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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 role of cyclic adenosine 3':5' monophosphate (cAMP) in the regulation of lipopolysaccharide (LPS)-induced tumour necrosis factor (TNF) production by mouse peritoneal macrophages. LPS did not alter the intracellular levels of cAMP. However, prostaglandin E2 (PGE2) and cholera toxin, both of which are known to increase intracellular levels of cAMP, consistently inhibited LPS-induced TNF production. The cAMP analogues, dibutyryl cAMP (DbcAMP) and 8-bromo cAMP (8BrcAMP), also inhibited TNF production, whereas pertussis toxin, which inactivates the inhibitory guanine nucleotide-binding protein (Gi), had no effect. These observations suggested that LPS did not itself modify macrophage adenylate cyclase activity, while agents that increased intracellular cAMP levels were able to inhibit LPS-induced macrophage TNF production.
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PMID:Regulation of tumour necrosis factor production by mouse peritoneal macrophages: the role of cellular cyclic AMP. 284 58

The effect of secreted virulence components of Bordetella pertussis on chemiluminescence (CL) of rabbit peritoneal neutrophils was determined with the chemotactic peptide N'-formyl-L-methionyl-L-leucyl-L-phenylalanine (fMLP) or intact B. pertussis as the stimulus. Pertussis toxin (PT) inhibited the response to fMLP in a dose-dependent manner, although only after the neutrophils had been exposed to the toxin for greater than 15 min. Both filamentous haemagglutinin (FHA) and lipopolysaccharide (LPS) markedly enhanced the CL response to fMLP after greater than or equal to 15 min incubation with the neutrophils. Similar effects to those of B. pertussis LPS were also seen with smooth and rough LPS from Salmonella minnesota. With the lowest dose of each component which elicited a maximal effect on CL, the inhibitory effect of PT overrode the enhancing effect of FHA and B. pertussis LPS. Pre-incubation of neutrophils with PT, FHA or B. pertussis LPS caused a slight reduction in the subsequent CL response to virulent B. pertussis Tohama. Virulent (phase I, or X-mode) organisms of B. pertussis 18334 and B. pertussis Tohama induced greater neutrophil CL than their avirulent (C-mode) derivatives. There appeared to be an inverse correlation between bacterial hydrophilicity and the ability to induce neutrophil CL: X-mode bacteria were significantly less hydrophilic than C-mode organisms. Three mutants, the adenylate cyclase (AC)- and haemolysin (HLY)-deficient B. pertussis BP348, the FHA-deficient B. pertussis BP353, and the PT-deficient B. pertussis BP357, generated similar levels of CL and had similar hydrophilicity values. The hydrophilicity value of the avirulent mutant B. pertussis BP347 (deficient in AC, HLY, FHA and PT) and the CL induced by this strain were similar to those of B. pertussis C-mode organisms. Thus, the interaction of B. pertussis with neutrophils appears to be complex, reflecting both the alteration of leucocyte function by secreted virulence components of the organism and, in the absence of opsonins, the surface properties of the bacterium.
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PMID:Interaction of Bordetella pertussis virulence components with neutrophils: effect on chemiluminescence induced by a chemotactic peptide and by intact bacteria. 290 18

Lipopolysaccharide, a component of the outer membrane of Gram-negative bacteria, activates B lymphocytes and macrophages. Pertussis toxin, which inactivates several members of the G protein family of signaling components, including Gi and transducin, was found to inhibit the lipopolysaccharide-induced responses of the WEHI-231 B lymphoma cell line and the P388D1 macrophage cell line. These results, combined with the demonstration that lipopolysaccharide inhibits adenylate cyclase activity in P388D1 cells, strongly argues that lipopolysaccharide activation of cells is mediated by a Gi-like receptor-effector coupling protein.
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PMID:Pertussis toxin inhibition of B cell and macrophage responses to bacterial lipopolysaccharide. 309 21

Many bacterial toxins are proteins, encoded by the bacterial chromosomal genes, plasmids or phages. Lysogenic phages form part of the chromosome. The toxins are usually liberated from the organism by lysis, but some are shed with outer membrane proteins in outer membrane vesicles. An important non-protein toxin is lipopolysaccharide or endotoxin, which is a constituent of the cell wall of gram negative bacteria. Toxins may damage the eukaryotic cell membrane by combining with some structural component, or otherwise alter its function. Many toxins combine with specific receptors on the surface membrane, frequently glycoproteins or gangliosides, and penetrate the cell to reach their intracellular target. A common mechanism of entry is absorptive endocytosis. Many protein toxins have an A-B structure, B being a polypeptide which binds to the receptor and A being an enzyme. Many toxins are activated, either when produced by the bacterium or when bound to the membrane receptor, by proteases (nicking). An enzymatic process common to many toxins is adenosine diphosphate (ADP)-ribosylation of the adenylate cyclase regulatory proteins, leading to an increase in intracellular cyclic adenosine monophosphate (cAMP). This is the mechanism of action of cholera toxin. Diphtheria toxin catalyzes the transfer of ADP-ribose to elongation factor-2, inhibiting protein synthesis. Most toxins act on the target cells to which they bind, but tetanus toxin, and, to a lesser degree, botulinum toxin, ascend axons and affect more distant structures. Although many toxin effects caused by bacteria have been described, only a few toxins have been identified, characterized, and their mode of action determined at the molecular level. The best known of these are discussed.
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PMID:Bacterial toxins. 328 62

Stimulant action of the mitogenic polyanion, polyacrylic acid (PAA) was investigated in mouse lymphocyte culture in vitro. B cell division was induced by "impulsive" PAA treatment. Shortly after PAA treatment the activity of the membrane enzymes, adenylate and guanylate cyclases, was assayed according to the changes in the concentration of cAMP and cGMP. The effect of PAA on the time course of cAMP and cGMP in lymphocytes was compared to the effect of B cell mitogen of other chemical nature--bacterial lipopolysaccharide (LPS). PAA was demonstrated to produce no effect on the activity of membrane cyclase enzymes. On the contrary, following LPS addition guanylate cyclase in the lymphocyte membrane was activated within the first 5-10 minutes. Later on (after 2h) the cells activated with LPS showed an increase in adenylate cyclase activity. By the 12th-24th hour the concentration of cAMP in the LPS-stimulated cells reached 250% of the control level. The differences are discussed between the mitogenic polyanion (PAA) and the lipid-modifying mitogen (LPS) in the molecular mechanisms by which the lymphocyte responses are activated.
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PMID:[Analysis of the cyclase enzyme activity of the cell membrane following lymphocyte stimulation with a mitogenic polyanion]. 614 37

The lipopolysaccharide (LPS)-nonresponder mouse strains C3H/HeJ, C57BL/10ScCR and C57BL/10ScN do not respond to LPS acting as a polyclonal B-cell activator, a mitogen, or an adjuvant. The genetic basis for the defective LPS response has been extensive studied in C3H/HeJ and C57BL/10ScCR mice, in which it was demonstrated that a single gene locus on chromosome 4 was responsible for LPS unresponsiveness. Lithium chloride, a potent inhibitor of adenylate cyclase, not only improved lymphocyte activity in a patient with adenosine deaminase deficiency but also enhanced the phytohaemagglutinin (PHA)-induced responses of normal human lymphocytes. Therefore, we investigated whether LiCl could restore LPS responsiveness in spleen cells of C3H/HeJ mice. We show here that LPS, in the presence of LiCl, induced polyclonal IgM and IgG antibody formation and DNA synthesis in C3H/HeJ mouse spleen cells in vitro. Moreover, LiCl (10 mM), which by itself is non-mitogenic, increased RNA synthesis in spleen cells from both LPS-nonresponder and high responders strains; in contrast, LPS failed to increase RNA synthesis in cells from such LPS-nonresponder strains as C3H/HeJ and B10ScCr mice.
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PMID:Lithium chloride induces partial responsiveness to LPS in nonresponder B cells. 618 Mar 27

Kupffer cells exposed to bacterial lipopolysaccharide in vitro synthesized collagenase and released the major portion of it into the extracellular space while the intracellular level of enzyme was not altered significantly. Cycloheximide prevented the appearance of collagenase in the medium indicating de novo synthesis. Indomethacin, an inhibitor of cyclooxygenase, also blocked collagenase synthesis. In line with this observation. Kupffer cells were found to synthesize substantial amounts of prostaglandin E2 when exposed to lipopolysaccharide; concomitantly, cellular cAMP levels were increased. Indomethacin was shown to abolish the stimulated cAMP formation. Addition to the culture medium of cAMP or dibutyryladenosine 3', 5'-monophosphate as well as of prostaglandin E2 or, to a lesser extent, prostaglandin E1 allowed indomethacin-inhibited cells to resume the production of collagenase. It is proposed that in rat Kupffer cells lipopolysaccharide-elicited collagenase synthesis and excretion is mediated sequentially by stimulated production of prostaglandin E2, enhanced adenylate cyclase activity and increased intracellular cAMP levels.
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PMID:Involvement of prostaglandin E and adenosine 3', 5'-monophosphate in lipopolysaccharide-stimulated collagenase release by rat Kupffer cells. 628 7

Anandamide (arachidonylethanolamide), isolated from the porcine brain, and 2-arachidonyl-glycerol (2-Ara-Gl), derived from the canine gut, are two recently identified putative endogenous cannabinoid receptor ligands. Both ligands have been reported to possess binding affinity for cannabinoid receptor subtypes, CB1 and CB2. The objective of the present studies was to investigate the immunomodulatory effects of both of these ligands in B6C3F1 mouse splenocytes. 2-Ara-Gl produced a marked and dose-related inhibition of the mixed lymphocyte response, anti-CD3 mAb-induced T-cell proliferation and LPS-induced B-cell proliferation, whereas having no inhibitory effect on phorbol-12-myristate-13-acetate/ionomycin-induced cell proliferation. Interestingly, the inhibitory effects by 2-Ara-Gl on proliferation were at least dependent in part on cell density. At high cell density, 2-Ara-Gl enhanced lymphoproliferation whereas exhibiting marked inhibitory activity at low cell density. Similarly, in vitro primary immunoglobulin M antibody-forming cell responses which are dependent on high cell density also were found to be enhanced by 2-Ara-Gl. Conversely, anandamide exhibited no inhibitory effects on cell proliferative responses to stimulation by anti-CD3 mAb, lipopolysaccharide or phorbol-12-myristate-13-acetate/ionomycin treatment. Anandamide also showed no effect on the in vitro sheep erythrocyte antibody-forming cell response. Although shown previously to markedly inhibit forskolin-stimulated cyclic AMP accumulation, 2-Ara-Gl exhibited no effect on basal adenylate cyclase activity in splenocytes. Additionally, anandamide showed negligible inhibitory effects at extremely high concentrations on forskolin-stimulated adenylate cyclase activity and no effect on basal adenylate cyclase activity in splenocytes.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Effects of putative cannabinoid receptor ligands, anandamide and 2-arachidonyl-glycerol, on immune function in B6C3F1 mouse splenocytes. 747 35

The aim of the present study was to determine whether two classical macrophage activators, bacterial lipopolysaccharide (LPS) and interferon-gamma (IFN-gamma) could affect the accumulation of the second messenger cAMP in cultured rat microglia and astrocytes. Purified microglia and astrocyte secondary cultures obtained from the neonatal rat were grown for 3 days in basal medium Eagle (BME) + 10% fetal calf serum (FCS). Exposure of microglia to LPS resulted into a dose- and time-dependent decrease in the accumulation of cAMP induced by receptor-mediated (isoproterenol or prostaglandin E2) or direct (forskolin) activation of adenylate cyclase. The inhibitory effect of LPS was rapid (a 10 min preincubation was sufficient to approach a maximal effect), occurred at low doses (IC50 = 1.2 ng/ml), and was not abrogated by pertussis toxin. A selective inhibitor of type IV phosphodiesterase (rolipram, 100 nM) prevented the effect of LPS on cAMP accumulation, while inhibitors of other forms of phosphodiesterase were unable to do so. IFN-gamma (100 u/ml) also caused a depression of the evoked cAMP accumulation in microglia after a 10 min preincubation, and its effect was prevented by rolipram, as in the case of LPS. Astrocytes differed from microglia in that LPS (1-100 ng/ml) did not inhibit the accumulation of cAMP induced by either isoproterenol or forskolin; on the other hand, IFN-gamma did have an inhibitory effect (though less pronounced than in microglia) that could be prevented by rolipram.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Interferon-gamma and lipopolysaccharide reduce cAMP responses in cultured glial cells: reversal by a type IV phosphodiesterase inhibitor. 755 45

Some physicochemical properties of B.pertussis antigenic complexes isolated from synthetic and semisynthetic culture media have been studied. The chemical composition of these complexes has been determined. Proteins, polypeptide subunits and lipopolysaccharide forming these complexes have been characterized. The presence of two main protective substances of B.pertussis has been revealed: fimbrial hemagglutinin and B.pertussis toxin. The influence of culture medium on the level of the synthesis of B.pertussis adenylate cyclase has been studied.
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PMID:[A comparative analysis of the antigenic complexes isolated from synthetic and semisynthetic media for the cultivation of Bordetella pertussis]. 765 46


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