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PubMed2005

Thermoregulatory responses of rats to conventional preparations of lipopolysaccharide are caused by lipopolysaccharide per se-- not by lipoprotein contaminants.

LPS preparations cause a variety of body temperature (T(b)) responses: monophasic fever, different phases of polyphasic fever, and hypothermia. Conventional (c) LPS preparations contain highly active lipoprotein contaminants (endotoxin proteins). Whereas LPS signals predominantly via the Toll-like receptor (TLR) 4, endotoxin proteins signal via TLR2. Several TLR2-dependent responses of immunocytes to cLPS in vitro are triggered by endotoxin proteins and not by LPS itself. We tested whether any T(b) response to cLPS from Escherichia coli 055:B5 is triggered by non-TLR4-signaling contaminants. A decontaminated (d) LPS preparation (free of endotoxin proteins) was produced by subjecting cLPS to phenol-water reextraction. The presence of non-TLR4-signaling contaminants in cLPS (and their absence in dLPS) was confirmed by showing that cLPS (but not dLPS) induced IL-1beta expression in the spleen and increased serum levels of TNF-alpha and IL-1beta of C3H/HeJ mice; these mice bear a nonfunctional TLR4. Yet, both cLPS and dLPS caused cytokine responses in C3H/HeOuJ mice; these mice bear a fully functional TLR4. We then studied the T(b) responses to cLPS and dLPS in Wistar rats preimplanted with jugular catheters. At a neutral ambient temperature (30 degrees C), a low (0.1 microg/kg iv) dose of cLPS caused a monophasic fever, whereas a moderate (10 microg/kg iv) dose produced a polyphasic fever. In the cold (20 degrees C), a high (500 microg/kg iv) dose of cLPS caused hypothermia. All T(b) responses to dLPS were identical to those of cLPS. We conclude that all known T(b) responses to LPS preparations are triggered by LPS per se and not by non-TLR4-signaling contaminants of such preparations.

Animals↗
PubMed1990

Deacylated lipopolysaccharide inhibits plasminogen activator inhibitor-1, prostacyclin, and prostaglandin E2 induction by lipopolysaccharide but not by tumor necrosis factor-alpha.

Bacterial LPS and TNF induce vascular endothelial cells to express a variety of response molecules. LPS that is partially deacylated (dLPS) by a human neutrophil enzyme blocks the ability of LPS, but not TNF, to augment one of these responses, the expression of endothelial cell surface molecules that promote neutrophil adherence (J. Exp. Med. 1987; 165:1393-1402). We show that dLPS can inhibit the ability of LPS, but not TNF, to elicit the expression of plasminogen activator inhibitor-1 (PAI-1), prostacyclin, and PGE2 by human umbilical vein endothelial cells. dLPS also prevented the accumulation of specific PAI-1 mRNA in response to LPS, but not to TNF. Neither the LPS- or TNF-induced expression of PAI-1 nor the dLPS inhibition of the LPS response was mediated by prostanoids. These results indicate that dLPS can specifically block a variety of endothelial cell responses to LPS and provide support for the hypotheses 1) that dLPS and LPS may interact with a common target molecule on or in endothelial cells, and 2) that dLPS, produced by enzymatic deacylation of LPS in vivo, could inhibit endothelial cell stimulation by LPS and thereby limit the host inflammatory response to invasive gram-negative bacteria.

Acylation↗
PubMed1986

[Effect of the cultivation temperature on the production of biomass and lipopolysaccharide as well as the chemical composition and antigenicity of the lipopolysaccharide of S-forms and R-mutants of the genus Salmonella].

The effect of different temperatures (30 to 43 degrees C) on Salmonella S forms and R mutants in fermentor mass cultures was studied. It was found that for the velocity of substrate utilization, for maximum LPS biosynthesis as well as for maximum biosynthesis of bacterial cell-mass the respective optimum temperature was different. In the case of S-form strains and of one SR mutant a cultivation temperature of 34 degrees C proved optimum for maximum yield of LPS. At this temperature the yield of bacterial cell-mass was only somewhat lower than that obtained at 37 degrees C. Also the cultivation time necessary although longer, remained within tolerable limits. In the case of R mutants maximum yields of bacterial cell-mass were obtained at 30-34 degrees C, however, a common optimum temperature for LPS biosynthesis did not become evident. Chemical and serological analysis of the LPS revealed that neither the pattern of fatty acids in lipid A nor O-antigen factors, 1, 5 and 12(2) were influenced in any way by the cultivation temperature in the range of 30-34 degrees C. Similarly no temperature-dependent changes in the antigenic specificity of monospecific R mutants were seen. In contrast the growth temperature had a marked influence on the number of repeating units in the O-polysaccharide and also on the number of LPS molecules with free core stubs (R form LPS) occurring in isolated S form LPS. Further in the case of a double mutant, the growth temperature had some influence on the expression of one of the R specificities.

Antigens, Bacterial↗
PubMed1989

Human endothelial cell adhesiveness for neutrophils, induced by Escherichia coli lipopolysaccharide in vitro, is inhibited by Bacteroides fragilis lipopolysaccharide.

Recent studies in vitro have demonstrated that LPS from Gram-negative bacteria are capable of inducing endothelial cells to express a cell surface property that promotes the adherence of neutrophils (polymorphonuclear cells, PMN). We have investigated the effects of LPS from Bacteroides fragilis, an organism documented to have little toxicity in vivo, on the induction of this property in human endothelial cells. Monolayers of cultured human umbilical vein endothelial cells (HUVE) exhibited no increase in adhesiveness for 51Cr-radiolabeled PMN after 4 h of exposure to B. fragilis LPS from 1 ng to 10 micrograms/ml. Escherichia coli LPS elicited a dose-dependent enhancement of HUVE adhesiveness for PMN over the same concentration range, reaching a maximum of 49.4 +/- 6.6% at 10 micrograms/ml. Like E. coli LPS, B. fragilis LPS converted chromogenic substrate in the Limulus amebocyte lysate assay, and was directly cytotoxic to bovine aortic endothelial cells. Both B. fragilis LPS activities required doses two-to-three log-fold higher than for E. coli LPS. In addition, we found that B. fragilis LPS inhibited the induction of HUVE adhesiveness for PMN by E. coli LPS. This inhibition was also dose-dependent, becoming maximal (greater than 80%) when B. fragilis LPS was in 10- to 20-fold excess. Tumor necrosis factor and IL-1, two monokines which also elicit HUVE adhesiveness for PMN, were not inhibited by B. fragilis LPS, suggesting a mechanism of HUVE activation by LPS which is signal-specific, and which recognizes specificities of LPS structure.

Bacteroides fragilis↗
PubMed1988

Inhibition of lipopolysaccharide activation of 7OZ/3 cells by anti-lipopolysaccharide antibodies.

We have investigated the ability of mAb against LPS to inhibit LPS-induced activation of 7OZ/3 pre-B cells. The fine specificity and relative affinity of these mAb for lipid A and LPS were also determined. We found that antibodies inhibited only the activity of glycolipids which they bound with relatively high affinity. However, two high affinity antibodies binding to non-lipid A epitopes did not block cellular activation. Some, but not all, relatively high affinity antibodies binding to the lipid A region of the LPS molecule inhibited biologic activity. The inhibitory antibodies bound to at least two distinct epitopes within the lipid A region. These data suggest that LPS interacts with 7OZ/3 cells in a highly specific fashion.

Animals↗
PubMed1993

Protein tyrosine kinase inhibitors decrease induction of nitric oxide synthase activity in lipopolysaccharide-responsive and lipopolysaccharide-nonresponsive murine macrophages.

We investigated tumoricidal activation and induction of nitric oxide synthase (NOS) activity in macrophages from LPS-responsive (C3H/HeN) and -unresponsive mice (C3H/HeJ). Macrophages were incubated in vitro with a synthetic lipopeptide or with LPS and IFN-gamma. LPS and IFN-gamma activated C3H/HeN but not C3H/HeJ macrophages to lyse B16 melanoma cells. In contrast, lipopeptide and IFN-gamma activated macrophages from both strains of mice. Genistein, a specific inhibitor of protein tyrosine kinase, significantly blocked tumoricidal activation of macrophages from both strains of mice. Genistein did not affect tumor cell binding but significantly inhibited the production of nitric oxide. Genistein, herbimycin A, and tyrphostin inhibited the induction of NOS activity in macrophages from both strains of mice. These data suggest that protein tyrosine kinase activity is involved in the signal transduction pathway of LPS and other synthetic bacterial-related immunomodulators at a point preceding triggering of macrophage tumoricidal activation and expression of inducible NOS activity.

Amino Acid Oxidoreductases↗
PubMed1996

Zinc enhances lipopolysaccharide-induced monokine secretion by alteration of fluidity state of lipopolysaccharide.

Elevated zinc serum concentrations have been shown to restore impaired immune response. Therefore, pharmacologic zinc supplementation has been used to improve immune function, particularly in intensive care patients. In these patients, Gramnegative sepsis, the symptoms of which are predominantly caused by LPS-induced release of monokines, represents a serious problem. We have recently shown that zinc enhances induction of TNF-alpha and IL-1 beta in cultures of PBMC by LPS. By fluorescence polarization and infrared spectroscopic measurements we found that zinc addition leads to decreased fluidity of the hydrocarbon chains of LPS. Experiments at different temperatures showed that the less fluid gel (beta) phase of LPS is more effective in cytokine induction than the more fluid liquid-crystalline (alpha) phase. Our studies suggest that the synergistic effect of zinc on monokine induction by LPS is caused by direct interaction of zinc with LPS altering the fluidity of the hydrocarbon chains. Although this effect is zinc specific, other divalent ions, like cobalt and nickel, with a complex structure and size comparable to those of zinc also enhance LPS-induced monokine secretion but to a much lesser extent. Our data indicate that the zinc level represents a relevant clinical parameter in the treatment of Gram-negative infection. This reveals potential risks in the therapeutic application of zinc.

Adjuvants, Immunologic↗
PubMed1996

Tolerance to lipopolysaccharide-induced increase in vascular permeability in mouse skin.

We investigated whether tolerance develops to the lipopolysaccharide-induced increase in vascular permeability of mouse skin on pretreatment with Salmonella typhimurium lipopolysaccharide. Lipopolysaccharide-induced plasma extravasation was assessed by determining Pontamine sky blue dye accumulation in the skin where lipopolysaccharide was injected s.c. 2 h previously. When mice were pretreated with lipopolysaccharide (0.15 mg/kg i.p.), the dye leakage induced by s.c. challenge with lipopolysaccharide (400 micrograms/site) was significantly, inhibited for 2-24 h after pretreatment, indicating the development of lipopolysaccharide tolerance. At 4 h after lipopolysaccharide (0.15 mg/kg i.p.), the dose-response curve of dye leakage against the challenge dose of lipopolysaccharide shifted about 2-fold to the higher dose. The dye leakage induced by lipopolysaccharide was inhibited by pretreatment with lipopolysaccharide in a dose-dependent manner (0.05-0.15 mg/kg i.p.). Lipopolysaccharide tolerance was not seen in adrenalectomized mice. When mice were pretreated with lipopolysaccharide and NG-nitro-L-arginine methyl ester (L-NAME), a nitric oxide (NO) synthase inhibitor, at the same time, the hyporesponsiveness to lipopolysaccharide challenge disappeared. However, L-NAME was ineffective to inhibit the development of lipopolysaccharide tolerance when administered 24 h after lipopolysaccharide pretreatment or just before the lipopolysaccharide challenge. Tumor necrosis factor-alpha and interleukin-1 alpha but not interleukin-6 induced a similar hyporesponsiveness to lipopolysaccharide. These results suggest that tolerance develops to the lipopolysaccharide-induced increase in vascular permeability in mouse skin after a single lipopolysaccharide administration and that endogenous glucocorticoids and NO are necessary for induction of lipopolysaccharide tolerance. Hyporesponsiveness induced by lipopolysaccharide pretreatment may be mediated by production of some cytokines such as tumor necrosis factor-alpha or interleukin-1 alpha.

Animals↗