Endotoxic glycolipid as a potent depressor of the hepatic drug-metabolizing enzyme systems in mice

Factors involved in the down-regulation of cytochrome P450 during Listeria monocytogenes infection

The activation of host defense mechanisms has been shown to cause a depression in hepatic cytochrome P450-mediated metabolism in rodents and humans. In a previous study, it was demonstrated that the Gram-positive bacteria Listeria monocytogenes causes a down-regulation of hepatic cytochrome P450 and related substrate metabolism as a result of a pretranslational depression of apoprotein synthesis. The objectives of this study were to determine whether the effect of listeria on hepatocyte cytochrome P450 involves hepatic nonparenchymal cells and whether the hemolysin, secreted only by hemolytic forms of the bacteria, plays any part in mediating this effect. Total cytochrome P450 levels as well as ethoxyresorufin-O-dealkylase (EROD) and benzyloxyresorufin-O-dealkylase (BROD) activities were significantly reduced in hepatic microsomes isolated from mice infected in vivo for 48 h with 15U listeria, whereas the same dose of the avirulent non-hemolytic M3D strain had no effect. Listeria (15U) significantly depressed hepatocyte EROD and BROD activities after 24 h incubations with liver cell cultures containing hepatocytes and nonparenchymal cells, as the result of both a direct effect on the hepatocyte and an interaction of listeria with hepatic nonparenchymal cells. The M3D strain of listeria had no effect on cytochrome P-450-mediated metabolism in isolated cells, confirming that hemolysin is an essential component of the mechanism responsible for the down-regulation of cytochrome P450 during listeria infections.

Neutralization of Shwartzman-inducing activity by antibodies recognizing the Re core or lipid A structures of lipopolysaccharide from Salmonella minnesota R595 and Pseudomonas vesicularis JCM1477

Antibodies recognizing the Re core or lipid A structures of lipopolysaccharide (LPS) derived from Salmonella minnesota R595 and Pseudomonas vesicularis JCM1477 were tested for the ability to neutralize the preparatory activity of endotoxin using the local Shwartzman reaction. Shwartzman-inducing activity of R595 LPS (Re-form) was strongly suppressed when the LPS was incubated with the rabbit anti-R595 antiserum or the purified IgG antibody which recognizes core region of the LPS. The antiserum also suppressed the preparatory activity of LPS from S. typhimurium SL1102 (Re) and Escherichia coli F515 (Re), but not that of either S. typhimurium LT-2 (S) LPS or R595 lipid A. Moreover, it was found that the murine monoclonal antibody (MAb), SmRe100G (IgG2a) which recognizes the core region of R595 LPS, significantly suppressed the preparatory activity of R595 LPS. Both conventional antibodies specific to R595 lipid A, which contains a 1,4'-bisphosphorylated beta-D-glucosaminyl-alpha-D-glucosamine disaccharide structure, and JCM1477 lipid A, which contains a monophosphorylated 3-amino-D-glucosamine disaccharide structure, neutralized the preparatory activity of homologous and a closely related lipid A, but not that of LPS. In addition, it was observed that MAb Sm5G (IgG2b) specific to enterobacterial lipid A preparations (especially R595 lipid A) neutralized the preparatory activity of R595 lipid A, although the effect was somewhat weak as compared with that of rabbit antiserum. These results suggest that anti-Re LPS antibody binding to the core of Re LPS is involved in suppressing the endotoxic activity of Re LPS, and that the direct binding of anti-lipid A antibody to some specific epitopes of lipid A is important in neutralizing the endotoxic activity.

Structural heterogeneity regarding local Shwartzman activity of lipid A

The relation of chemical structure to local Shwartzman activity of lipid A preparations purified by thin-layer chromatography from five bacterial strains was examined. Two lipid A fractions from E. coli F515--Ec-A2 and Ec-A3--exhibited strong activity, similar to that of previous synthetic E. coli-type lipid A (compound 506 or LA-15-PP). The Ec-A3 fraction contained a component that appeared to be structurally identical to compound 506, and the main component of Ec-A2 fraction was structurally similar to compound 506 except that it carried a 3-hydroxytetradecanoyl group at the C-3' position of the backbone in place of a 3-tetradecanoyloxytetradecanoyl group. Free lipid A (12 C) and purified lipid A fractions, Ec-A2 (12 C) and Ec-A3 (12 C), respectively, obtained from bacteria grown at 12 C, exhibited activity comparable to Ec-A2 or Ec-A3. In these preparations, a large part of the 3-dodecanoyloxytetradecanoyl group might be replaced by 3-hexadecenoyloxytetradecanoyl group. Salmonella minnesota R595 free lipid A also contained at least two active lipid A components as seen in E. coli lipid A, but the third component corresponding to the synthetic Salmonella-type lipid A (compound 516 or LA-16-PP) exhibited low activity. A lipid A fraction, Cv-A4 from Chromobacterium violaceum IFO 12614, which was proposed to have two acyloxyacyl groups at the C-2 and C-2' positions with other acyl groups, exhibited weaker activity than the free lipid A or LPS. The purified lipid A fractions from Pseudomonas diminuta JCM 2788 and Pseudomonas vesicularis JCM 1477 contained an unusual backbone with 2,3-diamino-2,3-dideoxy-D-glucose disaccharide phosphomonoester, and these lipid A (Pd-A3 and Pv-A3) exhibited strong activity comparable to the E. coli lipid A. Thus, the present results show that the local Shwartzman reaction can be expressed by partly different lipid A structures in both hydrophilic backbone and fatty acyl residues; when they have the same backbone the potency varies markedly depending on the structure of the acyl residues.

Pseudomonas diminuta LPS with a new endotoxic lipid A structure

Lipid A that contains mainly 2,3-diamino-2,3-dideoxy-D-glucose, phosphate and fatty acids in the molar ratio 2:1:5-6 was found in Pseudomonas diminuta lipopolysaccharide. The lipid A was considered to have a diamino-sugar disaccharide structure that carries a nonglycosidic phosphomonoester group and amide-bound acyloxyacyl and 3-hydroxy fatty acyl groups. The lipopolysaccharide exhibited endotoxic activities including lethal toxicity, pyrogenicity, local Shwartzman activity, body weight-decreasing toxicity and Limulus activity. The free lipid A was also endotoxic.

Low endotoxic activities of synthetic Salmonella-type lipid A with an additional acyloxyacyl group on the 2-amino group of beta (1-6) glucosamine disaccharide 1,4'-bisphosphate

A synthetic lipid A (Salmonella type, compound 516), beta (1-6)-linked D-glucosamine disaccharide 1,4'-bisphosphate, with three acyloxyacyl groups and one hydroxyacyl group, i.e., (R)-3-hexadecanoyloxytetradecanoyl, (R)-3-hydroxytetradecanoyl, (R)-3-dodecanoyloxytetradecanoyl, and (R)-3-tetradecanoyloxytetradecanoyl groups at the 2-amino, 3-hydroxyl, 2'-amino, and 3'-hydroxyl groups, respectively, was less biologically active than the synthetic Escherichia coli-type lipid A (compound 506), which has only two acyloxyacyl groups at the 2' and 3' positions and is substituted with a (R)-3-hydroxytetradecanoyl group at the 2-amino group. Compound 516 exhibited considerably weaker pyrogenic and leukopenic activity than compound 506, and it scarcely prepared rabbit skin for the Shwartzman reaction and lacked lethal toxicity on chicken embryos, although its lethal toxicity in galactosamine-loaded mice was as strong as that of compound 506. Compound 516 was also less active than compound 506 or natural E. coli lipid A (from Restrain F515) in other biological test systems, such as the Limulus test, stimulation of macrophages and lymphocytes, and interferon-inducing activity but not for interleukin-1 induction or complement activation. This observation suggests that there is an optimal number of acyloxyacyl groups on the glucosamine backbone for producing the biological activities of lipid A, especially the endotoxic activities. The 4'-monophosphate analog (compound 514) of compound 516 in general had significantly weaker activity than compound 516 in the above assays, most probably because of its greater hydrophobicity and consequently lower solubility in assay systems. Bacterial R595 lipid A derived from S. minnesota Re-mutant, which is a mixture of compounds 516 and 506, their 4'-monophosphate analogs and other compounds, exerted intermediate degrees of activity between compounds 506 and 516 in the various test systems employed.

Synthetic Salmonella-type lipid A antigen with high serological specificity

A synthetic compound (compound 516), beta(1-6)-linked D-glucosamine disaccharide 1,4'-bisphosphate, which is acylated by (R)-3-hexadecanoyloxytetradecanoyl, (R)-3-hydroxytetradecanoyl, (R)-3-dodecanoyloxytetradecanoyl, and (R)-3-tetradecanoyloxytetradecanoyl groups at positions 2,3,2', and 3', respectively, exhibited in vitro antigenic reactivity of high specificity comparable to that of free lipid A from Salmonella minnesota R595. This was confirmed by an enzyme-linked immunosorbent assay and an enzyme-linked immunosorbent assay inhibition test with monoclonal and conventional antibodies. The results of comparative analysis performed with several synthetic lipid A analogs as well as three monosaccharide derivatives suggested that the complete structure involving both phosphate groups at the C-1 and C-4' positions and the 3-acyloxyacyl groups at the C-2, C-2', and C-3' positions of the glucosamine disaccharide are required for the expression of the serological specificity of Salmonella-type lipid A. This was deduced from the observations that compound 506, a synthetic Escherichia coli-type lipid A which has the same structure as that of compound 516, except that 3-hydroxytetradecanoyl group is substituted for an acyloxyacyl residue at the C-2 position, exhibited significantly reduced antigenic reactivity as compared with compound 516 and that the replacement by the hydrogen atom of the phosphoryl group at the C-1 position or by 3-hydroxytetradecanoyl or tetradecanoyl groups of acyl residues at the 2, 3, 2', and 3' positions of compound 516 results in a marked reduction of reactivity with monoclonal antibodies 5G and 36G. Similar results were obtained by assays with conventional rabbit antibodies, but the structural difference between compounds 516 and 506 could not be distinguished by these polyclonal antibodies. The results of cross-reactions among synthetic analogs with monoclonal antibodies 161M and 1-9M, which have been confirmed to exhibit different serological specificities from the 5G or 36G antibody, also suggested that the nature and linkage of fatty acyl residues as well as the backbone structure of lipid A play an important role in determining serological specificity of the lipid A molecule.

In vitro antigenic reactivity of synthetic lipid A analogues as determined by monoclonal and conventional antibodies

Cross-reactivities of synthetic lipid A analogues with monoclonal and conventional antibodies against Salmonella lipid A were studied. It was shown that the in vitro antigenicity of a synthetic compound 506, beta-(1----6) D-glucosamine disaccharide 1,4'-bisphosphate, which is acylated at 2'-amino and 3'-hydroxyl groups with (R)-3-dodecanoyloxytetradecanoyl and (R)-3-tetradecanoyloxytetradecanoyl groups, respectively, and has (R)-3-hydroxytetradecanoyl groups at 2-amino and 3-hydroxyl groups, was practically indistinguishable from that of the natural E. coli lipid A preparation, and that both phosphates in positions 1 and 4' as well as ester- and amide-linked fatty acyl residues, particularly 3-acyloxyacyl group, of the glucosamine disaccharide are involved in the cross-reactivity of lipid A as important antigenic determinants.

Induction of tolerance in mice and rats to the effect of endotoxin to decrease the hepatic microsomal mixed-function oxidase system. Evidence for a possible macrophage-derived factor in the endotoxin effect

Daily administration of low, non-lethal doses of bacterial endotoxin to mice and rats has been shown to induce tolerance to the effect of an acute challenge dose of endotoxin to decrease the hepatic microsomal drug metabolizing activity, the level of cytochrome P-450, and to increase heme oxygenase activity. The serum collected at various times after injection of endotoxin into control animals when injected into untreated animals markedly depressed aniline hydroxylase activity, ethylmorphine N-demethylase activity, and the level of cytochrome P-450. Tolerant animals were not affected by the post-endotoxin serum injection, suggesting the decreased activity caused by the serum in untreated animals was probably due to endotoxin contained in the serum. Injection of tolerant mice and rats with supernatant medium obtained from cultures of peritoneal macrophages incubated with 100 micrograms/ml of endotoxin caused a loss of hepatic microsomal drug-metabolizing activity, and a decrease in the level of cytochrome P-450. These results suggest that peritoneal macrophages release a factor in response to endotoxin that mediates the decreased hepatic mixed-function oxidase activity.

Hepatic drug-metabolizing enzyme system and endotoxin tolerance: structural requirement of LPS in induction of an early tolerance

The alteration of hepatic drug-metabolizing enzyme activities in mice given Salmonella endotoxin by single or multiple intraperitoneal injections was investigated. An essentially the same biphasic, early and late phase, endotoxin tolerance was observed in the animals receiving a single injection of endotoxin or repetitive daily injections. The results of reciprocal cross tolerance tests using lipopolysaccharide and free lipid A preparations derived from Salmonella minnesota, Salmonella typhimurium, E. coli, Pseudomonas aeruginosa, and Chromobacterium violaceum suggested that lipid A moiety plays an important role in the induction of early endotoxin tolerance to endotoxin response.

Trifluorinated ether anesthetic lethality in rats: the role of bacterial infection

The lethal effects of the fluorinated ether anesthetics fluroxene (2,2,2-trifluoroethyl vinyl ether) and its ethyl (TFEE) and allyl analogues in male Wistar rats have previously been demonstrated to be potentiated by specific hepatic microsomal cytochromes P-450, and mediated by the common metabolite 2,2,2-trifluoroethanol (TFE). We report here that administration of lethal combinations of anesthetic and cytochrome P-450-inducing agents or of lethal doses of TFE (0.21 g/kg and higher) to rats caused decreased white blood cell counts, necrosis of sternum bone marrow cells and lymphocytes in the thymic cortex, and resulted in Escherichia coli contamination of the blood, lungs, liver, and kidneys of treated rats. Control animals in identical environments were free of bacterial contamination. Pretreatment of rats with the antibiotic tetracycline-HCl in the drinking water (0.6 g/liter) from 24 hr before anesthetic or TFE administration significantly diminished the mortality. With TFEE and beta-naphthoflavone induction, mortality was reduced from 85 to 30% by the antibiotic. However, the antibody plaque assay following immunization with sheep erythrocytes indicated that the primary humoral immune response to a thymus-dependent antigen was not impaired in treated rats. These results considered together indicate that metabolic formation of TFE from the anesthetic agents produced a decreased host resistance with subsequent increased susceptibility to bacterial infection. If not administered the antibiotic, the animals succumbed to the infection.

Immunobiological activities of synthetic lipid A analogs and related compounds as compared with those of bacterial lipopolysaccharide, re-glycolipid, lipid A, and muramyl dipeptide

Thirteen acylated and phosphorylated derivatives of beta-1,6-linked glucosamine disaccharide (lipid A analogs), which were synthesized after the structural model of Salmonella-type lipid A, and seven similar derivatives of glucosamine monosaccharide (lipid A-related compounds) were studied for their immunobiological activities. These included mitogenicity and polyclonal B cell activation enhancement of migration of monocytes and polymorphonuclear leukocytes derived from human peripheral blood, stimulation of guinea pig peritoneal macrophages, activation of human complement, and stimulation of serum antibody production and induction of delayed-type hypersensitivity against ovalbumin in guinea pigs. Comparisons were made with lipid A, RE-glycolipid, lipopolysaccharide of natural sources, and a well-known synthetic adjuvant, N-acetylmuramyl-L-alanyl-D-isoglutamine. Some of the lipid A analogs were found to manifest the mitogenic, polyclonal B cell-activating macrophage-stimulating, complement-activating, and immunostimulating activities, although the observed activities were generally far less than those of natural products in intensity and efficiency. Other immunobiological effects exhibited by most of the synthetic lipid A analogs were the enhancement of migration of monocytes and polymorphonuclear leukocytes. It is premature to draw definite conclusions on structure-activity relationships, since a few compounds which were active in some assay systems were scarcely active in other assays. However, an indisputable fact was that beta-1,6-glucosamine disaccharide 1 alpha,4'-diphosphate, which carries two amide-bound (R)-3-hydroxytetradecanoyl and three ester-bound tetradecanoyl residues, and thus has the structure most closely resembling natural lipid A among test compounds in this study, was definitely active in all of the present assay systems. However, its potency was generally much less than natural products. Some of glucosamine monosaccharide derivatives, especially N-(R)-3-[(R)-3-hydroxytetradecanoyloxy]tetradecanoyl glucosamine, also exerted all of the in vitro activities described above. This fact suggests that a glucosamine disaccharide structure may not necessarily be a prerequisite as far as the in vitro immunobiological activities tested are concerned.

Effect of endotoxin and its degradation products on hepatic mixed-function oxidase and heme enzyme systems in mice

Effect of Salmonella minnesota R595 endotoxin (R595 GL) and its chemical degradation products on hepatic cytochrome P-450, delta-aminolevulinic acid (ALA) synthetase and heme oxygenase activity in mice was examined. The levels of cytochrome P-450 and ALA synthetase activity were significantly decreased following the administration of R595 GL, whereas heme oxygenase activity was markedly increased. The effects of endotoxin were dose-dependent for the range of about 1 to 2 micrograms per mouse. The result of a comparative study using R595 GL and its degradation products suggested that intact lipid A moiety plays an important rôle in the activity of endotoxin. In addition, it was found that the depressant effect of endotoxin on the hepatic mixed-function oxidase system in mice was abrogated by treatment with cortisone.