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PubMed1991

Endotoxin shedding by enterobacteria: free and cell-bound endotoxin differ in Limulus activity.

The endotoxin activities of gram-negative bacteria and their lipopolysaccharides (LPS) have been quantitated by a chromogenic Limulus amocbocyte lysate (CLAL) assay. When bacterial cell exposing various cell surface structures were compared, the highest Limulus activities were found in R strains of Escherichia coli and Salmonella typhimurium mutants. E. coli with K antigens did not differ from K-negative strains. By measuring beta-hydroxymyristic acid (3-OH tetradecanoic acid, beta-OHC14:0), it was possible to compare the CLAL activities of LPS bound to bacterial cells, LPS shed into the culture medium, and purified LPS. After 16 h of growth, the cell-free culture supernatants of three E. coli O1K1 strains and S. typhimurium showed CLAL activities 14.3 to 20.3 times higher than did the corresponding bacterial cell suspensions in relation to their beta-OHC14:0 contents. Four other E. coli strains (O serotypes O14, O24, and O75) and the S. typhimurium 395 R mutants MR5 and MR6 showed CLAL values 2.8 to 7.9 times higher in their culture supernatants. LPS of E. coli O1K1 and S. typhimurium had lower CLAL activities than the culture supernatants (1/10 and 1/4, respectively). Although the beta-OHC14:0 concentrations of the culture supernatants were approximately half those of the corresponding bacterial cells, all had CLAL values that were 2 to 21 times higher. The bacterial cell suspension, culture supernatant, and purified LPS of S. typhimurium MS were compared by CLAL assay and a quantitative enzyme-linked immunosorbent assay based on monoclonal antibodies to the O5 antigen. Endotoxin shed into the culture medium was the most CLAL-active form of LPS, while purified LPS was the most antigen-active form. The results emphasize the importance of appropriate standards when quantifying endotoxin in various states. In conclusion, E. coli and S. typhimurium bacteria shed significant amounts of endotoxin into the surrounding medium during growth. This form of LPS is more CLAL active than the cell-bound or purified LPS.

Animals↗

PubMed1965

High Susceptibility of Strain A Mice to Endotoxin and Endotoxin-Red Blood Cell Mixtures.

Heppner, Gloria (University of California, Berkeley), and David W. Weiss. High susceptibility of strain A mice to endotoxin and endotoxin-red blood cell mixtures. J. Bacteriol. 90:696-703. 1965.-Strain A mice were shown to be considerably more susceptible to lethal effects of endotoxin lipopolysaccharide (LPS) than mice of several other strains. Complexes of sublethal quantities of LPS and sheep red blood cells were synergistically toxic for strain A mice. Separate administration of sheep red blood cells and heat-killed salmonellae, in either order and as long as 24 hr apart, also proved to be synergistically lethal for strain A mice, but not for R(III) animals studied comparatively. Sheep red blood cell lysates possessed the ability of the intact cells in forming lethal combinations for strain A mice with killed salmonellae. Strain A red blood cell-killed salmonellae complexes were also lethal for strain A mice, but less so then complexes made with sheep red blood cells. A x R(III) F(1) hybrid animals showed the same resistance characteristics as the resistant R(III) parental strain. Possible explanations for these findings are suggested, and their relevance to an immunological mode of action of endotoxin lethality is discussed.

Journal Article↗

PubMed2000

Interaction of bacterial endotoxins with chitosan. Effect of endotoxin structure, chitosan molecular mass, and ionic strength of the solution on the formation of the complex.

The interaction of endotoxins of different structure (lipopolysaccharides (LPS) and lipopolysaccharide-protein complexes (LPPC)) with chitosan has been studied. It was shown that the mechanism of interaction is rather complicated and depends on the macromolecular organization of endotoxin as well as on the degree of polymerization of the chitosan. Chitosan with molecular mass of 20 kD reveals higher affinity to LPS than chitosan with molecular mass of 140 kD. Endotoxins with long O-specific chains can bind completely with chitosan with the formation of LPS-chitosan and LPPC-chitosan complexes with weight ratios between the original components of 1:1 and 1:5. When endotoxins with higher degree of hydrophobicity and short O-specific chains were mixed with chitosan, a part of the LPS remained unbound. The stability of the complexes formed depends on ionic strength. It was shown that, in addition to electrostatic forces, other types of forces take part in the formation of the complexes. A decrease in acute toxicity of various LPSs is observed on their binding with chitosans.

Animals↗

PubMed1998

[Induction of early endotoxin tolerance with atoxic endotoxin--a new method for preventing sepsis syndrome].

The induction of early-phase endotoxin tolerance in a procine endotoxin shock model by atoxic LPS from Rhodobacter sphaeroides led to a significant extension of the survival time (p < 0.0179). The protective effect of the non-specific tolerant state also led to an enhancement of cardiorespiratory parameters during the continuous endotoxin challenge. Non-specific stimulation of host defense mechanisms with atoxic endotoxin as prophylactic agent in surgical patients at risk may prove to be beneficial in the future.

Animals↗

PubMed1991

Time course of IL-6 and TNF alpha release during endotoxin-induced endotoxin tolerance in rats.

Development of endotoxin tolerance in rats induced by repeated application of low dosages of endotoxin is associated with repeatable IL-6 formation, reversible drop in white blood cells, pronounced consumption of platelets, gradual formation of alpha 2M as an example of acute phase proteins, and flattening TNF alpha formation. In the status of full tolerance the TNF alpha release is completely eliminated. Inhibition of TNF alpha biosynthesis and induction of acute phase protein formation by IL-6 are discussed as possible factors in the development of endotoxin tolerance.

Acute-Phase Proteins↗

PubMed1988

Detergent-accelerated hydrolysis of bacterial endotoxins and determination of the anomeric configuration of the glycosyl phosphate present in the "isolated lipid A" fragment of the Bordetella pertussis endotoxin.

Due to the formation of micelles, severance of the hydrophilic (poly- or oligosaccharide) and hydrophobic ("Lipid A") domains of bacterial lipopolysaccharides at pH 3.4 or 4.5 and 100 degrees is slow and sometimes does not proceed at all; partially degraded fragments are usually formed. At pH 3.4 (100 degrees) in aqueous 1% sodium dodecylsulphate (SDS), both lipopolysaccharides of the Bordetella pertussis endotoxin are cleaved within 20-30 min, but 80% of the glycosidically bound phosphate present in the hydrophobic domain is lost. Other endotoxins behave similarly. At pH 4.5 (100 degrees) and in the absence of detergent, hydrolysis of the glycosidic bonds of 3-deoxy-D-manno-2-octulosonic acid residues of the B. pertussis endotoxin is negligible but, in aqueous 1% SDS, severance of the two regions of LPS 1 is complete within 1 h (that of LPS-2 requires 3-4 h), and the glycosidically bound phosphate of the isolated hydrophobic region is preserved. Comparison of the rate of acid-catalysed hydrolysis of the glycosidically bound phosphate present in this "isolated Lipid A" preparation with that of 2-deoxy-2-[(3R)-3-hydroxytetradecanamido]-alpha- and -beta-D-glucopyranose 1-phosphates established that the former 1-phosphate was the alpha anomer.

Bordetella pertussis↗

PubMed1989

The effects of endotoxin pretreatment on subsequent challenge of mice with cycloheximide and a small dose of endotoxin.

Mice treated with 15.0 micrograms of S. enteritidis endotoxin are completely protected against the coagulopathic effects, but only partially protected against the fatal glucocorticoid deficiency which follow an otherwise lethal challenge with cycloheximide and 5.0 micrograms of the same endotoxin given 3 days later. Hydrocortisone treatment results in survival of all such tolerant, challenged animals. The protection conferred against occlusion of glomerular capillaries by fibrin coagula is abolished by EACA, suggesting that tolerance has induced high levels of fibrinolytic activity by the time of challenge, and evidence indicates that this protective degree of fibrinolytic activity persists for more than 24 h after cycloheximide and endotoxin challenge.

Aminocaproic Acid↗

PubMed1994

Endotoxin elicits normal tryptophan and indolamine responses but impaired catecholamine and pituitary-adrenal responses in endotoxin-resistant mice.

The neurochemical and endocrine responses to endotoxin (LPS), Newcastle disease virus (NDV) and interleukin-1 (IL-1) administration were studied in endotoxin-resistant mice. LPS has long been known to be a potent stimulator of the hypothalamo-pituitary-adrenocortical axis, but it also increases brain concentrations of the catabolites of norepinephrine (NE) and serotonin (5-HT), as well as free tryptophan. Mice of the endotoxin-resistant C3H/HeJ strain showed markedly reduced responses in plasma ACTH and corticosterone (CS) to intraperitoneal LPS compared to the control C3H/HeN strain. C3H/HeN mice displayed increases in the cerebral NE catabolite, MHPG, and the dopamine catabolite, DOPAC, but no such increases occurred in C3H/HeJ mice. However, the indolaminergic responses, increases of tryptophan and the serotonin catabolite, 5-HIAA, were similar in the two strains. NDV administration induced responses very similar to those of LPS; increases in tryptophan and 5-HIAA, but impaired responses in catecholamines, ACTH and CS. IL-1 is known to be synthesized and secreted following LPS (and probably NDV) administration, and produces similar endocrine and neurochemical effects. In C3H/HeJ mice, IL-1 elicited normal increases in plasma ACTH and CS, as well as cerebral MHPG, 5-HIAA and tryptophan. Thus the deficits in C3H/HeJ mice do not reflect alterations in the ability of catecholamines and the HPA axis to respond to the immune system, but probably occur early in the sequence of reactions initiated by LPS and NDV. These results also suggest that LPS activates cerebral catecholamines and the HPA axis by similar or related mechanisms, whereas the indolaminergic responses apparently occur via a different mechanism.

Animals↗

PubMed1994

Octreotide does not alter endotoxin lethality in mice or endotoxin-induced suppression of human leukocyte migration.

Octreotide, a somatostatin analog, was evaluated for its effects on long-term survival in a mouse model of endotoxemia and for its effects on endotoxin-induced suppression of human leukocyte migration. Swiss Webster mice were simultaneously rendered endotoxemic with a single intraperitoneal injection of 800 micrograms E. coli Lipopolysaccharide (LPS) and treated with one of four doses of subcutaneous (s.c.) octreotide (1.0 mg/kg in 0.4 ml saline, 0.1 mg/kg in 0.4 ml saline, 0.1 mg/kg in 0.04 ml saline, or 0.001 mg/kg in 0.04 ml saline) or saline alone (fluid-resuscitated control group: 0.4 ml saline s.c.; or non-fluid-resuscitated control group: 0.04 ml saline s.c.). Octreotide was continued with or without supplemental s.c. fluid resuscitation (0.4 ml saline) at eight hour intervals for either twenty-four or forty hours. There was no statistical significance to differences in long-term survival between comparable groups of octreotide treated vs saline treated animals during the entire fourteen day period of observation. Fluid resuscitation during the first forty hours following endotoxemia induction delayed death, but did not significantly improve long-term survival. In vitro work was conducted to determine the effect of octreotide on endotoxin-induced suppression of human leukocyte migration. Octreotide at concentrations ranging from 3.05 x 10(-5) Molar to 3.05 x 10(-11) Molar had no significant effect on leukocyte migration. In this study octreotide treatment failed to improve long-term survival in mice with endotoxemia and did not alter endotoxin-induced suppression of leukocyte migration.

Animals↗

PubMed1984

The effect of endotoxin and radio-detoxified endotoxin on the serum T4 level of rats and response of their thyroid gland to exogenous TSH.

We have demonstrated that, while the shock-inducing dose of parent (toxic) endotoxin significantly decreases the serum T4 level of rats and inhibits the T4 response given to exogenous thyroid stimulating hormone (TSH), the radio-detoxified (60Co-gamma, 150 kGy) endotoxin preparation does not inhibit the response to exogenous TSH and decreases serum T4 level to a lesser extent than untreated endotoxin.

Animals↗

PubMed1985

Cellular effects of endotoxin in vitro: mobility of endotoxin in the plasma membrane of hepatocytes and neuroblastoma cells.

Lipopolysaccharide labeled with fluorescein isothiocyanate (FITC-LPS) was used to examine interactions between endotoxin and plasma membrane in isolated rat hepatocytes and mouse neuroblastoma NB41A3 cells. At the same endotoxin to cell ratio, hepatocytes bound more toxin than did neuroblastoma cells. At a dose of 12 micrograms/mg dry wt, a bound mobile fraction of between 60 and 75% of FITC-LPS was found on hepatocytes at 25 degrees C with a lateral diffusion coefficient (D) of 4.0 X 10(-9) cm2/s. In neuroblastoma cells, the mobile fraction was larger (85-90%), with D 1.0 X 10(-8) cm2/s. D was temperature-dependent between 10 and 37 degrees C and increased from 1.8 X 10(-9) to 1.0 X 10(-8) cm2/s in hepatocytes and from 9.4 X 10(-9) to 1.9 X 10(-8) cm2/s in neuroblastoma cells. In both types of cell, nonviable (cells which did not exclude Trypan blue) as compared to viable cells showed different recovery patterns and 100% of the probe molecules were mobile. These results suggest that: (1) endotoxin binding to mammalian cells consists of two subpopulations with different mobilities; (2) binding of the immobile fraction is dependent on cellular integrity; and (3) the differences in binding, lateral mobility, and size of the immobile fraction in hepatocytes and neuroblastoma cells may be due to variations in membrane composition and/or number of binding sites.

Animals↗

PubMed1962

Studies on the biologic relationship of endotoxin and other toxic proteins. I. Comparison of the properties of snake venom and endotoxin.

1. Agkistrodon piscivorus venom and E. coli endotoxin were shown to be immunologically distinct, and to differ in certain biologic properties: effects on immune response, body temperature, and circulating leukocyte count, and capacity to prepare for and provoke the local and generalized Shwartzman reaction. 2. Neither a single prior injection of venom nor the existence of hyperimmunity to lethal doses of venom protected rabbits against the local and generalized Shwartzman reaction. 3. Serial intravenous injections of sublethal doses of venom produced enhanced susceptibility to venom rather than refractoriness. 4. Preparation for both the local and generalized Shwartzman reaction with endotoxin appeared to enhance susceptibility of rabbits to challenge with venom. 5. Tolerance to bacterial pyrogens established by repeated injections of endotoxin is paralleled by increased resistance to snake venom given at least 1 week later, in mice and rabbits. 6. Zymosan failed to enhance susceptibility of rabbits to venom, but thorotrast increased the number of late deaths from venom. 7. Exposure of venom to ferrous sulfate interferes with its toxicity.

Animals↗

PubMed1999

Dose-related inflammatory effects of intravenous endotoxin in humans: evaluation of a new clinical lot of Escherichia coli O:113 endotoxin.

The administration of reference endotoxin (Escherichia coli O:113, Lot EC-5) to humans has been an important means to study inflammation in vivo; however, the supply of Lot EC-5 is depleted. A new lot of reference endotoxin (Clinical Center reference endotoxin [CCRE]), derived from the original bulk material extracted from E. coli O:113, was processed. The effects of 0-, 1-, 2-, and 4-ng/kg doses of intravenous CCRE and EC-5 were studied in 20 male subjects. CCRE resulted in dose-related increases in symptoms, temperature (P=. 016), total leukocyte count (P=.014), tumor necrosis factor-alpha (P=.004), interleukin (IL)-1 receptor antagonist (P=.004), IL-6 (P=. 005), IL-8 (P=.011), cortisol (P<.05), and C-reactive protein (P=. 04). These responses were attenuated (all P<.012) in subjects given Lot EC-5 (4 ng/kg) in comparison with those in subjects given CCRE, showing that, over several years, EC-5 had lost potency. Thus, in healthy subjects, the magnitude of exposure to CCRE results in a graded dose response of major components of innate immunity.

Adult↗

PubMed1977

Inhibition of Na+, K+-adenosinetriphosphatase by endotoxin: a possible mechanism for endotoxin-induced cholestasis.

Cholestatic jaundice is one complication of nonhepatic gram-negative bacterial infection. The endotoxin of Escherichia coli has been reported to cause cholestasis by inhibiting the bile salt-independent fraction (BSIF) of bile in the perfused rat liver. Accordingly, the effects of lipopolysaccharides (LPS) of E. coli and Salmonella enteritidis on the Na+, K+-adenosinetriphosphatase (ATPase) in canalicular-enriched plasma membranes of rate liver were examined. At 20 microgram/ml, both endotoxins inhibited this enzyme by approximately 40%. Maximal inhibition (70%-80%) occurred at concentrations of greater than or equal to 120 microgram/ml. The LPS of neither organism exerted any effect on the activity of Mg++-ATPase or 5'-nucleotidase in the same preparations. Inhibition by the E. coli LPS appeared to be noncompetitive in nature, and the calculated Ki was 45 microgram/ml. Since the Na+, K+-ATPase may be responsible for the elaboration of BSIF, inhibition of this enzyme could be the underlying mechanism for the endotoxin-induced cholestasis.

Adenosine Triphosphatases↗

PubMed1995

Endotoxin pretreatment of human monocytes alters subsequent endotoxin-triggered release of inflammatory mediators.

In trauma or sepsis, monocytes and macrophages release mediators such as tumor necrosis factor (TNF), interleukin-1 (IL-1), interleukin-6 (IL-6), and prostaglandin E2 (PGE2). Although patients may be exposed to more than one stimulus, the effect of repetitive endotoxin (LPS) stimulation on human monocytes is poorly characterized. Human peripheral blood monocytes obtained from healthy volunteers were pretreated with endotoxin (LPS1) for 24 h. Cultures were then restimulated for 24 h with a second, activating LPS stimulus (LPS2) at various concentrations and supernatant mediators (TNF, IL-1, IL-6, and PGE2) measured. Serum cytokine levels of normal monocyte donors were compared to basal and LPS-stimulated cytokine release of their monocytes in vitro. LPS2 increased all mediators in a dose-dependent manner in the absence of LPS1 pretreatment. LPS1 significantly increased LPS2-triggered monocyte secretion of IL-1, IL-6, and PGE2, but inhibited TNF release. Cell-associated TNF and IL-1 were also inhibited and enhanced in parallel with supernatant levels of the respective cytokines. Serum cytokine levels were low, showed wide variation, and correlated poorly with in vitro LPS-triggered cytokine production. Human monocyte mediator production is differentially regulated by endotoxin pretreatment. Provocative in vitro testing of monocytes could identify prior LPS exposure and may be more useful than serum cytokine measurements.

Adult↗

PubMed1987

Endotoxin-polymyxin complexes in an improved enzyme-linked immunosorbent assay for IgG antibodies in blood donor sera to gram-negative endotoxin core glycolipids.

Common or cross-reactive epitopes of Gram-negative endotoxins are found in the inner-core glycolipid region of the outer membrane lipopolysaccharides (LPS). Hydrophobic LPS from rough mutants of Gram-negative bacteria, lacking serotype polysaccharide O-antigen chains, did not bind satisfactorily to polystyrene microplates for ELISA detection of cross-reactive IgG anti-endotoxin antibodies. When these LPS molecules were reacted with the cationic polypeptide polymyxin B, complexes were formed which were stable when coated on microplates. LPS-polymyxin complexes allowed optimisation of conditions for an ELISA for IgG antibodies to the core glycolipid region of endotoxins which could be used for screening large numbers of blood donor sera.

Antibodies, Anti-Idiotypic↗

PubMed1977

Some effects of prostaglandins E1 and E2 and of endotoxin injected into the hypothalamus of young chicks: dissociation between endotoxin fever and the effects of prostaglandins.

Prostaglandins E1 and E2 elevated body temperature of young chicks when injected into the hypothalamus at thermoneutrality (31 degrees C). In contrast, they lowered body temperature when so injected below thermoneutrality (16degreesC): the relation of the fall in body temperature to increased heat loss and decreased heat production was examined. 2 The above effects below thermoneutrality were potentiated by pretreatment with inhibitors of prostaglandin synthetase and possible reasons for this potentation are given. 3 The O-somatic antigen of Shigella dysenteriae consistently evoked hyperthermia when injected into the hypothalamus, irrespective of whether the chicks were within or below thermoneutrality. 4 Pretreatment with prostaglandin synthetase inhibitors failed to prevent the onset of endotoxin fever; however, duration of the fever, induced by intrahypothalamic injection of the O-somatic antigen of Shigella dysenteriae was reduced. 5 The intrahypothalamic injection, belwo thermoneutrality of prostaglandins E1, E2, noradrenaline, 5-hydroxytryptamine or carbachol reversed endotoxin fever, inducing even substantial falls in body temperature. 6 While the results cast some doubts on the role of prostaglandins of the E series as mediators of endotoxin fever in chicks, they cannot be eliminated as mediators until the significance of the reduction in duration of the pyrexic response by indomethacin and 5,8,11,14-eicosatetraynoic acid, and the degree of synthesis inhibition attained, are known.

5,8,11,14-Eicosatetraynoic Acid↗

PubMed1979

Polymyxin B sulfate modification of bacterial endotoxin: effects on the development of endotoxin shock in dogs.

The effects of endotoxin (lipopolysaccharide [LPS]) on the pathogenesis of canine endotoxin shock were compared with those of LPS which had interacted with polymyxin B sulfate prior to administration. Both LPS and polymyxin B-modified LPS caused comparable early decreases in aortic blood pressure, leukocyte and platelet numbers, and serum complement levels. However, in dogs receiving polymyxin B-modified LPS the late hypotensive phase was significantly ameliorated and lethality was significantly decreased. These data indicate that polymyxin B-modified LPS, though significantly less lethal than unmodified LPS, was capable of major interactions with several components of the humoral defense system, and support the concept that such interactions are not determinative in the pathogenesis of canine endotoxin shock.

Animals↗