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Endotoxins (LPS) are highly potent immune stimulatory molecules and are mainly known for triggering Gram-negative sepsis. However, besides their toxic effects, this stimulatory function may be advantageous, for example when used as an adjuvant during vaccination. Thus, there is always a narrow range between the useful wake-up of the immune system and its overwhelming reaction, which can lead to diseases like sepsis. This raises the question of which conformational properties are responsible for making the LPS aggregates more or less potent. As described previously, the size, type and form of LPS aggregates play a major role in their immune stimulatory activity. In this study we investigate the role of these parameters. On the one hand, we use a peptide (Pep19-2.5; Aspidasept) that causes a change of the LPS aggregate structure into a less toxic state; on the other hand, we use a potent immune stimulating peptide (Hbγ-35), leading to higher toxicity. We have found opposing effects on LPS aggregate conformations allowing a better understanding of the processes of immune stimulation., (© The Author(s) 2014 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav.)

Bacterial endotoxin (lipopolysaccharide, LPS) is the major component of the outer leaflet of the outer membrane in gram-negative bacteria. During severe infections, bacteria may reach the blood circuit of humans, and endotoxins may be released from the bacteria due to cell division or cell death. In particular enterobacterial forms of LPS represent extremely strong activator molecules of the human immune system causing a rapid induction of cytokine production in monocytes and macrophages. Various mammalian blood proteins have been documented to display LPS binding activities mediating normally decreasing effects in the biological activity of LPS. In more recent studies, the essential systemic oxygen transportation protein hemoglobin (Hb) has been shown to amplify LPS-induced cytokine production on immune cells. The mechanism responsible for this effect is poorly understood. Here, we characterize the interaction of hemoglobin with LPS by using biophysical methods. The data presented, revealing the changes of the type and size of supramolecular aggregates of LPS in the presence of Hb, allow a better understanding of the hemoglobin-induced increase in bioactivity of LPS.

Richard Pfeiffer, working with Robert Koch in Berlin, intellectually and experimentally conceived the concept of endotoxin as a heat-stable bacterial poison responsible for the pathophysiological consequences of certain infectious diseases. Pfeiffer's definition of endotoxin included the inability to evoke neutralizing antibodies against this bacterial toxin. Alexandre Besredka, Ilya (Elie) Metchnikoff's successor at the Institut Pasteur in Paris, was the first to demonstrate that, in fact, antibodies could be engendered which were capable of suppressing the poisonous effects of endotoxin. Endotoxin and anti-endotoxin antibodies have since then fascinated researchers of many disciplines and continue to do so, particularly in the fields of diagnosis, prevention, and therapy of severe Gram-negative infections.

How does the host sense pathogens? Our present concepts grew directly from longstanding efforts to understand infectious disease: how microbes harm the host, what molecules are sensed and, ultimately, the nature of the receptors that the host uses. The discovery of the host sensors--the Toll-like receptors--was rooted in chemical, biological and genetic analyses that centred on a bacterial poison, termed endotoxin.

Hemoglobin and its structures have been described since the 1990s to enhance a variety of biological activities of endotoxins (LPS) in a dose-dependent manner. To investigate the interaction processes in more detail, the system was extended by studying the interactions of newly designed peptides from the γ-chain of human hemoglobin with the adjuvant monophosphoryl lipid A (MPLA), a partial structure of lipid A lacking its 1-phosphate. It was found that some selected Hbg peptides, in particular two synthetic substructures designated Hbg32 and Hbg35, considerably increased the bioactivity of MPLA, which alone was only a weak activator of immune cells. These findings hold true for human mononuclar cells, monocytes and T lymphocytes. To understand the mechanisms of action in more detail, biophysical techniques were applied. These showed a peptide-induced change of the MPLA aggregate structure from multilamellar into a non-lamellar, probably inverted, cubic structure. Concomitantly, the peptides incorporated into the tightly packed MPLA aggregates into smaller units down to monomers. The fragmentation of the aggregates was an endothermic process, differing from a complex formation but rather typical for a catalytic reaction. [ABSTRACT FROM AUTHOR]

How does the host sense pathogens? Our present concepts grew directly from longstanding efforts to understand infectious disease: how microbes harm the host, what molecules are sensed and, ultimately, the nature of the receptors that the host uses. The discovery of the host sensors — the Toll-like receptors — was rooted in chemical, biological and genetic analyses that centred on a bacterial poison, termed endotoxin. [ABSTRACT FROM AUTHOR]

Examines the structure of an alanine-lacking core tetrasaccharide triphosphate from the lipopolysaccharide (LPS) of Pseudomonas aeruginosa mutant H4. Isolation and characterization of LPS; Analysis of core tetrasaccharide triphosphate; Use of nuclear magnetic resonance spectroscopy.

The O-polysaccharide chain of Legionella pneumophila Philadelphia strain 1 (serogroup 1) lipopolysaccharide was investigated by means of ¹H- and 13C-NMR spectroscopy, and chemical analysis. It was found to consist of an α-(2→4) interlinked homopolymer of a 5-acetamidino-7-acetamido-8-O-acetyl-3,5,7,9-tetradeoxy-nonulos onic acid possessing most likely the D-glycero-L-galacto configuration, representing the first example of an acidic homopolymer of a higher sugar of this class. The ladder-like banding pattern exhibiting small distances between individual bands in the SDS/PAGE is compatible with a monosaccharide repeating unit. [ABSTRACT FROM AUTHOR]

A pentaacyl precursor of lipid A biosynthesis, termed precursor Ib, and a structural isomer have been chemically synthesized. These compounds were, in comparison to synthetic Escherichia-coli type lipid A or lipopolysaccharide, analyzed for their activity in typical endotoxin test systems. It was found that both precursor I b and the isomer exhibited similar or only slightly lower pyrogenic, lethal and Shwartzman-phenomenon-inducing activity than lipid A. All preparations were comparable in their B-lymphocyte mitogenicity, macrophage- activating capacity and immunoreactivity towards lipid A antisera. The proton nuclear magnetic resonance spectra of the 1-dephospho derivative of synthetic and bacterial precursor Ib were indistinguishable proving that the previously proposed structure for precursor Ib is correct. [ABSTRACT FROM AUTHOR]

A 3-deoxyladylosonic acid, not previously described, was identified as a component of the lipopolysaccharide of Acinetobacter calcoaceticus NCTC 10305: 2-keto-3-deoxy-1,7-dicarboxylheptonic acid. This compound, whose steric configuration has not been determined, was released from lipopolysaccharide after acid hydrolysis as monosaccharide and in the form of a glucose-substituted disaccharide. It was identified by combined gas-liquid chromatography/mass spectrometry using various derivatization procedures. The presence of a 2-keto-3-deoxyaldulosonic acid was established from the typical fragmentation pattern of C1-C6 moiety which was identical to that of similarly derivatized authentic 2-keto-3-deoxy-D-mannooctonic acid (dOclA). Location of the keto and deoxy function at C2 and C3, respectively, was deduced from the fragmentation pattern of the deuterolabelled derivatives after reduction of the keto and carboxy groups. The presence of two carboxy groups was ascertained after carboxy reduction with sodium boro-(²H)hydride of the carbonyl-reduced and permethylated derivate whereby the molecular masses were found to differ by 4 Da. Further proof for the presence of two carboxy groups was obtained by alkaline transesterification of the carbonyl-reduced and permethylated derivative with ethanolic sodium ethylate: it was shown that two methyl ester groups had been transesterified since the molecular mass was shifted higher by 28 kDa. Substitution by a D-glucopryranosyl residue in position 4 was established by methylation analysis performed on the carbonyl- and carboxyl-reduced and permethylated disaccharide. The D-configuration of the glucosyl residue was determined by its reactivity with D-glucose oxidase. Thus, the structure of the disaccharide is 4-O-glucopyranosyl-2-keto-3-deoxy-1,7-dicarboxyheptonic acid. [ABSTRACT FROM AUTHOR]

After mild acid hydrolysis, a disaccharide of 3-deoxy-D-manno-octulosonic acid (dOclA) was obtained from Re-mutant lipopolysaccharide of Salmonella minnesota, Salmonella godesberg, Proteus mirabilis, and Escherichia coli, and from the lipopolysaccharide of an S. minnesota Rb2 mutant. Combined gas-liquid chromatography/ mass spectrometry of the reduced and permethylated derivatives indicated that the disaccharide is interlinked by a 2→4-glycosidic bond in all lipopolysaccharides tested. In addition, it was shown by gas-liquid chromatography of appropriate synthetic standards and a previously characterized α2→4-linked dOclA disaccharide (derived from lipopolysaccharide of S. godesberg) that the non-reducing dOclA residue possesses the α configuration. In the case of lipopolysaccharide of S. minnesota Rb2 mutant, this result, together with earlier findings, suggests that it contains a linear dOclA trisaccharide of the sequence doclA(α2-4)dOclA(α2-4)dOclA. The results show that a dOclA(α2-4)dOclA disaccharide represents a common architectural principle in enterobacterial lipopolysaccharides. [ABSTRACT FROM AUTHOR]

The chemical structure of the lipid A component of the lipopolysaccharide from Vibrio cholerae95R was studied. After sequential degradation a reduced D-glucosamine disaccharide was isolated from lipid A and, after permethylation, shown by combined gas-liquid chromatography/mass spectrometry to be β1,6-linked. The disaccharide is substituted with a phosphate group, ester-bound to the non-reducing glucosamine (GlcN) residue and a pyrophosphorylethanolamine group (PP-Etn) linked to C-1 of the reducing glucosamine residue. This backbone structure is shown in the following formula: P-GIcN(β1-6)GIcN-1-PP-Etn. The amino groups of the glucosamine disaccharide are substituted by D-3-hydroxytetradecanoic acid; tetradecanoic, hexadecanoic and a D-3-O-(D-3-hydroxydodecanoyl)-dodecanoic acid residue are linked to hydroxyl groups. A similar fatty acid composition was detected in lipopolysaccharides from Inaba, Ogawa and NAG strains of V. cholerae. [ABSTRACT FROM AUTHOR]

L-2-Hydroxytetradecanoic acid was recognized as a characteristic, although minor, constituent of the lipid A component of Salmonella lipopolysaccharides. The 2-hydroxy fatty acid was present in lipid A as an ester, probably bound to the hydroxyl group of some D-3-hydroxytetradecanoic acid residues. A survey of enterobacterial lipopolysaccharides showed that L-2-hydroxytetradecanoid acid was also present in Klebsiella and Serratia strains. It was absent, however, from lipopolysaccharides of other genera of the family including Escherichia, Shigella, Proteus, Enterobacter and Yersinia. This restricted distribution of the 2-hydroxy acid may be of significance for taxonomic studies of bacterial genera. [ABSTRACT FROM AUTHOR]

The chemical structure of the lipid A component of lipopolysaccharides from Chromobacterium violaceum NCTC9694 was studied. Sequential treatment of lipopolysaccharide with alkali, acid, sodium borohydride and hydrazine allowed the isolation of a reduced glucosamine disaccharide. According to methylation studies and enzymic analysis with β-N-acetylglucosaminidase the D-glucosamine residues are β(1→6) linked. The disaccharide carries two phosphate groups, one being linked glycosidically, the other being linked as an ester to the non-reducing glucosamine. Application of a different degradation pathway shows that the ester-bound phosphate group is substituted by a 4-aminoarabinosyl residue and that the glycosidically link phosphate group is substituted by a glucosaminyl residue. Neither the amino nor the hydroxyl groups of both these substituents are acylated. This backbone structure is shown in the following formula: [This equation cannot be represented into ASCII Text]. The amino groups of the central glucosamine disaccharide are substituted by D-3-hydroxy-dodecanoic acid, the hydroxyl groups by dodecanoic, L-2-hydroxydodecanoic and D-3-hydroxy-decanoic acid. [ABSTRACT FROM AUTHOR]

A degradation procedure of lipopolysaccharides was worked out which allows the isolation of the reduced backbone of lipid A in a total yield of between 20 and 30%. This procedure was applied to lipopolysaccharides of S forms (Salmonella minnesota, Shigellaflexneri 5b, Escherichia coli 086, E. coli 0111, Xanthomonas sinensis, Rhodopseudomonas gelatinosa) and R mutants (Salmonella minnesota, Shigella flexneri 5b, E. coli BB9 and E. coli EH 100). Chemical analysis, reaction with β-N-acetyl-glucosaminidase and application of methylation analysis revealed that the lipid A backbone of all strains contains β1′,6-1inked glucosamine disaccharides carrying two phosphate groups, one in glycosidic and one in ester linkage, a structure, identified previously in the Salmonella minnesota Re mutant. [ABSTRACT FROM AUTHOR]

Salmonella infections in naturally susceptible mice grow rapidly, with death occurring only after bacterial numbers in vivo have reached a high threshold level, commonly called the lethal load. Despite much speculation, no direct evidence has been available to substantiate a role for any candidate bacterial components in causing death. One of the most likely candidates for the lethal toxin in salmonellosis is endotoxin, specifically the lipid A domain of the lipopolysaccharide (LPS) molecule. Consequently, we have constructed a Salmonella mutant with a deletion–insertion in its waaN gene, which encodes the enzyme that catalyses one of the two secondary acylation reactions that complete lipid A biosynthesis. The mutant biosynthesizes a lipid A molecule lacking a single fatty acyl chain and is consequently less able to induce cytokine and inducible nitric oxide synthase (iNOS) responses both in vivo and in vitro. The mutant bacteria appear healthy, are not sensitive to increased growth temperature and synthesize a full-length O-antigen-containing LPS molecule lacking only the expected secondary acyl chain. On intravenous inoculation into susceptible BALB/c mice, wild-type salmonellae grew at the expected rate of approximately 10-fold per day in livers and spleens and caused the death of the infected mice when lethal loads of approximately 108 were attained in these organs. Somewhat unexpectedly, waaN mutant bacteria grew at exactly the same rate as wild-type bacteria in BALB/c mice but, when counts reached 108 per organ, mice infected with mutant bacteria survived. Bacterial growth continued until unprecedentedly high counts of 109 per organ were attained, when approximately 10% of the mice died. Most of the animals carrying these high bacterial loads survived, and the bacteria were slowly cleared from the organs. These experiments provide the first direct evidence that death in a mouse typhoid infection is directly dependent on the toxicity of lipid A and suggest that this may be mediated via pro-inflammatory cytokine and/or iNOS responses. [ABSTRACT FROM AUTHOR]

The three-dimensional supramolecular structures and the states of order of the acyl chains of lipid A from different Gram-negative species were investigated at 40°C, high water content (80–90%), and different [lipid A]/[Mg²+] molar ratios using synchrotron radiation X-ray diffraction and Fourier-transform infrared spectroscopy. Measurements were made on free lipid A from Salmonella Minnesota R595, mono- and bi-phosphoryl, as well as those from the non-enterobacterial strains Rhodobacter capsulatus 37b4, Rhodeopseudomonas viridis F, and Rhodocyclus gelatinosus 29⁄1. Parallel to differences in their chemical primary structure, the structural polymorphisms and states or order at 37°C of the non-enterobacterial lipid A were found to be different from those of enterobacterial lipid A. A clear correlation between the supramolecular structure and previously determined biological activities was found. Lipid A with a strong preference for lamellar structures (Rb. Capsulatus and Rp. viridis) are endotoxically inactive and lack cytokine-inducing capacity: the compounds assuming a mixed lamellar/nonlamellar structure (monophosphoryl lipid A with a strong tendency to form non-lamellar invered structures (lipid A from S. Minnesota and Rc. gelatinosus) exhibit full endotoxicity in vitro and in vivo. In contraxst, anti-complementary activity is most pronounced for compounds with lamellar and least expressed for those with inverted structures. The states of order at 37°C vary non-systematically, exhibiting the highest values for lipid A of S. minnesota and the lowest for that of Rc. gelatinosus. We propose to extend the term ‘endotoxic conformation’, which is used to described the conformation of a single lipid A molecule required for optimal triggering of biological effects, to ‘endotoxic supramolecular conformation’ which denotes the particular organization of lipid A aggregates in physiological fluids causing biological activity. [ABSTRACT FROM AUTHOR]

The chemical structure of the saccharide portion of Vibrio parahaemolyticus serotype 012 lipopolysaccharide was studied. Using chemical degradation and modification, as well as methylation analysis in combination with GLC-MS, laser-desorption mass spectrometry and 1H-NMR and 13C-NMR spectroscopy, the carbohydrate backbone of the lipopolysaccharide was characterized as a branched decasaccharide with the following structure: [This symbol cannot be presented in ASCII format] In the native lipopolysaccharide two additional phosphate groups are present and 3-deoxy-D-threo-hexulosonic acid and D-galacturonic acid are bound via acid-labine linkages. [ABSTRACT FROM AUTHOR]

The structure of the lipid A component of lipopolysaccharides isolated from two wild-type strains (Fisher 2 and 7) and one rough mutant (PAC 605) of Pseudomonas aeruginosa was investigated using chemical analysis, methylation analysis, combined gas-liquid chromatography/mass spectrometry, laser-desorption mass spectrometry and NMR spectroscopy. The lipid A backbone was found to consist of a pyranosidic β1,6-linked D- glucosamine disaccharide [β-D-GlcpN-(1 → 6)-D-GlcpN], phosphorylated in positions 4′ and 1. Position 6′ of the β-D-GlcpN-(1 → 6)-D-GlcpN disaccharide was identified as the attachment site of the core oligosaccharide and the hydroxyl group at C-4 was not substituted. Lipid A of the three P. aeruginosa strains expressed heterogeneity with regard to the degree of acylation: a hexaacyl as well as a pentaacyl component were structurally characterized. The hexaacyl lipid A contains two amide-bound 3-O-acylated (R)-3-hydroxydodecanoic acid groups [12:0(3-OH)] at positions 2 and 2′ of the GlcN dissacharide and two ester-bound (R)-3-hydroxydecanoic acid groups [10:0(3- OH)] at positions 3 and 3′. The pentaacyl species, which represents the major lipid A component, lacks one 10:0(3- OH) residue, the hydroxyl group in position 3 of the reducing GlcN residue being free. In both hexa- and penta- acyl lipid A the 3-hydroxyl group of the two amide-linked 12:0(3-OH) residues are acylated by either dodecanoic (12:0) or (S)-2-hydroxydodecanoic acid [12:0(2-OH)], the lipid A species with two 12:0(2-OH) residues, however, being absent. The presence of only five acyl residues in the major lipid A fraction may account for the low endotoxic activity observed with P. aeruginosa lipopolysaccharide. [ABSTRACT FROM AUTHOR]

The chemical structure of Campylobacter jejuni CCUG 10936 lipid A was elucidated. The hydrophilic backbone of the lipid A was shown to consist of three (1 → 6)-linked bisphosphorylated hexosamine disaccharides. Neglecting the phosphorylation pattern, a D-glucosamine (2-amino-2-deoxy-D-glucose) disaccharide [β-D-glucosaminyl(1→6)-D-glucosamine], a hybrid disaccharide of 2,3-diamino-2,3-dideoxy-D-glucose and D-glucosamine [2,3diamino-2,3-dideoxy-β-D-glucopyranosyl-(1 → 6)-D-glucosamine], and a 2,3-diamino-2,3-dideoxy-D-glucose disaccharide were present in a molar ratio of 1:6:1.2. Although the backbones are bisphosphorylated, heterogeneity exists in the substitution of the polar head groups. Phosphorylethanolamine is α-glycosidically bound to the reducing sugar residue of the backbone, though C-1 is also non-stoichiometrically substituted by diphosphorylethanolamine. Position 4' of the non-reducing sugar residue carries an ester-bound phosphate group or is non-stoichiometrically substituted by diphosphorylethanolamine. By methylation analysis it was shown that position 6' is the attachment site for the polysaccharide moiety in lipopolysaccharide. These backbone species carry up to six molecules of ester- and amide-bound fatty acids. Four molecules of (R)-3-hydroxytetradecanoic acid are linked directly to the lipid A backbone (at positions 2, 3, 2', and 3'). Laser desorption mass spectrometry showed that both (R)-3-hydroxytetradecanoic acids linked to the non-reducing sugar unit carry, at their 3-hydroxyl group, either two molecules of hexadecanoic acid or one molecule of tetradecanoic and one of hexadecanoic acid. It also suggested that the (R)-3-(tetradecanoyloxy)-tetradecanoic acid was attached at position 2', whereas (R)-3(hexadecanoyloxy)-tetradecanoic acid was attached at position 3', or at positions 2' and 3'. Therefore, the occurrence of three backbone disaccharides differing in amino sugar composition and presence of a hybrid disaccharide differentiate the lipid A of this C. jejuni strain from enterobacterial and other lipids A described previously. [ABSTRACT FROM AUTHOR]

Lipopolysaccharides, the major amphiphilic components of the outer leaflet of the outer membrane of Gramnegative bacteria, may assume various three-dimensional supramolecular structures depending on molecular properties (e.g. chemical structure) and on ambient conditions (e.g. temperature, concentration of divalent cations). We applied synchrotron small-angle X-ray diffraction to investigate the supramolecular structures of natural and synthetic Escherichia-coli-type lipid A, of lipid A from Salmonella minnesota, and of rough mutant lipopolysaccharides of E. coli and S. minnesota under physiological water content (> 90%) at different temperatures (20, 37, and 55 °C) and at different lipid/divalent cation molar ratios (20:1 to 1:1). We found that in the absence of divalent cations rough mutant lipopolysaccharide and free lipid A form unilamellar structures with the main reflections centered around 4.50 nm for free lipid A, 4.80 nm for Re lipopolysaccharide, and 5.90 nm for Rd1 lipopolysaccharide at 20°C, i.e. below the β↔α acyl-chain-melting transition temperature. Above this temperature, the reflections are shifted to 4.30 nm for free lipid A (at 55 °C), 4.60 nm for Re lipopolysaccharide (at 37 °C), and to 5.50 nm for Rd1 lipopolysaccharide (at 37°C). The addition of divalent cations leads (at lower concentrations, i.e. lipid/cation molar ratios 20:1 to 5:1) to sharper reflections expressing a higher state of order and to a shift of the center of the main reflections lying now at 5.10 nm for free lipid A, 6.40 nm for Re and 7.20 nm for Rd1 lipopolysaccharide at 20°C. At higher concentrations of divalent cations (e. g. lipid/cation molar ratio 1:1), an increasing tendency to form nonlamellar, inverted cubic structures is observed which is indicated by the occurrence of another main periodicity and/or of reflections with spacing ratios 1:√2, 1:√3 of the main periodicity. The tendency to assume inverted cubic structures is only weakly pronounced for rough mutant lipopolysaccharides but dominant for free lipid A even at physiological temperature and divalent cation concentration. [ABSTRACT FROM AUTHOR]

The chemical structure of Bacteroides fragilis NCTC 9343 lipid A was characterized by using conventional chemical procedures, methylation analysis, and laser desorption mass spectrometry. It was found that B. fragilis lipid A consists of a β-D-glucosaminyl-(1–6)-D-glucosaminyl-l-O-phosphate backbone whose hydroxyl groups in positions 4, 4′ and 6′ are free, the latter serving as the attachment site for the polysaccharide component in lipopolysaccharide. This backbone molecule carries up to of five molecules of ester- and amide-bound long chain non-hydroxylated and (R)-3-hydroxy fatty acids. With regard to the distribution of the fatty acids on the lipid A backbone, a considerable heterogeneity was revealed by laser desorption mass spectrometry. Despite this heterogeneity, a major species of B. fragilis lipid A could be defined in which the hydroxyl group at position 3′ of the distal GleN carries (R)-3-hydroxyhexadecanoic acid and the hydroxyl group at position 3 of the reducing GlcN is acylated by (R)-3-hydroxypentadecanoic acid. The amino group of the distal GleN residue carries (R)-3-(13-methyltetradecanoyloxy)-15-methylhexadecanoic acid and that of the reducing GleN group (R)-3- hydroxyhexadecanoic acid. The absence of ester-bound phosphate and ester-linked 3-acyloxyacyl groups, the presence of not more than five acyl residues and the predominance of fatty acids possessing 15–17 carbon atoms are unique features of B. fragilis lipid A which differentiate it from enterobacterial and other lipids A and which are likely to be related to its low endotoxic activity. [ABSTRACT FROM AUTHOR]

Lipopolysaccharides of different wild-type and mutant gram-negative bacteria, as well as synthetic and bacterial free lipid A, were studied for their ability to activate arachidonic acid metabolism in mouse peritoneal macrophages in vitro. It was found that lipopolysaccharides of deep-rough mutants of Salmonella minnesota and Escherichia coli (Re to Rc chemotypes) stimulated macrophages to release significant amounts of leukotriene C4 (LTC4) and prostaglandin E2 (PGE2). Lipopolysaccharides of wild-type strains (S. abortus equi, S. friedenau) only induced PGE2 and not LTC4 formation. Unexpectedly, free bacterial and synthetic E. coli lipid A were only weak inducers of LTC4 and PGE2 production. Deacylated Re-mutant lipopolysaccharide preparations were inactive. However, co-incubation of macrophages with both deacylated lipopolysaccharide and lipid A lead to the release of significant amounts of LTC4 and PGE2, similar to those obtained with Re-mutant lipopolysaccharide. The significance of the lipid A portion of lipopolysaccharide for the induction of LTC4 was indicated by demonstrating that peritoneal macrophages of endotoxin-low-responder mice or of mice rendered tolerant to endotoxin did not respond with the release of arachidonic acid metabolites on stimulation with Re-mutant lipopolysaccharide and that polymyxin B prevented the Re-lipopolysaccharide-induced LTC4 and PGE2 release. Physical measurements showed that the phase-transition temperatures of both free lipid A and S-form lipopolysaccharide were above 37 °C while those of R-mutant lipopolysaccharides were significantly lower (30-35 °C). Thus, with the materials investigated, an inverse relationship between the phase-transition temperature and the capacity to elicit LTC4 production was revealed. [ABSTRACT FROM AUTHOR]

The chemical structure of the lipopolysaccharide of a deep-rough mutant (strain I-69 Rd¯/b¹) of Haemophilus influenzae was investigated. The hydrophilic backbone of lipid A was shown to consist of a β-(1′r,6)-linked D-glucosamine disaccharide with phosphate groups at C-1 of the reducing D-glucosamine and at C-4′ of the non-reducing one. Four molecules of (R)-3-hydroxytetradecanoic acid were found directly linked to the lipid A backbone, two by amide and two by ester linkage (positions 2, 2′ and 3, 3′, respectively). Laser-desorption mass spectrometry showed that both 3-hydroxytetradecanoic acids linked to the non-reducing glucosamine carry tetradecanoic acid at their 3-hydroxyl group, so that altogether six molecules of fatty acid are present in lipid A. The lipopolysaccharide was the first described to contain only one sugar unit linked to lipid A. This, sugar in accordance with a previous report [Zamze et al. (1987) Biochem. J. 245, 583– 587], was shown to be a dOclA phosphate. The phosphate group was found at position 4, but the analytical procedures employed (permethylation and methanolysis followed by gas-Uquid chromatography/mass spectrometry) also revealed dOclA 5-phosphate. Since a cyclic 4,5-phosphate could be ruled out by 31P-NMR, we conclude that, in this lipopolysaccharide, a mixture of dOclA 4- and 5-phosphate is present. By methylation analysis of the dephosphorylated, deacylated and reduced lipopolysaccharide the attachment site of the dOclA was assigned to position C-6′ of the nonreducing glucosamine of lipid A. The anomeric linkages present in the lipopolysaccharide were assessed by ¹HNMR and 13C-NMR of deacylated lipopolysaccharide. The saccharide backbone of this Haemophilus influenzae lipopolysaccharide possesses the following structure: dOcl Apα(2″–6′)GlcNpβ6GlcNpαP. [ABSTRACT FROM AUTHOR]

On short treatment of the lipopolysaccharide of a deep rough mutant of Proteus mirabilis (strain R45) with hydrochloric acid (0.01 M, 10 min, 100°C) a compound was released which, on high-voltage paper electrophoresis, migrated slightly to the cathode (MGlcN = 0.19) and which stained with ninhydrin, alkaline silver nitrate and in the thiobarbituric acid assay. After purification and derivatization, its chemical structure was identified by combined gas-liquid chromatography/mass spectrometry and two-dimensional shift-correlated proton nuclear magnetic resonance spectroscopy as 8-O-(4-amino-4-deoxy-β-L-arabinopyranosyl)-3-deoxy-D-manno-octulosonic acid. This disaccharide was also present in a wild-type strain of P. mirabilis. [ABSTRACT FROM AUTHOR]

Lipopolysaccharide of Acinetobacter calcoaceticus NCTC 10305 was treated with acid (0.1 M HCl, 100°C, 1 h). The product obtained (LPSdegr) was subjected to various modification and degradation procedures including reduction, hydrazinolysis and strong acid hydrolysis. Methylation analysis of purified part structures revealed the presence of a 4′-phosphorylated (β1′-6)-linked D-glucosamine disaccharide (lipid A backbone), which carried in position 6′ a hitherto unknown 2-octulosonic acid (OclA) in highly acid-stable linkage. It was further shown that OclA is substituted in position 5 by a glucose tetramer, the reducing residue of which is phosphorylated. The hydrophilic region of the LPSdegr, could thus be characterized as a phosphorylated heptasaccharide of the following structure:... [ABSTRACT FROM AUTHOR]

Examines the formation and metabolism of leukotriene C4 in macrophages exposed to bacterial lipopolysaccharide. Stimulation of resident mouse peritoneal macrophages to produce leukotriene C4; Synthesis in control cultures; Use of reversed-phase high-performance liquid chromatography, ultraviolet spectrometry and radioimmunoassay; Incubation conditions.

In the present paper laser desorption mass spectrometry (LDMS) was applied to dephosphorylated free lipid A preparations obtained from lipopolysaccharides of Re mutants of Salmonella minnesota, Escherichia coli and Proteus mirabilis. The purpose of this study was to elucidate the location of (R)-3-hydroxytetradecanoic acid and 3-O-acylated (R)-3-hydroxytetradecanoic acid residues which are bound to amino and hydroxyl groups of the glucosamine disaccharide backbone of lipid A. Based on the previous finding from biochemical analyses that the amino group of the nonreducing glucosamine residue (GlcN II) of the backbone carries, in S. minnesota and E. coli, 3-dodecanoyloxytetradecanoic acid and, in P. mirabilis, 3-tetradecanoyloxytetradecanoic acid, a self-consistent interpretation of the LDMS was possible. It was found that: (a) in all three lipids A GlcN II is, besides the amide-linked 3-acyloxyacyl residue, substituted by ester-linked 3-tetradecanoyloxytetradecanoic acid; (b) the reducing glucosamine (GlcN I) is substituted by ester-linked 3-hydroxytetradecanoic acid; (c) the amino group of GlcN I carries a 3-hydroxytetradecanoic acid which is non-acylated in E. coli and which is partially acylated by hexadecanoic acid in S. minnesota and P. mirabilis. In lipids A which were obtained from the P. mirabilis Re mutant grown at low temperature (12°C) LDMS analysis revealed that specifically the one fatty acid bound to the 3-hydroxyl group of amide-linked 3-hydroxytetradecanoic acid at GlcN II is positionally replaced by Δ9-hexadecenoic acid (palmitoleic acid). It appears, therefore, that enterobacterial lipids A resemble each other in that the 3-hydroxyl groups of the two 3-hydroxytetradecanoic acid residues linked to Glecn II are fully acylated, while those of the two 3-hydroxytetradecanoic acid groups attached to Glen I are free or only partially substituted. [ABSTRACT FROM AUTHOR]

It has previously been demonstrated [Eur. J. Biochem. 124, 191–198 (1982) and 137, 15–22 (1983)] that the lipid A component of Salmnonella and Proteus lipopolysaccharides contains amide-linked (R)-3-acyloxyacyl residues. In the present study lipid A of other gram-negative bacteria was analysed for the presence of amide- bound 3-acyloxyacyl residues. It was found that such residues are constituents of all lipid A tested [Agrobacterium tumefaciens, Chromobacterium violaceum, Pseudomonas aeruginosa, Xanthomonas sinensis, Bacteriodes fragilis, Vibrio cholerae, Fusobacterium nucleatum, Rhodospirillum tenue, Acinetobacter calcoaceticus, and Escherichia coli). Amide-linked (R)-3-acyloxyacyl groups, therefore, represent common and ubiquitous structural elements of bacterial lipid A. The composition of 3-acyloxyacyl groups differed considerably among different bacteria. As amide-bound (R)-3-hydroxy fatty acids straight chain and isobranched acyl groups with 10–17 carbon atoms were identified. The most frequently encountered fatty acids, substituting the 3-hydroxyl group of 3-hydroxy fatty acids, were nonhydroxylated straight chain and isobranched acyl residues with 10–17 carbon atoms as well as (S)-2-hydroxy fatty acids with 12 carbon atoms. In some cases, using laser desorption mass spectrometry, the distribution of 3-acyloxyacyl residues over the two available glucosamine amino groups of the lipid A backbone was investigated. [ABSTRACT FROM AUTHOR]

In this study we describe a general method for the detection and characterization of endotoxin-(lipo- polysaccharide, LPS)-binding membrane proteins. In the past, experimental procedures to detect LPS- binding sites on cells were generally performed with chemically modified LPS derivates. Since any modification of a ligand may lead to a modification of its binding characteristics, the results of those studies are controversial. In our assay, cell membrane preparations are treated with free lipid A, the endotoxic center of LPS, in the presence of normal human serum. After binding of lipid A, membrane proteins are solubilizcd by mild detergent treatment without disruption of the lipid A-protein complexes. Addition of anti-(lipid A) mAbs and subsequent adding of protein A agarose lead to the precipitation of complexes of lipid A and its binding proteins. By SDS/PAGE and western blot, these precipitates can be screened for the presence of LPS/lipid A binding proteins. We describe the use of this method for the immuno-coprecipitation of lipid A (or LPS) with an 80 kDa LPS-binding membrane protein (LMP80), which we have previously identified on several human cells. In addition, CD14, the well-known functional LPS receptor on monocytes and macrophages, can be detected. By means of this immuno-coprecipitation approach we could demonstrate binding of either purified LPS preparations or synthetic lipid A to these LPS/lipid A-binding membrane proteins at physiological pH under conditions in which the proteins are in their natural membranous environment. [ABSTRACT FROM AUTHOR]

Synthetic lipid A part structures corresponding structurally to a biosynthetic lipid A disaccharide precursor have been analyzed for endotoxic activity in several systems in vivo and in vitro. It was found that a synthetic β-1,6-linked D-glucosamine disaccharide, which carries four molar equivalents of (R)-3-hydroxyletradecanoyl residues in positions 2, 3, 2' and 3' and phosphoryl groups in positions 1 and 4' (preparation 406), exhibited lethal toxicity, B lymphocyte mitogenicity, the capacity to engender prostaglandin formation in macrophages and to induce endotoxic tolerance, as well as serological lipid A antigenicity. On a weight basis, preparation 406 was of comparable activity to lipid A precursor and bacterial free lipid A. Preparation 406, like lipid A precursor, lacked, however, the ability to induce the local Shwartzman phenomenon and both preparations were of moderate pyrogenicity. Two further synthetic analogues which contained only one phosphoryl group (preparation 404 at C-4', preparation 405 at C-1) showed comparable diminished activity depending on the test system employed, except in the capacity to inactivate complement where they exhibited, in contrast to preparation 406, significant activity. The results show that the endotoxic principle of lipopolysaccharides, as postulated previously is embedded in the lipid A component. Our results also suggest initial conclusions on the structured requirements for the expression of endotoxin activities. [ABSTRACT FROM AUTHOR]

Salmonella minnesota R 595 (Rc) and other Salmonella strains incorporate cis-Δ9-16:1 (paimitoleic acid) at the expense of mainly dodecanoic acid into the lipid-A portion of lipopolysaccharides, when the cells are grown at low temperature (12 °C). It has recently been shown, that in S. minnesota R 595 grown at 37 °C dodecanoic acid is linked to the 3-hydroxyl group of an amide-bound 3-hydroxytetradecanoic acid. The present data suggest, that cis-Δ9-16:1 occupies the same position in lipid A (12 °C). [ABSTRACT FROM AUTHOR]

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. Indo- methacin, 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 lipopoly- saccharide; concomitantly, cellular cAMP levels were increased. Indomethacin was shown to abolish the stimu- lated cAMP formation. Addition to the culture medium of cAMP or dibutyryladenosine 3′,5′-monopbosphate 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 lipopolysaccbaride-elicited col- lagenase synthesis and excretion is mediated sequentially by stimulated production of prostaglandin E2, enhanced adenylate cyclase activity and increased intracellular cAMP levels. [ABSTRACT FROM AUTHOR]

The adsorption constant of the irreversible adsorption of the bacteriophage K3 to Escherichia coli K12 bacteria is strongly dependent on the incubation temperature. Two inflection points are observed in an Arrhenius plot. For cells grown at 37°C the inflection points are found at 20°C and 28°C whereas these inflection points shift to 10°C and 19°C for cells grown at 12°C. To study the lipid environment of the receptor the temperature dependence of the inactivation of bacteriophage K3 was measured in vitro in the presence of various lipids. The Arrhenius plots of the rate of inactivation of phage K3 by complexes of protein d and lipopolysaccharide are very similar to those observed for whole cells. With lipopolysaccharide isolated from cells grown at 37°C inflection points are observed at 20°C and 28°C. With lipopolysaccharide from cells grown at 12°C the inflection points are found at 10°C and 21°C. These results show that the environment of protein d in vivo can be mimicked perfectly in vitro by protein d/lipopolysaccharide complexes. The fatty acid composition of lipopolysaccharide isolated from cells grown at 37°C and at 12°C differs in that in the latter case the amounts of mono-unsaturated fatty acids (mainly palmitoleic acid) are increased at the expense of lauric acid. This difference in fatty acid composition probably explains the difference in the phase transition temperatures caused by the two lipopolysaccharide preparations. A transition at the inflection point of the highest temperature is also found for lipopolysaccharide using light-scattering measurements and appears to be a thermal transition, since it is also observed in differential scanning calorimetry. [ABSTRACT FROM AUTHOR]

A number of lipopolysaccharides derived from Salmonella and Escherichia coli S and R mutant strains were tested for toxicity and anticomplementary activity in the absence of added antiserum. Although all preparations were toxic, only a few exhibited high anticomplementary activity, while others proved to be of low or negligible activity. It was found that isolated lipid A from both active and reactive lipopolysaccharides was strongly anticomplementary as well as toxic, when made water-soluble with the aid of suitable carriers. Treatment of R form lipopolysaccharide with Mg2+ or Ca2+ led to complete precipitation of the lipopolysaccharide with consequent loss of toxicity and anticomplementary activity. This treatment had practically no effect on the anticomplementary activity and toxicity of S form lipopolysaccharides. When lipopolysaccharide, after reaction with complement, was reisolated and purified, the resulting preparation was found to be non-toxic and of negligible anticomplementary activity. No detectable alterations in either the sugar or the fatty acid composition could be detected. The only significant change was the loss of solubility in water. Treatment of the reisolated lipopolysaccharide with EDTA completely restored solubility m water, toxicity, and anti-complementary activity. [ABSTRACT FROM AUTHOR]

Lipid A preparations from the lipopolysaccharides of four Salmonella minnesota R mutants and one Escherichia coli 0100 R mutant were assayed as soluble complexes with bovine serum albumin for lethality in mice, pyrogenicity in rabbis and complement inactivation. Although generally less active than endotoxic lipopolysaceharides, these lipid · albumin complexes nevertheless exhibited strong biological activity. These results indicate that lipid A contains the endotoxic principle of bacterial lipopolysaccharides. [ABSTRACT FROM AUTHOR]

Lauric, myristic, palmitic, and 3-D-(—)-myristic acid in a ratio of about 1:1:1:3 are present in the lipid A part of the glycolipid derived from the Re mutant Salmonella, minnesota R595. An additional fatty acid, Δ2-tetradecenoic acid found in larger amounts after alkaline treatment was recognized as an artifact formed by a β-elimination reaction from ester-linked 3-myristoxymyristic acid. Various methods for the stepwise liberation of fatty acids were used to identify their distribution on the backbone of lipid A which consists β-1,6-linked glucosamine disaccharide units substituted at position 3' with 2-keto-3-deoxyoctonate acid at positions 1 and 4' with phosphate. It was found that the amino groups of the glucosamine residues are substituted by 3-D.(—)-hydroxymyristic acid whose hydroxyl group is free. The three available hydroxyl groups at positions 3, 4, and 6' of the glucosamine disaccharide are substituted by equal amounts of lauric, palmitic, and 3-D-myristoxymyristic acid and, possibly, by smaller amounts of myristic and unsubstituted 3-D-hydroxymyristic acid. A similar structure of lipid A seems to exist in lipopolysaccharides of other Salmonella species. [ABSTRACT FROM AUTHOR]

The chemical structure of the lipopolysaccharide of a deep-rough mutant (strain I-69 Rd¯/b¹) of Haemophilus influenzae was investigated. The hydrophilic backbone of lipid A was shown to consist of a β-(1′r,6)-linked D-glucosamine disaccharide with phosphate groups at C-1 of the reducing D-glucosamine and at C-4′ of the non-reducing one. Four molecules of (R)-3-hydroxytetradecanoic acid were found directly linked to the lipid A backbone, two by amide and two by ester linkage (positions 2, 2′ and 3, 3′, respectively). Laser-desorption mass spectrometry showed that both 3-hydroxytetradecanoic acids linked to the non-reducing glucosamine carry tetradecanoic acid at their 3-hydroxyl group, so that altogether six molecules of fatty acid are present in lipid A. The lipopolysaccharide was the first described to contain only one sugar unit linked to lipid A. This, sugar in accordance with a previous report [Zamze et al. (1987) Biochem. J. 245, 583– 587], was shown to be a dOclA phosphate. The phosphate group was found at position 4, but the analytical procedures employed (permethylation and methanolysis followed by gas-Uquid chromatography/mass spectrometry) also revealed dOclA 5-phosphate. Since a cyclic 4,5-phosphate could be ruled out by 31P-NMR, we conclude that, in this lipopolysaccharide, a mixture of dOclA 4- and 5-phosphate is present. By methylation analysis of the dephosphorylated, deacylated and reduced lipopolysaccharide the attachment site of the dOclA was assigned to position C-6′ of the nonreducing glucosamine of lipid A. The anomeric linkages present in the lipopolysaccharide were assessed by ¹HNMR and 13C-NMR of deacylated lipopolysaccharide. The saccharide backbone of this Haemophilus influenzae lipopolysaccharide possesses the following structure: dOcl Apα(2″–6′)GlcNpβ6GlcNpαP. [ABSTRACT FROM AUTHOR]