Galactosamine-induced sensitization to the lethal effects of endotoxin

Immunobiologically active lipid A analogs synthesized according to a revised structural model of natural lipid A

Synthetic lipid A analogs which have two amide-bound and two ester-bound (R)-3-hydroxytetradecanoyl groups at the C-2 and -2' and C-3 and -3' positions of beta(1-6)glucosamine disaccharide mono- or diphosphates showed high activities in most in vitro assays, and the lethality of a diphosphate derivative to galactosamine-treated mice was almost comparable to that of natural lipid A. The pyrogenicity and Shwartzman induction activity of the synthetic analogs, however, were much less than those of natural lipid A.

Biological activities of synthetic lipid A analogs: pyrogenicity, lethal toxicity, anticomplement activity, and induction of gelation of Limulus amoebocyte lysate

Chemically synthesized lipid A analogs were investigated for several endotoxic activities, including pyrogenicity, lethal toxicity, anticomplement activity, and the capacity to gelate Limulus amoebocyte lysate in comparison to natural lipid A. The synthetic preparations contained D-glucosamine or D-glucosamine-beta-1,6-D-glucosamine disaccharide substituted by ester- and amide-bound hydroxylated or non-hydroxylated fatty acids and by phosphate groups in different combinations. Some preparations which were insoluble in water were succinylated and thus rendered more soluble. Strong biphasic pyrogenic responses with a maximal increase in body temperature of 1 to 2 degrees C were obtained with 50 micrograms/kg doses of 3 disaccharide preparations of 15 tested. With two preparations (50 micrograms/kg) moderate pyrogenicity with monophasic fever curves and a maximal temperature increase of about 0.6 degrees C was obtained. Lethal toxicity tests were carried out in galactosamine-sensitized mice. Of 15 synthetic preparations, 4 exhibited lethal toxicity under these conditions. The effective doses of the lipid A analogs in both in vivo tests were, however, several hundred times higher than those of bacterial lipid A. For the activities in vivo, hydroxyacyl residues seemed to be important. Anticomplement activity was demonstrable in seven preparations, one of which expressed an activity comparable to that of lipid A. Preparations containing non-hydroxylated fatty acids seemed to be most active in this test. None of the synthetic preparations was found to exhibit gelation activity for Limulus amoebocyte lysate when tested in doses up to 0.4 micrograms, whereas bacterial free lipid A was active in doses of about 2 pg. None of the monosaccharide derivatives exhibited any of these activities.

Endotoxic properties of chemically synthesized lipid A part structures. Comparison of synthetic lipid A precursor and synthetic analogues with biosynthetic lipid A precursor and free lipid A

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 beta-1,6-linked D-glucosamine disaccharide, which carries four molar equivalents of (R)-3-hydroxytetradecanoyl 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 or 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 structural requirements for the expression of endotoxin activities.

Nontoxic lipopolysaccharide from Rhodopseudomonas sphaeroides ATCC 17023

Chemical analysis of the lipopolysaccharide from Rhodopseudomonas sphaeroides ATCC 17023, isolated by the phenol-chloroform-petroleum ether method, revealed the presence of glucuronic acid, 2-keto-3-deoxyoctonate, threonine, and phosphorus in the polysaccharide moiety. The lipid A component contained glucosamine, glucosamine phosphate, amide-bound 3-oxotetradecanoic acid and 3-hydroxytetradecanoic acid, and ester-bound 3-hydroxydecanoic acid and 7-tetradecenoic acid. Structural similarity of the lipid A from R. sphaeroides ATCC 17023 to enterobacterial lipid A is indicated by the existence of a serological cross-reaction occurring between the lipid A from R. sphaeroides ATCC 17023 and that from Salmonella minnesota R595. The lipopolysaccharide and lipid A of R. sphaeroides, however, were found to be neither toxic in mice nor pyrogenic in rabbits.

Lipopolysaccharides of two strains of the phototrophic bacterium Rhodopseudomonas capsulata

The lipopolysaccharides of Rhodopseudomonas capsulata strains St. Louis (ATCC 23782) and Sp 11 both contain L-acofriose, rhamnose, glucose and glucosamine as the main sugar constituents. 2-Keto-3-deoxyoctonate and neuraminic acid were tentatively identified. The fatty acid spectrum found with both strains comprises 3-OH-C10 and C12:1 (ester-linked) and 3-oxo-C14 (amide-linked). Isolated lipid A from strain Sp 11 contains glucosamine, glucosamine-phosphate and the total of the fatty acids of the lipopolysaccharide. Methylation analysis of the degraded polysaccharide of this lipopolysaccharide shows L-acofriose in both terminal and 1 leads to 2 chain-linked positions in a 1:4 molar ratio. Rhamnose is exclusively chain-linked (1 leads to 2), glucose is both terminally and chain-linked (1 leads to 6) in a 1:1 molar ratio. The serological activity of the lipopolysaccharide of both the R. capsulata strains is low in antisera against living or heat-killed cells when tested by passive hemagglutination, Ouchterlony immunoprecipitation or gel-immunoelectrophoresis. No crossreaction was observed among the lipopolysaccharides of R. capsulata strains St. Louis, Sp 11 and 37b4 in immunoprecipitation. Lipopolysaccharide of strain Sp 11 was found to lack lethal toxicity in galactosamine-sensitized mice.

Reversible inhibition of RNA synthesis and irreversible inhibition of protein synthesis by D-galactosamine in isolated mouse hepatocytes

The inhibition of RNA synthesis of isolated mouse liver parenchymal cells caused by 10 mM D-galactosamine was reversible, while the inhibition of protein synthesis remained unaltered after the removal of galactosamine. 10(-5)M epinephrine and 10(07)M glucagon have been shown to decrease aminoglycogen formation and thus to reduce the inhibitory effect of galactosamine on protein synthesis (II). However, these hormones did not decrease the inhibition of RNA synthesis. 10 mM D-galactosamine did not effect the nucleoside and amino acid incorporation of isolated non-parenchymal mouse liver cells. The predominant role of aminoglycogen in the inhibition of protein synthesis in galactosamine induced liver injury is discussed.

Endotoxin-induced hyperinsulinemia and hyperglucagonemia after experimental liver injury

Basal portal and systemic venous hyperinsulinemia and hyperglucagonemia were present in fasted rats at 24 h after experimental liver injury by partial (67%) hepatectomy, carbon tetrachloride gavage, and intravenous D-galactosamine administration. Both enhanced pancreatic hormone secretion and depressed hepatic hormone extraction were likely responsible for the insulin and glucagon oversupply. Endogenous gut-derived endotoxin is proposed as the causative factor for the exaggerated hormonal response because intravenous exogenous endotoxin elicited an identical elevation of insulin and glucagon. Systemic endotoxemia at 24 h after liver injury was indicated by marked (78-100%) lethality in lead-sensitized rats and positive Limulus lysate gelation tests of plasma samples. Furthermore, antiendotoxin treatments, including endotoxin tolerance, polymyxin B, and gut sterilization, significantly reduced both lead-sensitized lethality and hyperinsulinemic and hyperglucagonemic responses at 24 h in most liver-injury groups. Portal versus systemic venous administration of endotoxin at a low dose implied that normal endotoxin phagocytosis by the liver suppressed the pancreatic endocrine response. A physiological negative-feedback control system involving gut-derived systemic endotoxemia after liver damage with insulin and glucagon hypersecretion by the pancreas for stimulation of hepatic regeneration is hypothesized.