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PubMed1992

Effect of Helicobacter pylori lipopolysaccharide on the synthesis of sulfated gastric mucin.

The effect of H. pylori lipopolysaccharide on the synthesis and secretion of sulfated mucus glycoprotein in gastric mucosa was investigated. The lipopolysaccharide, while showing no discernible effect on the apomucin synthesis, exerted a profound inhibitory effect on the process of mucus glycoprotein glycosylation and sulfation, and evoked a rapid (within 15 min) inhibition (65%) in both mucin glycosylation and sulfation at its optimal concentration of 100 micrograms/ml. The data on mucin secretory responses indicated that the added lipopolysaccharide caused a 57% stimulation in sulfated mucin secretion within 15 min followed thereafter by inhibition, which reached a maximum of 32% by 45 min. The high molecular weight mucin form predominated in the initial secretion, while prolonged exposure to the lipopolysaccharide caused a significant increase in the low molecular weight mucin form. The results suggest that H. pylori lipopolysaccharide exerts detrimental effect on mucus glycoprotein sulfation and assembly.

Animals↗

PubMed1991

Bacterial lipopolysaccharides alter human endothelial cell morphology in vitro independent of cytokine secretion.

Lipopolysaccharides derived from six bacterial species were found to alter human endothelial cell morphology in vitro in a species-dependent and dose-dependent manner. Lipopolysaccharides derived from Salmonella enteritidis (SeLPS) induced the strongest response, whereas lipopolysaccharides from Vibrio cholerae produced no effect. Cell-shape changes induced by SeLPS (10 micrograms/ml) were noticeable by 24 hours and reached a maximum by 72 hours, thus paralleling the effects produced by the recombinant cytokines interferon gamma (IFN-gamma) (10(3) U/ml), tumor necrosis factor (10(2) U/ml), and interleukin-1 (5 to 10 U/ml). Pretreatment of human endothelial cells with IFN-gamma (10(3) U/ml) for 24 hours induced an accelerated morphologic response to subsequent SeLPS (10 micrograms/ml) stimulation and vice versa, suggesting independent pathways of action. Simultaneous treatment of human endothelial cells with SeLPS and IFN-gamma produced a more rapid onset of morphologic changes and a stronger overall effect. Culture medium containing polymyxin B inhibited cell-shape changes induced by lipopolysaccharides but not those induced by the cytokines. Conditioned medium generated over a 12-hour period following a 24-hour SeLPS/IFN-gamma stimulation did not contain measurable cytokine antigens, nor did it induce biologic responses associated with interleukin-1, IFN-gamma, and tumor necrosis factor alpha. The results indicate that lipopolysaccharides act directly on endothelial cells as well as synergistically with IFN-gamma to alter cell morphology and may, therefore, contribute to the vascular pathology of gram-negative infections.

Bacterial Toxins↗

PubMed1991

Analysis of unmodified endotoxin preparations by 252Cf plasma desorption mass spectrometry. Determination of molecular masses of the constituent native lipopolysaccharides.

Nine unmodified endotoxin preparations constituted of Re-, Rd-, and Rc-type lipopolysaccharides (2 to 5 glycoses), representing four species of enterobacteria were analyzed by 252Cf plasma desorption mass spectrometry. The constituent lipopolysaccharides were characterized by the ion pair: (M-H)- and its corresponding lipid fragment ion. The lipid fragment ion is produced by cleavage of the glycosidic bond of the 3-deoxy-D-manno-oct-2-ulosonic acid unit that substitutes O-6' of the glucosamin beta 1'-6glucosamine ("lipid A backbone") disaccharide of the lipid A moiety. These lipid fragment ions were identical to the (M-H)- ions seen in the spectra of homologous isolated lipid A preparations that were obtained by hydrolysis (pH 4.5, 100 degrees C) promoted by sodium dodecyl sulfate. Since the molecular components present in the endotoxin preparations analyzed are known, the ion pair (M-H)(-)-lipid fragment ion defines the molecular compositions of each individual lipopolysaccharide. Heterogeneity of the R-type endotoxin preparations analyzed was due almost exclusively to differing lipid A moieties. In three Salmonella minnesota 595 Re endotoxin preparations 10 different lipopolysaccharides were identified, only two of which were common to all three preparations. Of the nine lipopolysaccharides identified in two S. minnesota R7 endotoxin preparations, only two were present in both.

Bacterial Toxins↗

PubMed1990

Enhancement of tumour necrosis factor production and sensitivity to interleukin-2 of human peripheral blood mononuclear cells stimulated by lipopolysaccharide and muramyl dipeptide in vitro.

The effect of lipopolysaccharide, muramyl dipeptide, and a combination of these agents in vitro on the production of tumour necrosis factor (TNF) by human peripheral blood mononuclear cells (PBMC; monocytes and lymphocytes) and on the sensitivity of these cells to recombinant interleukin-2 (IL-2) was studied. Both lipopolysaccharide and muramyl dipeptide, alone and combined, induced the production of TNF alpha by blood monocytes and lymphocytes, although the T-cells made only a very small contribution to the TNF produced by the lymphocyte fraction, most being produced by the B-cells. The B-lymphocytes and monocytes also spontaneously produced TNF alpha. Pretreatment of the mononuclear cells with a combination of lipopolysaccharide and muramyl dipeptide, but not with each preparation separately, led to enhancement of the proliferative response of these cells to recombinant IL-2. Incubation of mononuclear cells with muramyl dipeptide, muramyl dipeptide plus lipopolysaccharide, and to a lesser extent with lipopolysaccharide alone led to the generation of more-active lymphokine-activated killer cells in the presence of IL-2 than when IL-2 was used alone. The resultant lymphokine-activated killer cells lysed both human and murine tumour target cells.

Acetylmuramyl-Alanyl-Isoglutamine↗

PubMed1988

Production and partial characterization of monoclonal antibodies to Pasteurella haemolytica A1 capsular polysaccharide and lipopolysaccharide.

Hybridoma-derived monoclonal antibodies (MAB) against the cell surface antigens of Pasteurella haemolytica serotype 1 were obtained by the fusion of murine myeloma cells (P3 X 63 - Ag 8.653) with splenocytes of BALB/c mice immunized with crude logarithmic growth-phase culture supernatant. Initial screening was performed, using an ELISA, with the same bacterial growth culture supernatant as coating antigens. Further selection was done, using a panel of purified antigens--either capsular polysaccharide or lipopolysaccharide--as the coating antigen in an ELISA, and then performing a leukotoxin-neutralization assay. Two MAB, designated IIB-6 and H-2, reacted specifically with the capsular polysaccharide and the other 3, designated IVG-3, IH-3, and IIC-2, reacted with the lipopolysaccharide. One MAB, designated IH-6, did not react with leukotoxin, capsular polysaccharide, or lipopolysaccharide. The MAB to the capsular polysaccharide (IIB-6 and H-2) were characterized further; both antibodies belonged to the IgM class and were agglutinating. In addition, they promoted neutrophil-mediated opsonophagocytosis and complement-mediated immune bacteriolysis of P haemolytica serotype 1. Results from 3 studies indicated that the MAB IIB-6 and H-2 were specific only to the capsular polysaccharide of serotype 1 of P haemolytica. The MAB to the lipopolysaccharide (IVG-3, IH-3, and IIC-2) were of the IgG1, IgG3, and IgM classes, respectively and were not characterized further. The availability of a MAB identifying a serotype-specific, surface-exposed determinant on the capsule of P haemolytica serotype 1 should facilitate and expand studies concerning the role of the capsular material and lipopolysaccharide in the pathogenicity of P haemolytica infection in cattle.

Animals↗

PubMed1986

C3b binding, but not its breakdown, is affected by the structure of the O-antigen polysaccharide in lipopolysaccharide from Salmonellae.

Bacteria whose lipopolysaccharide contains O-antigen side chains activate complement via the alternative pathway. We have shown previously that three strains of Salmonella, differing in the chemical structure of their O-antigens, consumed C3 to different extents when incubated in C4-deficient guinea pig serum. Moreover, sheep erythrocytes coated with lipopolysaccharide purified from these strains mimicked whole cells in C3 consumption, proving that lipopolysaccharide alone could account for these results. We have now measured the deposition of 125I-C3 in this system, and found that C3 deposition parallels C3 consumption in rate and extent, and differs for surfaces bearing different O-antigens, whether tested with bacteria or with erythrocytes coated with purified lipopolysaccharide. We have also examined the fate of C3 on these Salmonellae by measuring the size and quantity of 125I-C3 breakdown fragments by SDS-PAGE, and have determined the kinetics of conversion of C3b to iC3b by using conglutinin, a molecule that binds specifically to iC3b. There is no difference in breakdown of C3b deposited on cells with different O-antigens: all show partial conversion to iC3b and C3dg as indicated by 68,000, 44,000, and 41,000 m.w. bands on reduced SDS gels. Furthermore, for all strains, the Ka of conglutinin binding to iC3b is similar (0.49 to 0.69 X 10(8) M-1), as is the rate of generation of iC3b and the final ratio of iC3b:C3b + iC3b (0.62 to 0.72). We therefore postulate that the fine structure of the O-antigen in lipopolysaccharide determines the magnitude of alternative pathway activation on the bacterial surface by affecting the rate and extent of C3b deposition, but not the rate and extent of breakdown of C3b.

Antigens, Bacterial↗

PubMedDate not supplied

Comparisons of serologic responses of white Leghorn and New Hampshire red chickens to purified lipopolysaccharides of Pasteurella multocida.

White leghorn and New Hampshire red chickens were inoculated with purified lipopolysaccharides of 14 serotypes of Pasteurella multocida to determine their ability to produce serotype-specific antisera for somatic antigen typing. Specific antisera were made by both breeds of chicken to lipopolysaccharides of serotypes 1, 3, 4, 6, 8, and 16. No specific antisera were made against lipopolysaccharides of serotypes 2, 5, 7, 12, and 14. Lipopolysaccharides of serotypes 10 and 11 failed to stimulate antibody production. White leghorns were more responsive than New Hampshire red chickens. White leghorn antisera had higher titers to lipopolysaccharides in passive hemagglutination tests and produced more intense precipitin reactions with heat-stable antigens in the gel-diffusion-precipitin test.

Animals↗

PubMed1982

Inhibitory effect of glucocorticoid on complement activation induced by lipopolysaccharide.

Endotoxic lipopolysaccharide is verified to activate complement, which seems to be one of the major pathogenic processes of septic shock, and glucocorticoid antagonizes this endotoxic manifestation in a dose-related manner. In this study, we tried to elucidate how lipopolysaccharide activates complement in vitro, and how glucocorticoid affects the interaction between them. First, we elucidated in vitro that complement was consumed in proportion to the dose of lipopolysaccharide added. Next we made clear that glucocorticoids inhibit the complement activation by lipopolysaccharide in a dose-related manner in vitro, and the dose that inhibits endotoxic complement activation by 50% was almost the same for hydrocortisone, prednisolone, and dexamethasone. We conclude that lipopolysaccharide activates complement in a dose-related manner and that glucocorticoids inhibit this activation in a dose-related manner, and this may be the main antiendotoxic property of glucocorticoids.

Complement Activation↗

PubMed1975

Fractions of lipopolysaccharide from Escherichia coli O111:B4 prepared by two extraction procedures.

Lipopolysaccharides have been extracted from Escherichia coli O111:B4 by phenol extraction and by a new method employing aqueous butanol. Both methods yield very similar lipopolysaccharide preparations. Gel filtration chromatography of either preparation yields two physically and chemically distinct lipopolysaccharide fractions. One fraction contains lipopolysaccharide molecules with long antigenic side chains. It acts like a highly asymmetric unit with an apparent weight of 1.5 times 10-6 and is not dissociated by detergents or deacylation. The second fraction has a short antigenic side chain and can be dissociated by sodium dodecyl sulfate and Triton X-100 into units of approximately 90,000. Some properties of the lipopolysaccharide fractions vary with the method of extraction.

Butanols↗

PubMed1995

Sucralfate counteracts the inhibition of gastric mucosal mucin receptor by Helicobacter pylori lipopolysaccharide.

BACKGROUND: Among the disturbances in gastric mucosal defense associated with Helicobacter pylori infection is the loss of mucus coat continuity, which results in a severe disturbance in the ability of mucus coat to maintain its functions as the pre-epithelial element of gastric mucosal defense. Here, we show that H. pylori, through its cell-wall lipopolysaccharide, disrupts the interaction between gastric mucin and its mucosal receptor, and that sucralfate is capable of counteracting this untoward effect of the bacterium. METHODS: The receptor was isolated from octylglucoside-solubilized gastric mucosal epithelial cell membranes by affinity chromatography on Sepharose-bound wheat germ agglutinin and following iodination with 125I, used in the binding assays for mucin in the presence of H. pylori lipopolysaccharide and sucralfate. RESULTS: Preincubation of the receptor protein with H. pylori lipopolysaccharide led to a decrease in mucin binding. The inhibitory effect was proportional to the concentration of lipopolysaccharide and reached a maximum of 91% at 30 micrograms/ml. The effect of H. pylori lipopolysaccharide was countered by sucralfate, which caused a dose-dependent relief of the inhibitory effect. The maximum (75%) restoration in mucin-receptor binding occurred at 60 micrograms/ml sucralfate. CONCLUSIONS: The results provide strong evidence for the effectiveness of sucralfate in preventing the loss of gastric mucus coat continuity caused by H. pylori.

Animals↗

PubMedDate not supplied

Inhibition of lipopolysaccharide-induced TNF-alpha production by semisynthetic polymyxin-B conjugated dextran.

During episode of severe endotoxemia, concentrations of both lipopolysaccharide and its lipid A-core subfraction are liberated from gram-negative bacteria and become elevated within the systemic circulation. Lipid-A core is the most homogeneous and physiologically toxic segment of the lipopolysaccharide molecule. Polymyxin-B has profound binding avidity for the lipid A-core subfraction of lipopolysaccharide. The mechanism of this binding avidity involves the development of attractive forces between the cationic groups of polymyxin-B and the anionic groups of the lipid A-core moiety of lipopolysaccharide. Complementary attractive forces include hydrophobic interactions which additionally become established between the octylheptanoyl group of polymyxin-B and the saturated carbon chains of the lipid A-core moiety. This paper describes a method for the semisynthetic production of polymyxin-B conjugated dextran in the form of polymyxin-B.ABH.dextran applying the photoreactive crosslinking reagent azidobenzoyl hydrazide (ABH). Molecular design and development of a semisynthetic technique for the conjugation of polymyxin-B to purified dextran fractions was motivated by the pronounced nephrotoxicity associated with this cationic polypeptide antibiotic. Conjugation of polymyxin-B to a relatively large molecular weight carrier compound would increase the overall size of the complex to a degree sufficient to theoretically reduce clearance through glomerular filtration mechanisms. Attributes of such a large molecular weight polymyxin-B conjugated biopharmaceutical would include diminished levels of nephrotoxicity due to a reduction of renal tubular concentrations and a simultaneous prolongation of its intravascular half-life (t (1/2)) and pharmacokinetic profile. Lipopolysaccharide (LPS) binding avidity of polymyxin-B.ABH.dextran was verified by Dot-Blot analysis in conjunction with the application of fluorescein isothiocyanate conjugated E. coli (0.55:B5) LPS (FITC-LPS). Capacity of polymyxin-B.ABH.dextran conjugates to inhibit in vitro LIP-induced synthesis of tumor necrosis factor-alpha (TNF-alpha) was assessed by the application of a tissue culture based biological assay system capable of detecting cytotoxicity mediated by this potent monokine. Semisynthetic conjugates of polymyxin-B.ABH.dextran conjugates (0.6 microns/mL), thereby providing cytoprotectivity (95%; p < or - 0.001. to WEHI 164 clone 13 cell populations relative to untreated reference controls. Since TNF-alpha is currently believed to be the principal endogenous mediator involved in the host's inflammatory response during episodes of endotoxemia, results from these investigations provide a scientific foundation for warranting the elevation of the in vivo efficacy of large molecular weight semisynthetic polymyxin-B conjugates. Results from these investigations may ultimately lead to the application of semisynthetic polymyxin-B.ABH.dextran as a model for the molecular design of semisynthetic production of alternative biopharmaceutical or pharmaceutical agents possessing prophylactic and/or therapeutic efficacy for the management of severe endotoxemia conditions.

Animals↗

PubMed1998

Brain endothelial cells express cyclooxygenase-2 during lipopolysaccharide-induced fever: light and electron microscopic immunocytochemical studies.

Cyclooxygenase-2 (COX-2), a key enzyme in the biosynthesis of prostaglandins, is induced in brain blood vessels by pyrogens, and its essential role in fever has been hypothesized. In this study, we determined (1) the type of cells that express cyclooxygenase-2 in brain blood vessels of lipopolysaccharide-treated rats, and (2) the precise relationship between the time course of fever and that of cyclooxygenase-2 protein expression in these cells. Five hours after the lipopolysaccharide injection (100 microg/kg, i.p.), cyclooxygenase-2-like immunoreactive cells were found in the parenchymal and subarachnoidal blood vessels. In these blood vessels, the cyclooxygenase-2-like immunoreactivity was restricted to the perinuclear region of the endothelial cells as revealed by a laser confocal microscopy, double-immunofluorescence staining with an endothelial marker, and immunoelectron microscopy. On the other hand, the cyclooxygenase-2-like immunoreactive cells were distinct from microglia or perivascular/meningeal macrophages as revealed by double immunostaining with macrophage/microglia-specific antibodies. Cyclooxygenase-2-like immunoreactive cells were first found at 1.5 hr after the lipopolysaccharide injection, at which time the fever had not been developed. After that, the number of cyclooxygenase-2-like immunoreactive cells and fever followed a similar time course, both being highest at 5 hr after the lipopolysaccharide injection and both returning to the baseline by 24 hr. These results demonstrate that brain endothelial cells are the primary sites where the activation of arachidonic acid cascade takes place during fever after intraperitoneal injection of lipopolysaccharide.

Animals↗

PubMed1997

Pathobiology of lipopolysaccharide.

Lipopolysaccharide is a component of the gram-negative bacterial cell wall that is responsible for 25,000-50,000 deaths in the United States each year. The sequelae of gram-negative infection and septicemia leading to death include fever, hypotension with inadequate tissue perfusion, and disseminated intravascular coagulation. It is clear that different cell types respond differently to lipopolysaccharide. Furthermore, various autacoids and cytokines are released that can affect cellular function even in cell types that do not recognize lipopolysaccharide. Despite advances made in the etiology of septic shock and organ failure, therapy is still for the most part supportive and largely ineffective. The aim of this review is to summarize the current understanding of the role of lipopolysaccharide in the development of septicemia by examining signal transduction and therapeutic approaches.

Acute-Phase Proteins↗

PubMed1997

Melatonin effects on inhibition of thirst and fever induced by lipopolysaccharide in rat.

In 24 h water deprived rats we have evaluated the effects of melatonin on the inhibition of thirst and on fever induced by Escherichia coli lipopolysaccharide. Intraperitoneal (i.p) injection of lipopolysaccharide (0.32, 0.64 and 0.96 mg/kg) alone induced, a dose-dependent and significant inhibition of water intake as well as fever. In addition, lipopolysaccharide at the same concentrations increased urinary prostaglandins and serum cytokines levels. On the contrary, lipopolysaccharide treatment had no effects on cerebral brain nitric oxide synthase activity. All lipopolysaccharide effects were reverted by a prior, concomitant and subsequent i.p. treatment with melatonin (2, 4 and 6 mg/kg), whereas they were still present when melatonin was injected in combination with the melatonin receptor antagonist luzindole (15, 30 and 60 mg/kg, i.p.). We suggest that melatonin could exert its dipsogenic effects through a reduction of the free radical nitric oxide (NO.) whereas it may reduce body temperature by preventing an excessive formation of prostaglandins and cytokines.

Animals↗

PubMed1997

Induction of nitric oxide synthase by lipopolysaccharide and its inhibition by auranofin in RAW 264.7 cells.

In RAW 264.7 cells, a murine macrophage cell line, treatment with lipopolysaccharide (1 to 10 ng/ml) stimulated production of nitric oxide (NO), which was inhibited by L-N(G)-monomethyl-L-arginine acetate, an inhibitor of NO synthase. Auranofin, an orally active chrysotherapeutic agent, also inhibited the lipopolysaccharide-induced NO production in a concentration-dependent manner (0.3 to 3 microM). Other gold salts such as aurothioglucose and aurothiomalate had no effect. Western blot analysis demonstrated that the lipopolysaccharide (10 ng/ml)-induced expression of inducible NO synthase protein was inhibited by auranofin as well as by the protein synthesis inhibitor cycloheximide. In addition, the lipopolysaccharide-induced increase in the level of mRNA for inducible NO synthase was also lowered by auranofin. Furthermore, auranofin showed no direct effect on the conversion of [3H]arginine to [3H]citrulline by the cell lysate. These findings indicate that auranofin inhibits lipopolysaccharide-induced NO production by suppressing the expression of inducible NO synthase.

Animals↗

PubMed1996

Lipopolysaccharide of the Helicobacter pylori type strain NCTC 11637 (ATCC 43504): structure of the O antigen chain and core oligosaccharide regions.

Smooth- and rough-form lipopolysaccharides from phenol-water extraction of cells from Helicobacter pylori type strain NCTC 11637 were isolated as the water-soluble component of high-M(r) and water-insoluble low-M(r) gel. Structural investigations were performed on the intact water-soluble smooth-form lipopolysaccharide, various oligosaccharides formed as chemical and enzymic degradation products, and three oligosaccharide fractions liberated by acetic acid hydrolysis from the water-insoluble rough-form lipopolysaccharide. A structure is proposed for the complete polysaccharide component of the smooth-form lipopolysaccharide comprising the O antigen chain, an intervening region, and the inner core oligosaccharide on the basis of 1H and 13C NMR experiments, fast atom bombardment/mass spectrometry, and methylation linkage analysis of permethylated oligo- and polysaccharide derivatives. The most striking feature of the O antigen region in the lipopolysaccharide is the presence of extended chains with fucosylated and nonfucosylated N-acetyllactosamine (LacNAc) units that mimic human cell surface glycoconjugates in normal human granulocytes. The chains are terminated by di- or trimeric Lewis(x) (Le(x)) determinants, which are also found in tumor-associated carbohydrate antigens in many adenocarcinomas.

Carbohydrate Conformation↗

PubMed1973

The mitogenic effect of lipopolysaccharide on bone marrow-derived mouse lymphocytes. Lipid A as the mitogenic part of the molecule.

Lipopolysaccharides with different structure, isolated from different mutant strains of Escherichia coli and Salmonella bacteria, and chemical degradation products of these lipopolysaccharides have been employed to investigate which part of the lipopolysaccharide molecule exerts mitogenic effects on bone marrow-derived mouse lymphocytes. Within the structure of lipopolysaccharide consisting of lipid A, a core polysaccharide, and the O-polysaccharide antigen, lipid A was found to be the mitogenic part. The mitogenic effect of lipid A, consisting of phosphorylated glucosamine disaccharide units with ester- and amide-linked fatty acids, was lost after alkali treatment, which removes ester-linked fatty acids. Insertion of the lipid A portion of lipopolysaccharides into the lipid bilayer of the plasma membranes of bone marrow-derived lymphocytes is discussed as the initial mitogenic action.

Antibody Formation↗

PubMed2007

MnTBAP, a synthetic metalloporphyrin, inhibits production of tumor necrosis factor-alpha in lipopolysaccharide-stimulated RAW 264.7 macrophages cells via inhibiting oxidative stress-mediating p38 and SAPK/JNK signaling.

Antioxidants are able to inhibit inflammatory gene expression in response to lipopolysaccharide via down-regulating generation of intracellular reactive oxygen species (ROS) as second messengers. The effect of manganese (III) tetrakis (4-benzoic acid) porphyrin (MnTBAP), a synthetic metalloporphyrin with antioxidant activity, on tumor necrosis factor (TNF)-alpha production in lipopolysaccharide-stimulated RAW 264.7 macrophage cells was examined. MnTBAP prevented the generation of intracellular ROS in lipopolysaccharide-stimulated RAW 264.7 cells and further inhibited lipopolysaccharide-induced TNF-alpha production. MnTBAP exclusively prevented the phosphorylation of p38 mitogen-activated protein kinase (MAPK) and stress-activated protein kinase (SAPK/JNK) whereas it did not affect the phosphorylation and activation of nuclear factor-kappaB and extracellular signal regulated kinase 1/2. MnTBAP was suggested to inhibit lipopolysaccharide-induced TNF-alpha production by the prevention of intracellular ROS generation and subsequent inactivation of p38 MAPK and SAPK/JNK.

Animals↗