSF), tumour necrosis factor-alpha (TNF-alpha) or interleukin-1beta (IL-1beta). Treatment of BBM with rBoIFN-gamma, rBoGM-CSF or E. coli LPS resulted in decreased intracellular survival of H. somnus at 18 and 48 h, whereas BBM treated with rBoTNF-alpha or rBoIL-1beta had reduced intracellular survival of H. somnus only at 18 h. However, none of these treatments resulted in complete elimination of the intracellular bacteria. The ability of H. somnus to survive and multiply in both freshly isolated and cytokine-treated cultured BBM demonstrated the capability of H. somnus to escape from macrophage killing mechanisms. This capability may play a role in the dissemination of H. somnus infection in the body.
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PMID:Intracellular survival of Haemophilus somnus in bovine blood monocytes and alveolar macrophages. 987 52

Since nitric oxide (NO) was recognized as a potent microbicidal agent, its role in host defence against intracellular parasites has been widely demonstrated. Recent evidence suggests a role for NO in combating extracellular and multicellular pathogens. This defence activity has been demonstrated toward the larvae of Schistosoma mansoni, microfilariae of Onchocerca linealis, several stages of Brugia malayi and protoscoleces of Echinococcus multilocularis. Many parasites suppress Th1 lymphocytes and directly inhibit NO production by inducing cytokines, such as IL-4, IL-10 and TGF-beta. In this study, we have investigated the effects of Anisakis simplex, an enhancer of Th2-dominant responses, on NO production. We studied the effect of crude extracts (CE) and excretory-secretory (ES) products on the induction of inducible nitric oxide synthase (iNOS) in bacterial lipopolysaccharide (LPS)-treated J774 macrophages. Stimulation of macrophages by LPS (1 microg/ml) increased nitrite concentrations in the culture medium at 24 h. Co-administration of A. simplex products with LPS, dose-dependently reduced the accumulation of nitrite. Nitrite production is due to induction of iNOS, and both L-NAME (N(G)-nitro-L-arginine methyl ester) (50 microM) and dexamethasone (10 microM) inhibited nitrite accumulation (54.2 and 92.1% inhibition, respectively). The inhibition of nitrite production by A. simplex was 42.1-97.8% in the range 4.75-76 microg/well (CE products) and 37.2-61.5% in the range 5-20 microg/well (ES products). Cell viability assayed by the mitochondrial-dependent reduction of MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) verified that the inhibition was not due to general cellular toxicity. However, the effects of A. simplex, were reduced when NOS had been induced by prior exposure to LPS and any possible further induction was blocked by cycloheximide, an inhibitor of protein synthesis.
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PMID:Effects of Anisakis simplex on nitric oxide production in J774 macrophages. 1022 90

Cyclooxygenase (COX) converts arachidonic acid to prostaglandin (PG) H2, which is further metabolized to various prostaglandins, prostacyclin and thromboxane A2. COX exists in at least two different isoforms. COX-1 is constitutively expressed, whereas COX-2 is induced by proinflammatory stimuli. Prostaglandin E2 is a major metabolite of COX activation. In order to compare the activity of target ligands and COX inhibitors on PGE2 synthesis and release, the responsiveness of several cell lines to the calcium ionophore A23187, bacterial lipopolysaccharide (LPS), nonsteroidal anti-inflammatory drugs (NSAIDs), and the glucocorticoid, dexamethasone, were investigated. For intracellular measurements, the culture supernatant was aspirated, and the cells were thoroughly washed and lysed with dodecyltrimethylammonium bromide. Intracellular and secreted PGE2 were measured with an enzyme immunoassay. A23187 and LPS increased intracellular PGE2 in a dose-dependent manner. Kinetic experiments with A23187-stimulated mouse 3T3 fibroblast cells revealed a distinct biphasic response in COX activity. In the presence of NSAIDs or dexamethasone, there was a dose-dependent inhibition in intracellular PGE2 with A23187-stimulated 3T3 cells. Inhibitory studies demonstrated an apparent increased sensitivity of COX activity to the action of inhibitors when measuring intracellular PGE2 compared with using cell culture supernatants. Indeed, intracellular PGE2 levels were comprehensively reduced in the presence of low concentrations of inhibitor. The utilization of cell culture lysates and, in particular, measurement of intracellular PGE2 should prove useful for identifying new COX inhibitors.
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PMID:Intracellular measurement of prostaglandin E2: effect of anti-inflammatory drugs on cyclooxygenase activity and prostanoid expression. 1036 Oct


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