Galactosamine-induced sensitization to the lethal effects of endotoxin

Dynamics of bacterial translocation in acute liver injury induced by D-galactosamine in rat

Bacterial translocation may play a role in acute liver injuries as high rates of infectious and septic complications are observed in these clinical conditions. Increased passage of endotoxin and translocating bacteria not only potentiates the extent of liver injury, but may also play a determining role in its final outcome. In this paper the incidence of bacteria] translocation in acute liver injury in rats is evaluated with other important pathological changes observed at different time points after liver injury induced by intraperitoneal administration of D-galactosamine. The bacterial translocation to the blood and other extraintestinal sites starts 3 h after induction of liver injury and is not found to be related to light microscopic changes in the liver or ileal or cecal mucosa, detectable levels of endotoxin in the portal blood, or DNA changes in the small and large intestinal mucosa, but corresponds to the release of liver enzymes in the serum.

Sinusoidal lining cells and hepatotoxicity

Treatment of experimental animals with toxic doses of acetaminophen, carbon tetrachloride, phenobarbital, galactosamine, or endotoxin results in an accumulation of macrophages in the liver. These mononuclear phagocytes, as well as hepatic endothelial cells and stellate cells, are activated to release increased amounts of proinflammatory and cytotoxic mediators including hydrogen peroxide, superoxide anion, nitric oxide, bioactive lipids, interleukin 1, platelet activating factor, and tumor necrosis factor alpha. Each of these mediators has the capacity to induce tissue injury directly and/or augment the inflammatory response. When animals are treated with agents that block macrophage functioning and/or mediator release, xenobiotic-induced hepatotoxicity is reduced. In contrast, treatment of animals with macrophage activators augments toxicant-induced liver damage. These data provide direct support for a role of macrophages and inflammatory mediators in hepatotoxicity.

Comparison of the biological activity of synthetic N-acylated asparagine or serine linked monosaccharide lipid A analogs

The mitogenicity, lethal toxicity, induction of tumor necrosis factor (TNF), production of nitric oxide (NO) and antitumor activity against Meth A fibrosarcoma by chemically synthesized N-acylated asparagine-linked (A-701, A-702 and A-703) or N-acylated serine-linked (A-607) nonphosphorylated acylglucosamine and 4-0-phosphorylated acylglucosamine (A-103) derived lipid A analogs were determined. compound A-607 (with tetradecanoyl and (R)-3-tetradecanoyloxytetradecanoyl at the C-2 and C-3 positions) induced a significant incorporation of 3H-thymidine into splenocytes of C3H/He mice at concentrations ranging from 3.13 to 50 microM, but the mitogenic activity of A-701 (2-N-acetylglucosamine), A-702 (tetradecanoyl at the C-2), and A-703 (with (R)-tetradecanoyloxytetradecanoyl and tetradecanoyl at the C-2 and C-3) was very weak. The lethality of A-703 and A-103 (with (R)-3-tetradecanoyloxytetradecanoyl at the C-2 and C-3) was weaker than that of A-607 at doses of 300 and 750 nmol/kg in C57BL/6 mice loaded with D-galactosamine. Peritoneal macrophages, stimulated with A-701-A-703, caused production of TNF which induce L929 cell lysis in vitro, and A-703 showed a high production of TNF. The compounds, except for A-607, exhibited little NO production by macrophages, but did induce the NO production in the presence of interferon gamma. Induction of TNF and NO inducible activity by A-703 was lower than that of A-607. A-703, A-607 and A-103 showed antitumor activity against Meth A fibrosarcoma in BALB/c mice. When A-703 or A-103 with muramyl dipeptide was administered, A-703 failed to show combined effects, but A-103 did. We concluded from these findings that the biological potency of asparagine compounds appears to be placed between serine- and amino-free compounds.

Prevention of endotoxin-induced acute lethality in Propionibacterium acnes-primed rabbits by an antibody to leukocyte integrin beta 2 with concomitant reduction of cytokine production

Acute lethality was induced in rabbits by the sequential injection of Propionibacterium acnes and lipopolysaccharide (LPS). P. acnes induced the infiltration of inflammatory cells into the liver lobules during the early phase, and LPS in the late phase caused death in association with pathological changes mimicking hepatocellular necrosis or degeneration around infiltrated mononuclear cells and fibrin deposition in the liver, lung, and kidney, suggestive of a systemic Schwartzman-like reaction. These pathological changes were accompanied by the elevation of plasma tumor necrosis factor (TNF) and interleukin-8 (IL-8) levels. A neutralizing antibody to a leukocyte adhesion molecule, integrin beta 2 (CD18), administered at the time of LPS challenge, prevented reduced the elevation of plasma TNF and IL-8 levels. An anti-TNF alpha antibody but not an anti-IL-8 mediator in this model. These results indicate that CD18 is critically involved in vivo in activating leukocytes to produce cytokines in response to LPS.

Quantitation and biological properties of released and cell-bound lipooligosaccharides from nontypeable Haemophilus influenzae

Nontypeable Haemophilus influenzae (NTHi) is a major pathogen causing otitis media in children. NTHi releases lipooligosaccharide (LOS) as outer membrane fragments during its growth. The release of LOS may play an important role in the pathogenicity of otitis media caused by this organism. The amounts of LOS in bacterial cells and growth media for five NTHi strains were determined by quantitative silver staining after sodium dodecyl sulfate-polyacrylamide gel electrophoresis. These strains were estimated to have 1.6 x 10(6) to 4.8 x 10(6) LOS molecules per bacterium. During a 3-day growth period, these NTHi strains released variable but significant amounts of LOS into the growth medium. Cells started to release detectable amounts of LOS into the medium at 2 to 5 h and continued to do so for up to 48 or 72 h. The concentrations of LOS in the culture supernatants released by these five strains were 10 to 55 micrograms/ml at 24 h and 40 to 100 micrograms/ml at 72 h, which was 34 to 189% of the cell-bound LOS concentration. The biological properties of released and cell-bound LOSs from two representative strains were compared. Released LOS showed an approximately 10-fold increase in inducing human monocytes to produce tumor necrosis factor alpha, interleukin 1 beta, and interleukin 6, a 13- to 28-fold increase in mouse lethal toxicity, and a 16- to 37-fold increase in the clotting of Limulus amebocyte lysate. These results suggested that released LOS or its inflammatory mediators play a more important role than the LOS in bacteria in the pathogenicity of otitis media caused by this organism.

Comparative virulence of periodontopathogens in a mouse abscess model

OBJECTIVE(S)

This report compares the virulence of selected strains of P. gingivalis, A. actinomycetemcomitans, C. rectus, F. nucleatum and T. denticola in a murine model as a measure of pathogenic potential of these oral microorganisms. The characteristics of the tissue destruction associated with these monoinfections were then related to a potential model for bacterial synergism in progressing periodontitis.

DESIGN AND METHODS

All bacterial strains were grown to mid-logarithmic to early stationary growth phase, harvested and used at various doses to challenge BALB/c normal and BALB/c dexamethasone (DEX) treated mice to mimic a neutrophil dysfunction. The characteristics of tissue destruction, and overt tissue destructive capacity of these species were examined as a function of challenge dose and time.

OUTCOME MEASURES

The mice were examined for an interval of approximately 15 days post-challenge and the presence/absence of lesions, localized or generalized nature of the lesion (including size in mm2), and lethality of the infection were assessed.

RESULTS

Comparison of the virulence of the various P. gingivalis strains related to lethality and lesion size associated with destruction of the connective tissue, indicated a virulence capacity of P. gingivalis strains 53977>W50 = T22>3079>33277>381. C. rectus elicited localized necrotic lesions which were limited to the epithelial layers of the skin. The size of the lesions also indicated a graded difference in virulence, such that C. rectus strains 234>576>>33238. A. actinomycetemcomitans caused the formation of classic localized abscesses with a PMN infiltrate and inflammatory exudates. Although each of the A. actinomycetemcomitans strains exhibited a similar virulence pattern in this murine model, A. actinomycetemcomitans serotype b representative strains were potentially more pathogenic with a virulence capacity of 3113D-N = 3975A>JP2 > or = Y4>29523>33384. Both C. rectus and A. actinomycetemcomitans strains showed clear evidence that recent clinical isolates were more virulent than laboratory strains. Challenge with F. nucleatum resulted in tissue destructive responses which were different from those observed with the other strains used in this study. A rapid onset of dose-dependent lesion development, related to the formation of either closed abscesses or open lesions, was observed with F. nucleatum. Tissue involvement was also greater at lower F. nucleatum doses when compared to the other bacteria. F. nucleatum challenge of DEX-treated mice resulted in a shift to open lesions. T. denticola appeared to be more tissue invasive than the other species examined in this study. Challenge of mice with T. denticola resulted in involvement of multiple tissues, including epithelial and connective tissues, as well as appearing to invade muscle layers and deeper tissues. In addition to invading deeper tissues, the resulting lesions took considerably longer to resolve. In the DEX-treated mice (neutrophil depleted), P. gingivalis, C. rectus, and A. actinomycetemcomitans were significantly more virulent. In contrast, while DEX treatment altered the characteristics of lesions caused by F. nucleatum, the extent of lesions produced by F. nucleatum and T. denticola was not substantially enhanced.

CONCLUSIONS

The results obtained from this study suggest that different microorganisms have the ability to provide individual pathologies which may act in an additive/synergistic fashion contributing to the tissue destruction noted in periodontitis.

Role of Ca2+ on endotoxin-sensitivity by galactosamine challenge: lipid peroxide formation and hepatotoxicity in zymosan-primed mice

This study was investigated to clarify the role of intracellular Ca2+ following endotoxin treatment (1 mg/kg, intraperitoneally) to D-galactosamine-sensitized mice (400 mg/kg, intraperitoneally), and to observe lipid peroxide levels, an index of hepatotoxicity, in endotoxin/galactosamine (Ga1N)-challenged mice under activation of macrophages, especially Kupffer cells, by zymosan. The liver lipid peroxide level and serum glutamic pyruvic transminase activity in mice 18 hr after administration of endotoxin/Ga1N were markedly higher than those in mice treated only with endotoxin. In spite of an increase in lipid peroxide formation, there was little or no effect of Ga1N administration on xanthine oxidase and superoxide dismutase activities in mice given endotoxin. However, the injection of verapamil (10 mg/kg, subcutaneously) markedly decreased lipid peroxide levels in liver of endotoxin/Ga1N-injected mice. In the mice given a Ca(2+)-deficient diet, lipid peroxide level in liver after endotoxin/Ga1N injection was markedly decreased compared to that in mice fed a normal diet. Administration of dexamethasone (200 micrograms/kg, intraperitoneally) in mice 1 hr before treatment with endotoxin/Ga1N did not induce lipid peroxide formation. Administration of endotoxin to Ga1N-treated mice resulted in a higher level of liver cytosolic free Ca2+ ([Ca2+]i) than that in endotoxin-treated mice. On the other hand, Ca(2+)-ATPase activity in liver plasma membrane in the endotoxin/Ga1N-treated mice was markedly decreased as compared with endotoxin alone. On the contrary, the Ca(2+)-ATPase activity in liver mitochondria was higher in endotoxaemic mice treated with GA1N than in mice given endotoxin alone.(ABSTRACT TRUNCATED AT 250 WORDS)

Therapeutic efficacy of a polymyxin B-dextran 70 conjugate in experimental model of endotoxemia

Numerous studies have suggested that lipopolysaccharide (LPS), a major component of the cell wall of gram-negative bacteria, is responsible for the initiation of gram-negative septic shock. Previously, others have designed therapeutic regimens to target the biologically active lipid A region of LPS by either neutralization of the biological properties of LPS or enhancement of clearance of this molecule. One such compound capable of neutralizing lipid A is the antibiotic polymyxin B. However, the clinical utility of polymyxin B is limited by its toxicity. We therefore covalently conjugated this antibiotic to the high-molecular-weight polysaccharide dextran 70, resulting in reduced toxicity of polymyxin B but retention of its endotoxin-neutralizing ability. The studies described in this report were designed to test the in vivo efficacy of this compound in an experimental animal model of gram-negative septic shock. Mice were administered graded doses of Escherichia coli or Pseudomonas aeruginosa along with D-galactosamine and the antibiotic imipenem. We had previously determined that antibiotic chemotherapy provides significant protection against E. coli-mediated lethality with smaller doses of bacteria; however, the antibiotic does not provide protection against larger doses of bacteria, but it is effective at killing the bacterial inoculum in vivo. Administration of the polymyxin B-dextran 70 conjugate provided significant protection when given with an antibiotic but was not effective by itself. A requirement for a pretreatment period prior to E. coli challenge was shown to depend upon the bacterial challenge dose. In other studies using this D-galactosamine sensitization model, we demonstrated that the lipid A-specific conjugate had no effect on lethality caused by staphylococcus aureus or tumor necrosis factor alpha. The results of these studies indicate that this compound is effective in preventing lethal gram-negative septic shock in mice and may be useful as a potential therapeutic agent in humans as well.

Tumor necrosis factor-induced hepatocyte apoptosis precedes liver failure in experimental murine shock models

We investigated the role of hepatocyte apoptosis in four different murine models of acute inflammatory liver failure. Liver damage induced in D-galactosamine-sensitized mice by endotoxin infection was initiated by processes typical of apoptosis, ie, chromatin condensation, DNA fragmentation, and formation of intracellular apoptotic bodies. DNA was cleaved into oligonucleosomal fragments in the liver before a significant rise of alanine aminotransferase in plasma occurred. Passive immunization against tumor necrosis factor (TNF) completely inhibited the injury caused by endotoxin. Direct injection of recombinant TNF-alpha also caused DNA fragmentation followed by alanine aminotransferase release into the plasma. Pretreatment of mice with interleukin-1 beta, which is known to suppress TNF-induced lethality, completely prevented apoptosis and liver failure in this model. These results demonstrate the causal role of TNF in endotoxin-induced hepatic apoptosis. TNF-inducible hepatocyte apoptosis in vivo was not only observed in D-galactosamine-sensitized mice, but also when the alternative transcriptional inhibitor actinomycin D was used. In mice injected with the TNF-inducing T cell mitogen concanavalin A, hepatic apoptosis was even noticed without requirement of additional sensitizers. We conclude that TNF-induced hepatocyte apoptosis is an early, general, and possibly causal event during experimental liver failure triggered by inflammatory stimuli.

Biological and serological characterization of Campylobacter jejuni lipopolysaccharides with deviating core and lipid A structures

Lipopolysaccharides from Campylobacter jejuni were tested for their ability to induce toxic lethality in galactosamine-sensitized mice, pyrogenicity in rabbits and tumour necrosis factor (TNF) secretion from mouse peritoneal macrophages. Compared with those of Salmonella LPS, lethal toxicity was 50% lower, pyrogenicity was 30- to 50-fold lower, and ability to induce TNF was 100-fold lower. C. jejuni LPS and lipid A exhibited higher phase-transition temperatures than those of Salmonella preparations, and thus the former have lower fluidity at 37 degrees C. This lower fluidity of acyl chains may influence the biological activities of C. jejuni LPS, but acyl chain characteristics and diaminoglucose replacing glucosamine in the hydrophilic lipid A backbone may also influence the supramolecular structure of lipid A, thereby affecting biological activities. Although diaminoglucose is present in the backbone of C. jejuni lipid A, antigenically the latter resembled classical lipid A of the Enterobacteriaceae when tested with anti-lipid A antibodies. Chemical investigations suggested the presence of glucuronic acid in an acid labile linkage in the inner core region, thus producing a structurally unusual region in C. jejuni LPS.

Human CAP18: a novel antimicrobial lipopolysaccharide-binding protein

CAP18 (18-kDa cationic antimicrobial protein) is a protein originally identified and purified from rabbit leukocytes on the basis of its capacity to bind and inhibit various activities of lipopolysaccharide (LPS). Here we report the cloning of human CAP18 and characterize the anti-LPS activity of the C-terminal fragment. Oligonucleotide probes designed from the rabbit CAP18 cDNA were used to identify human CAP18 from a bone marrow cDNA library. The cDNA encodes a protein composed of a 30-amino-acid signal peptide, a 103-amino-acid N-terminal domain of unknown function, and a C-terminal domain of 37 amino acids homologous to the LPS-binding antimicrobial domain of rabbit CAP18, designated CAP18(104-140). A human CAP18-specific antiserum was generated by using CAP18 expressed as a fusion protein with the maltose-binding protein. Western blots (immunoblots) with this antiserum showed specific expression of human CAP18 in granulocytes. Synthetic human CAP18(104-140) and a more active truncated fragment, CAP18(104-135), were shown to (i) bind to erythrocytes coated with diverse strains of LPS, (ii) inhibit LPS-induced release of nitric oxide from macrophages, (iii) inhibit LPS-induced generation of tissue factor, and (iv) protect mice from LPS lethality. CAP18(104-140) may have therapeutic utility for conditions associated with elevated concentrations of LPS.

TH1 cells trigger tumor necrosis factor alpha-mediated hypersensitivity to Pseudomonas aeruginosa after adoptive transfer into SCID mice

Recent experiments have shown that gamma interferon (IFN-gamma), either administered or induced in vivo, e.g., by certain bacteria, is a key mediator in inducing hypersensitivity to bacterial lipopolysaccharides. The source of endogenous IFN-gamma in this context (natural killer versus TH1 cells) has not been investigated yet. In order to investigate the role of antigen-specific, IFN-gamma-producing TH1 cells in murine Pseudomonas aeruginosa infection, a murine TH1 cell line was propagated in vitro by using recombinant P. aeruginosa outer membrane protein I. Adoptive transfer experiments were performed by intravenous injection of various amounts of TH1 cells into P. aeruginosa-challenged SCID mice. Adoptive transfer of 5 x 10(6) T cells into SCID mice followed by an intraperitoneal challenge with 1.4 x 10(6) CFU of live P. aeruginosa resulted in the rapid death of the animals within 12 h postchallenge, whereas transfer of lower T-cell doses and saline as a control did not cause any detrimental effects. After challenge with 2.8 x 10(6) CFU of P. aeruginosa, similar results were obtained 18 h postchallenge; however, at the end of the 72-h observation period, no significant differences in survival rates were obtained between the groups treated with different amounts of T cells. The rapid death of mice treated with 5 x 10(6) T cells was reflected by 860-fold-elevated levels of tumor necrosis factor alpha (TNF-alpha) present in serum 2 h postchallenge, whereas no significant differences in TNF-alpha serum levels were detectable in mice treated with lower doses of T cells or with saline. Pretreatment of T-cell-reconstituted SCID mice with neutralizing anti-IFN-gamma monoclonal antibodies completely protected mice from bacterial challenge and reduced TNF-alpha levels in serum. We conclude that under the experimental conditions described here, IFN-gamma- and interleukin-2-producing TH1 cells represent an important trigger mechanism inducing TNF-alpha-mediated hypersensitivity to bacterial endotoxin.

A mutation at histidine residue 135 of toxic shock syndrome toxin yields an immunogenic protein with minimal toxicity

Structure-function studies have revealed that the region between amino acids 115 and 141 of toxic shock syndrome toxin 1 (TSST-1) constitutes a biologically active domain. A critical residue appears to be histidine 135, since a site-directed mutation that alters the histidine to alanine (H135A) results in a loss of mitogenic activity and an absence of toxicity as measured in a rabbit infection model of toxic shock syndrome. We have characterized the mutant toxin further and report here on its immunogenic activity in rabbits and on the protective ability of mutant-specific antibodies in two animal models of toxin-mediated shock. Antibodies raised in rabbits by immunization with the purified H135A are fully cross-reactive with staphylococcal TSST-1 and wild-type recombinant TSST-1 (rTSST-1) expressed in Escherichia coli. The H135A antibodies neutralized the mitogenic activity for murine splenic T cells equally well as did TSST-1-specific polyclonal and monoclonal antibodies. In addition, the H135A antibodies blocked the production of tumor necrosis factor by spleen cells stimulated with rTSST-1. The toxicities of rTSST-1 and H135A were compared in D-galactosamine (D-GalNH2)-sensitized MRL-lpr/lpr mice. The nontoxicity of H135A was confirmed in this murine model of superantigen-induced septic shock. No toxicity of H135A was demonstrable at doses of 60 micrograms, while doses of rTSST-1 as low as 2 micrograms caused significant mortality within 24 to 72 h after challenge. Furthermore, subsequent to challenge of mice with H135A, no elevation in the serum levels of interleukin-2 or tumor necrosis factor was measurable. Passive immunization with H135A antibodies also protected MRL-lpr/lpr mice against lethal challenge with rTSST-1. Finally, rabbits actively immunized with purified H135A did not succumb to infection with a transformed strain of Staphylococcus aureus expressing rTSST-1. Additional animal studies will be required to confirm the immunizing potential of H135A and the efficacy of H135A antibodies as a neutralizing antitoxin.

Monoclonal antibodies specific for murine p55 and p75 tumor necrosis factor receptors: identification of a novel in vivo role for p75

Monoclonal antibodies (mAbs) specific for the murine p55 and p75 tumor necrosis factor (TNF) receptors were produced after immunization of Armenian hamsters with the purified soluble extracellular domains of each receptor protein. Four p55- (55R) and five p75 (TR75)-reactive mAbs immunoprecipitated the appropriate receptor from the surface of L929 cells. None of the mAbs cross-reacted with the other TNF receptor form. The mAbs were functionally characterized by their ability to inhibit ligand binding and influence TNF-dependent L cell cytolytic activity or proliferation of the murine cytolytic T cell clone CT6. One p55-specific mAb, 55R-593, displayed agonist activity, while two other p55-specific mAbs (55R-170 and -176) were found to be TNF antagonists. The fourth mAb (55R-286) had no functional effects on cells. Several antibodies specific for the p75 TNF receptor partially inhibited recombinant murine TNF-alpha-dependent cytolytic activity (60%). Blocking mAbs specific for p75 but not anti-p55 inhibited TNF-mediated proliferation of CT6 T cells. When used in vivo, p55- but not p75-specific mAbs protected mice from lethal endotoxin shock and blocked development of a protective response against Listeria monocytogenes infection. In contrast, both p55 and p75 mAbs individually blocked development of skin necrosis in mice treated with murine TNF-alpha. These data thus demonstrate the utility of the two families of murine TNF receptor-specific mAbs and identify a novel function of the p75 TNF receptor in vivo.

Antitumor necrosis factor antibodies reduce hepatic steatosis during total parenteral nutrition and bowel rest in the rat

BACKGROUND

In previous studies, we demonstrated the overgrowth of gram-negative bacteria in the gut and an enhanced release of tumor necrosis factor (TNF) by peritoneal macrophages, suggesting that endotoxin, TNF, or both, may act as hepatotoxins to produce hepatic steatosis during total parenteral nutrition (TPN) and bowel rest. The present study attempts to better define the role of each of these two mediators. The first part examines the LD50 for various doses of endotoxin in TPN-treated rats compared with free-feeding and free-feeding saline-infused rats. In the second part we repeatedly administered anti-TNF monoclonal antibodies to rats subjected to TPN and bowel rest.

METHODS

In the first set of experiments, 87 male Sabra rats were randomized into three groups: free-feeding, infused with normal saline, and infused with TPN. On day 7 of the experiment, all rats received an IV injection of endotoxin at various doses (1.5, 2.5, 5.0, 7.5, and 10 mg/kg). The LD50 in the three groups and at the various doses of lipopolysaccharide tested was determined at 24 hours postinjection. In the second set of experiments, 38 male Sabra rats were randomized into three groups: infused with normal saline and fed rat food ad libitum, infused with TPN, and infused with TPN but also receiving monoclonal antibodies against TNF.

RESULTS

Lower endotoxin doses were required to achieve LD50 in the two IV-infused groups (2.5 to 5.0 mg/kg) compared with the free-feeding group (7.5 mg/kg) (p < .03). These findings suggest a moderate increase in susceptibility to the lethal effect of endotoxin in IV-treated rats. The total hepatic fat and triglyceride levels, which were markedly increased in TPN rats, were significantly reduced by using anti-TNF antibodies. Enhanced TNF production by peritoneal macrophages during TPN was completely eliminated by anti-TNF antibodies, probably the result of suppressed TNF production.

CONCLUSIONS

The continuous translocation of endotoxin from gram-negative bacterial overgrowth in the gut during TPN and bowel rest results in enhanced release of TNF by macrophages. TNF causes hepatic dysfunction, portrayed in the present experimental model as hepatic steatosis. TPN-induced hepatic steatosis was significantly reduced by the administration of monoclonal antibodies against TNF-alpha.

Role of polymorphonuclear leukocytes in galactosamine hepatitis: mechanism of adherence to hepatic endothelial cells

To investigate the role of polymorphonuclear leukocytes in galactosamine-induced hepatic injury, we injected rats intraperitoneally with antiserum against rat polymorphonuclear leukocytes to deplete circulating neutrophils, then administered galactosamine plus lipopolysaccharide. Polymorphonuclear leukocytes in the hepatic sinusoids were increased after administration of galactosamine plus lipopolysaccharide, whereas pretreatment with the antiserum decreased the number of circulating leukocytes and reduced the mortality and the severity of hepatic injury. Serum collected 1 hr after galactosamine/lipopolysaccharide treatment enhanced in vitro polymorphonuclear leukocyte adherence to hepatic endothelial cells and induced leukocyte superoxide production. Intercellular adhesion molecule-1 expression on hepatic endothelial cells was also enhanced after stimulation with the serum. Polymorphonuclear leukocyte adhesion was partially inhibited by an antibody against tumor necrosis factor-alpha but not by superoxide dismutase. These results suggest that polymorphonuclear leukocytes play an important role in galactosamine-induced hepatic injury and that the accumulation and activation of leukocytes, as well as the enhanced expression of adhesion molecules on hepatic endothelial cells, can be induced by biologically active mediators such as tumor necrosis factor-alpha. In addition, prostaglandins E1 and E2 lessened the enhanced adherence of polymorphonuclear leukocytes and thus contributed to protection against hepatic injury.

Chronic biliary obstruction induces pulmonary intravascular phagocytosis and endotoxin sensitivity in rats

Endotoxin sensitivity varies among animal species and appears to correlate with the presence of pulmonary intravascular macrophage (PIM). In rats, which lack PIM, we investigated the hypothesis that chronic cholestatic liver injury leads to induction of PIM and endotoxin sensitivity. Rats were randomized to either common bile duct ligation (BDL) or sham-surgery and studied at 1 wk (acute cholestasis), 2 wk (cholestasis, early cirrhosis), and 4 wk (cholestasis, established cirrhosis) after surgery. Intravascularly injected fluorescent latex microspheres (1 micron diameter) were taken up by large phagocytic cells in lung parenchyma of BDL rats (at 2 and 4 wk), while no uptake was observed in lungs from control rats. Electronmicroscopy revealed accumulation of large, mononuclear, macrophage-like cells containing ingested latex particles within the pulmonary capillaries. Pulmonary intravascular phagocytosis, as reflected in lung uptake of 99mTc microaggregated albumin (Microlite, mean particle diameter = 1 micron), averaged 0.7 +/- 0.1% (mean +/- SEM) of total injected dose in 13 control rats and progressively increased with time after BDL (1 wk, 1.7 +/- 0.2%; 2 wk, 10.0 +/- 3.0%; 4 wk 35.1 +/- 5.9%). Rats with biliary cirrhosis were markedly sensitive to the lethal effects of low dose endotoxin and demonstrated marked lung edema at the time of death. Furthermore, the lung uptake of intravascular 125I-lipopolysaccharide was increased five-fold in cirrhotic rats. We conclude that chronic biliary obstruction leads to the induction of pulmonary intravascular phagocytes and enhances endotoxin sensitivity in rats. Pulmonary intravascular phagocytosis in patients with advanced cirrhosis may account for their increased susceptibility to sepsis-induced adult respiratory distress syndrome.

Construction of a BALB/c congenic mouse, C.C3H-Lpsd, that expresses the Lpsd allele: analysis of chromosome 4 markers surrounding the Lps gene

Development of a congenic BALB/c mouse strain that contains a segment of chromosome 4 including the Lpsd allele of the lipopolysaccharide (LPS)-hyporesponsive C3H/HeJ strain is presented. On the basis of LPS-induced spleen cell mitogenesis, macrophage tumor necrosis factor secretion, and tyrosine phosphorylation in vitro and lethality in galactosamine-sensitized mice in vivo, the C.C3H-Lpsd strain provides a model of LPS hyporesponsiveness that is comparable to that of the parental C3H/HeJ strain. Analysis of markers in this region indicates that length of the donor fragment is approximately 5.5 centimorgans. Thus, the C.C3H-Lpsd strain provides an important genetic tool for analysis of markers in this region and for examining functional effects of Lpsd expression on the BALB/c background.

Protection by alpha 1-acid glycoprotein against tumor necrosis factor-induced lethality

We here report that alpha 1-acid glycoprotein, a typical acute phase protein, protects mice from lethal shock induced by tumor necrosis factor (TNF) or endotoxin. The protection is observed both in normal and in galactosamine-sensitized mice. Optimal desensitization requires at least 3 mg alpha 1-acid glycoprotein administered 2 h before the lethal challenge. Under these conditions, complete inhibition of all TNF-induced metabolic changes was observed: fall in body temperature, release of liver transaminases, enhanced clotting time, and mortality. The known platelet aggregation-inhibitory activity of alpha 1-acid glycoprotein provides a possible explanation for this protective capacity.

Predominant role of the substituents on the hydroxyl groups of 3-hydroxy fatty acids of non-reducing glucosamine in lipid A for the endotoxic and antagonistic activity

The synthetic disaccharide precursor of lipid A (406: identical to lipid IVA) was found to reduce its endotoxic activity in mice by an order of 10(5) or more, by replacing the hydroxyl groups with succinyl or acetyl residues. Both the succinylated and acetylated 406 were also found to antagonize the endotoxic mitogenicity on murine splenocytes. Previous studies demonstrated that the succinylated or acetylated synthetic complete lipid A preparations retained the whole endotoxic activity [1994, Infect. Immunol. 62, 1705]. The drastic contrast in all of these results suggests the importance of the substituents on the hydroxyl groups of 3-hydroxy fatty acids of non-reducing glucosamine of lipid A for the activity and for transformation to the antagonistic structure.

An anti-idiotype antibody which mimics the inner-core region of lipopolysaccharide protects mice against a lethal challenge with endotoxin

Recently, we described the generation and characterization of an Armenian hamster Ab2 beta anti-idiotype monoclonal antibody (MAb4G2) specific for the binding site of a mouse monoclonal antibody, MAbY1-4A6, directed against the conserved 2-keto-3-deoxyoctulosonate (Kdo)-containing inner-core region of lipopolysaccharide (LPS) (S. K. Field, M. Pollack, and D. C. Morrison, Microb. Pathog. 15:103-120, 1993). In that study, mice and hamster immunized with MAb4G2 generated serum immunoglobulin G and M (IgG and IgM) antibodies which cross-react with Salmonella minnesota R595-chemotype rough mutant LPS (Re-LPS). In this report, we demonstrate that in C3Heb/FeJ mice, MAb4G2 elicits an immune response which is characterized by specific binding of antibody to Re-LPS, as assessed by enzyme-linked immunosorbent assay. The practical use of MAb4G2 as a potentially effective therapeutic agent against gram-negative bacterial sepsis is suggested by the demonstration that immunization of these mice with MAb4G2 results in significant protection of D-galactosamine-sensitized animals against an otherwise lethal dose of Re-LPS. Assessment of the temporal changes in Re-LPS-specific serum antibody titers from mice immunized with MAb4G2 or Re-LPS over a 40-day period indicates that immunization with Re-LPS elicits significantly higher titers of serum IgM antibodies compared with those in animals immunized with MAb4G2. Conversely, two immunizations with MAb4G2 result in an up to 10-fold increase in anti-Re-LPS-specific IgG serum antibody titers relative to those obtained in mice immunized with Re-LPS. Nineteen days after the secondary boost with MAb4G2, anti-Re-LPS-specific IgG serum antibody titers were significantly higher (three- to fourfold) compared with those in Re-LPS-treated animals. Initial immunization with the anti-idiotype antibody primes animals for enhanced secondary responses to Re-LPS, as assessed by the titers of anti-Re-LPS-specific IgG profiles. These data suggest the potential utility of MAb4G2 as a candidate vaccine against the lethal properties of gram-negative bacterial LPS.

Protection by sinomenine against endotoxin-induced fulminant hepatitis in galactosamine-sensitized mice

Sinomenine, an epimorphinan alkaloid, was tested for protecting hepatitis induced by lipopolysaccharide (LPS) in galactosamine (GalN)-sensitized mice. Sinomenine protected against the hepatic injuries in the dose range of 10-100 mg/kg in a dose-dependent manner and suppressed the production of tumor necrosis factor (TNF), which appeared in serum earlier than aminotransferases in GalN/LPS-treated mice. Sinomenine significantly suppressed the in vitro production of superoxide anion and hydrogen peroxide in the macrophage cultures stimulated with phorbol 12-myristate acetate. It is discussed that sinomenine prevents GalN/LPS-treated hepatic failure by suppressing TNF production and/or reactive oxygen generation.

Biological activities of lipopolysaccharide isolated from Vibrio cholerae O139, a new epidemic strain for recent cholera in Indian subcontinent

Biological activities of lipopolysaccharide (LPS) isolated from Vibrio cholerae O139, a new causative agent for recent cholera epidemic in Indian subcontinent, were investigated in comparison with those of LPS from O1 V. cholerae. V. cholerae O139 LPS exerted mitogenic activity, lethal toxicity and Shwartzman reaction to the same extent as those observed for O1 V. cholerae LPS, although these activities except for lethal toxicity were obviously lower than those of Salmonella typhimurium LT-2 LPS used as a reference. It was, therefore, suggested that O139 LPS does not contribute to the high infective and pathogenic potentials of the V. cholerae O139 strain as in the case of O1 V. cholerae.

Potentiation by granulocyte macrophage colony-stimulating factor of lipopolysaccharide toxicity in mice

GM-CSF is known to prime leukocytes for inflammatory stimuli in vitro. The objective of this study was to investigate the role of GM-CSF in vivo in a systemic inflammatory reaction syndrome. The results demonstrate a potentiation of LPS toxicity by GM-CSF in a mortality model as well as in a septic liver failure model in mice. Pretreatment of animals with 50 micrograms/kg GM-CSF induced lethality within 24 h in mice challenged with a subtoxic dose of LPS while controls survived > 72 h. A monoclonal anti-GM-CSF antibody significantly protected against a lethal LPS dose. Serum GM-CSF was inducible by LPS and peaked at 2 h. GM-CSF pretreatment dramatically potentiated systemic TNF release and hepatotoxicity induced by a subtoxic dose of LPS in galactosamine-sensitized mice. Potentiation of LPS hepatotoxicity was possible until 30 min after LPS challenge. Polyclonal anti-GM-CSF IgG protected against septic liver failure in this model and attenuated serum TNF concentrations. In vitro an ex vivo experiments revealed that after GM-CSF pretreatment LPS-induced IL-1 release from bone marrow or spleen cells was also enhanced. These findings suggest that GM-CSF represents an endogenous enhancer of LPS-induced organ injury, possibly by potentiating the release of proinflammatory cytokines such as TNF and IL-1.

Free hydroxyl groups are not required for endotoxic activity of lipid A

Previous studies demonstrated that lipid A from Salmonella abortusequi loses its B-cell mitogenicity for murine spleen cells as a result of the introduction of succinyl residues on hydroxyl groups and that the inactivated lipid A specifically antagonizes the mitogenicity of endotoxin. Hypothesizing that the hydroxyl groups are essential both for its biological activity and for producing nontoxic preparations having antagonistic activity, I tested the role of the hydroxyl groups in its activities by using well-characterized biologically active lipid A preparations synthesized chemically (Escherichia coli and Salmonella types 506 and 516, respectively) by the introduction of either succinyl or acetyl residues at the hydroxyl groups of each of these lipid A preparations. However, the biological activities of neither lipid A preparation were reduced at all after succinylation; in fact, succinylated 516 became much more potent than the original molecule with respect to most activities tested, i.e., lethal toxicity, Limulus gelation activity, and the induction of tumor necrosis factor release. On the other hand, when the hydroxyl groups were replaced with acetyl residues, the lethality and tumor necrosis factor-inducing activity of both lipid A preparations were decreased, whereas their Limulus gelation activity was increased. Mitogenicity was not affected much by the chemical modifications of either lipid A preparation. These findings indicate that although the residues introduced into the free hydroxyl groups of lipid A modulate its activities, the hydroxyl groups in lipid A need not exist in free form.

T cell activation-associated hepatic injury: mediation by tumor necrosis factors and protection by interleukin 6

This study investigates the molecular mechanisms underlying the induction of and protection from T cell activation-associated hepatic injury. When BALB/c mice were given a single intravenous injection of concanavalin A (Con A) (> or = 0.3 mg/mouse), they developed acute hepatic injury as assessed by a striking increase in plasma transaminase levels within 24 h. Histopathologically, only the liver was injured while moderate infiltration of T cells and polymorphonuclear cells occurred in the portal areas and around the central veins. The induction of hepatic injury was dependent on the existence as well as the activation of T cells, as untreated BALB/c nu/nu mice or BALB/c mice pretreated with a T cell-specific immunosuppressive drug, FK506, failed to develop disease. Significant increases in the levels of various cytokines in the plasma were detected before an increase in plasma transaminase levels. Within 1 h after Con A injection, tumor necrosis factor (TNF) levels peaked, this being followed by production of two other inflammatory cytokines, interleukin 6 (IL-6) and IL-1. Passive immunization with anti-TNF but not with anti-IL-1 or anti-IL-6 antibody, conferred significant levels of protection. Moreover, administration of rIL-6 before Con A injection resulted in an IL-6 dose-dependent protection. A single administration of a given dose of rIL-6 completely inhibited the release of transaminases, whereas the same regimen induced only 40-50% inhibition of TNF production. More than 80% inhibition of TNF production required four consecutive rIL-6 injections. These results indicate that: (a) TNFs are critical cytokines for inducing T cell activation-associated (Con A-induced) hepatitis; (b) the induction of hepatitis is almost completely controlled by rIL-6; and (c) rIL-6 exerts its protective effect through multiple mechanisms including the reduction of TNF production.

Multistep regulation mechanisms for tolerance induction to lipopolysaccharide lethality in the tumor-necrosis-factor-alpha-mediated pathway. Application of non-toxic monosaccharide lipid A analogues for elucidation of mechanisms

Lipid A is the active principle of lipopolysaccharide (LPS). Synthetic lipid A analogues with monosaccharide backbones, GLA-60, GLA-69 and GLA-58, which exhibit potent, weak and scarce agonistic activities of LPS, respectively, induced tolerance against LPS lethality in galactosamine-(GalN)-sensitized mice while none of them were pyrogenic in rabbits. The tolerance-inducing mechanisms were investigated focusing on the regulation of tumor-necrosis-factor-alpha(TNF-alpha)-mediated lethal pathway of LPS. Induction of serum TNF-alpha in LPS-challenged mice was suppressed by prior administration of these analogues as well as LPS. Prior treatment of murine macrophages with the substances suppressed LPS-stimulated TNF-alpha production in the culture supernatant and TNF-alpha mRNA expression in the cells as well. Lethal toxicity of TNF-alpha in GalN-sensitized mice was effectively suppressed by prior treatment with LPS, GLA-60 and GLA-69 but not by GLA-58. This protective effect was suggested to be mediated by endogenous TNF-alpha, which was induced by prior treatment with the effective substances, because either neutralization of endogenously induced TNF-alpha activity with an antibody or deletion of its induction by using LPS-resistant C3H/HeJ mice reduced the protective effect, and a detectable amount of TNF-alpha was produced by stimulating macrophages with the effective substances but not with GLA-58. These results indicated that multiple regulation steps (one is prior to and the others are following TNF-alpha production) are participating in the tolerance induction by LPS and some lipid A analogues and that GLA-58 is a characteristic compound which induces the tolerance by only blocking the step prior to TNF-alpha production.

Binding of lysozyme to lipopolysaccharide suppresses tumor necrosis factor production in vivo

Endotoxin (lipopolysaccharide [LPS]) released during gram-negative bacterial infection induces varieties of cytokines which directly and/or indirectly cause shock, disseminated intravascular coagulation, and death. We previously showed that lysozyme (LZM) was an LPS-binding protein and inhibited various immunomodulating activities of LPS. In this study, we examined the effect of LZM on the LPS-triggered septic shock model induced by carrageenan treatment and assessed by tumor necrosis factor production. The data presented in this report strongly suggest that LZM-LPS complex formation completely abrogates tumor necrosis factor production and the mortality caused by LPS and that LZM may be useful for the treatment of endotoxin shock.

Immunobiological properties of chemically defined lipid A from lipopolysaccharide of Porphyromonas (Bacteroides) gingivalis

Porphyromonas gingivalis 381 lipid A, characterized by beta-(1-6)-linked glucosamine disaccharide 1-phosphate, with one hydroxyacyl group and one acyloxyacl group, i.e., 3-hydroxy-15-methyl-hexadecanoyl and 3-hexadecanoyloxy-15-methylhexadecanoyl groups at the 2 and 2' positions, respectively, was less endotoxically active than the synthetic Escherichia-coli-type lipid A (compound 506), which possesses beta-(1-6)-linked glucosamine disaccharide 1,4'-bisphosphate, with two acyloxyacyl groups at the 2' and 3' positions and two 3-hydroxytetradecanoyl group at the 2 and 3 positions and the synthetic Salmonella-type lipid A (compound 516), which has three acyloxyacyl groups at the 2,2' and 3' positions and one hydroxyacyl group at the 3 position. P. gingivalis lipid A exhibited no or very low endotoxic activities, i.e., lethal toxicity in galactosamine-loaded mice, preparative ability for local Shwartzman reaction, pyrogenicity and Limulus test as compared with compounds 506 and 516. However, polyclonal B-cell activation of BALB/c mouse splenocytes was as strong as that of compound 506. Furthermore, P. gingivalis lipid A had stronger immunoadjuvant and hemagglutinating activities than compound 506. The absence of ester-linked phosphate at the 4' position and ester-linked fatty acids, and the presence and positions of fatty acids possessing considerable lengths of acyl chains are unique features of P. gingivalis lipid A, and they differentiate this lipid A from enterobacterial and other lipids A. The good balance between endotoxic properties and beneficial immunobiological activities of P. gingivalis lipid A may be attributable to these features.

New acyclic analogues of lipid A: synthesis of 4-phosphonoxybutyl and 3-phosphonoxypropyl glycosides of 2-amino-2-deoxy-D-glucose

Several analogues of lipid A have been synthesized, in which the reducing monosaccharide moiety of the parent molecule has been replaced by an acyclic spacer. The new compounds show high endotoxic activity and are able to protect neutropenic mice against pseudomonas infection, two properties characteristic of LPS-like molecules.

Similar cytokine but different coagulation responses to lipopolysaccharide injection in D-galactosamine-sensitized versus nonsensitized rats

To compare cytokine release and coagulation disturbances induced by administration of high versus low doses of endotoxin (lipopolysaccharide [LPS]), we used two endotoxin test systems similar in mortality but different in the degree of endotoxemia. One group of rats (n = 11) randomly received endotoxin (15.0 mg/kg of body weight intraperitoneally [i.p.]) and 1 ml of Ringer's solution (nonsensitized animals). The second group (n = 11) received 1 ml of D-galactosamine (500 mg/kg i.p.) and endotoxin (100 micrograms/kg i.p.) simultaneously (sensitized animals). Endotoxin levels in the plasma of nonsensitized rats were 1,000-fold higher than those in the plasma of sensitized rats (69.33 x 10(3) +/- 22.42 x 10(3) versus 75.8 +/- 27.08 ng of LPS per ml), leading to a mortality of 91% in nonsensitized rats versus 82% in the sensitized-rat model within 48 h postendotoxemia. Serum transaminase activity increased up to 100-fold in sensitized rats as a sign of hepatocyte damage. Despite the large difference in LPS levels in plasma, the time courses of the plasma tumor necrosis factor (TNF) increase were similar in the two groups, with a peak at 2 h (54 +/- 12 ng/ml in nonsensitized rats versus 43 +/- 12 ng/ml in sensitized rats), and also similar to that of a group of nonsensitized rats (n = 5) that received a low dose of LPS (100 micrograms/kg) only (52 +/- 21 ng/ml), while D-galactosamine alone did not induce TNF release. Despite similar TNF levels, a more pronounced coagulation disorder was observed at 4 h in nonsensitized rats (with the high LPS dose) as measured by platelet counts, plasma fibrinogen levels, and activated partial thromboplastin time prolongation (191 x 10(3) +/- 107 x 10(3) cells per microliter, 40 +/- 24 mg/dl, and 53 +/- 15 s, respectively) than in rats with the low LPS dose either sensitized (495 x 10(3) +/- 153 x 10(3), 95 +/- 49, and 38 +/- 16, respectively) or nonsensitized (439 x 10(3) +/- 62 x 10(3), 170 +/- 18, and 35 +/- 11, respectively).(ABSTRACT TRUNCATED AT 400 WORDS)

Differential antibiotic-induced release of endotoxin from gram-negative bacteria

Treatment of log phase cultures of Escherichia coli with cell wall active antibiotics results in increased exposure of immunologically reactive lipid A epitopes of lipopolysaccharide (LPS) and release of soluble LPS into culture supernatants. Comparison of the efficacy of two cell wall active antibiotics, ceftazidime, a penicillin-binding protein 3 selective antibiotic, and imipenem, a penicillin-binding protein 2 selective antibiotic, for their relative efficacy in mediating LPS release indicated quantitative but not qualitative differences, with the former antibiotic manifesting a significantly broader range of concentrations at which LPS release could be demonstrated. Comparison of the relative efficacy of these two antibiotics in a mouse bacteraemia model in which animals were made hypersensitive to the lethal effects of endotoxin by treatment with D-galactosamine indicated that the latter antibiotic may provide a greater level of protection. These studies suggest that the release of endotoxin mediated by antibiotic treatment may contribute to the pathogenesis of disease in infectious due to gram-negative organisms.

Role of acute-phase proteins in interleukin-1-induced nonspecific resistance to bacterial infections in mice

Treatment with a single low dose (80 to 800 ng) of interleukin-1 (IL-1) 24 h before a lethal bacterial challenge of granulocytopenic and normal mice enhances nonspecific resistance. Since IL-1 induces secretion of acute-phase proteins, liver proteins which possess several detoxifying effects, we investigated the role of these proteins in the IL-1-induced protection. Inhibition of liver protein synthesis with D-galactosamine (GALN) completely inhibited the IL-1-induced synthesis of acute-phase proteins. GALN pretreatment abolished the protective effect of IL-1 on survival completely (neutropenic mice infected with Pseudomonas aeruginosa) or partially (nonneutropenic mice infected with Klebsiella pneumoniae). Pretreatment with IL-6, a cytokine induced by IL-1, did not reproduce the protection offered after IL-1 pretreatment, nor did it enhance or deteriorate the IL-1-enhanced resistance to infection. A protective effect of IL-1 via effects on glucose homeostasis during the acute-phase response was investigated by comparing plasma glucose levels in IL-1-treated mice and control mice before and during infection. Although glucose levels in IL-1-pretreated mice were somewhat higher in the later stages of infection, no significant differences from levels in control mice were present, and the glucose levels in control-treated animals never fell to hypoglycemic values. We conclude that the IL-1-induced nonspecific resistance is mediated neither by the induction of IL-6 nor by the effects of IL-1 on glucose homeostasis. Acute-phase proteins generated after IL-1 pretreatment, however, seem to play a critical role in the IL-1-induced protection to infection.

Role of the physical state of Salmonella lipopolysaccharide in expression of biological and endotoxic properties

Lipopolysaccharide (LPS) extracted from three strains of Salmonella typhimurium, i.e., the rough Re mutant SL1102, the rough Ra mutant TV119, and the smooth strain SH4809, was first electrodialyzed (eLPS) and then divalent cation deprived by EDTA treatment and finally made monomeric by deoxycholate solubilization. The removal of excess detergent by extensive dialysis in the absence of mineral cations resulted in the reassociation of LPS subunits into monodisperse micelles of reduced aggregation number (dLPS) as estimated by electron microscopy and gel filtration chromatography. For all LPS chemotypes tested, the developed procedure reproducibly results in stable and clear solutions of dLPS in concentrations of up to 100 mg/ml. The dLPS and eLPS preparations possessed the same reactivity with monoclonal antibodies (MAbs) raised against different LPS domains. The 100% lethal dose in galactosamine-sensitized mice of 0.01 microgram for the smooth eLPS was from 10- to 100-fold lower than that of dLPS at 0.1 to 1.0 microgram. dLPS from both the smooth strain and the Ra mutant had a significantly reduced capacity to activate the proenzyme cascade in the Limulus amoebocyte lysate assay in comparison with the slightly reduced activity of dLPS from the Re mutant. In contrast, dLPS as well as the deoxycholate-dispersed and then diluted eLPS from the smooth strain had a higher mitogenic activity on splenocytes than eLPS. The results indicate that the biological and endotoxic properties of LPS are significantly influenced by the physical state of its aggregates in aqueous solutions. The approach developed for production of a stable and dispersed form of LPS should further assist in investigation of LPS properties and interpretation of the data of endotoxic research.

Lipopolysaccharide-binding protein as a major plasma protein responsible for endotoxemic shock

Because lipopolysaccharide (LPS)-binding protein (LBP) sensitizes monocytes to LPS in vitro, it has been suggested that LBP initiates host defenses against Gram-negative bacteria. The role of LBP in vivo, and particularly in endotoxemic shock, is unknown, however. Therefore an IgG against murine LBP was prepared. It was found to neutralize binding of LPS and subsequent activation of murine macrophages in vitro. This anti-LBP protected mice against the lethal effect of LPS when given at the same time as LPS challenge, but it failed to protect mice when delayed 15 min after LPS challenge. The same preparation was also effective after challenge with lipid A but not after challenge with Staphylococcus aureus enterotoxin. The protection was correlated with a strong decrease of circulating tumor necrosis factor. These data demonstrate that in vivo LBP is a major mediator of the lethal effects of endotoxemia.

Superantigen mediated shock: a cytokine release syndrome

Treatment of animals with superantigens results in profound immunological changes. A major fraction of all peripheral T cells becomes activated in vivo. Subsequently, successive waves of cytokines are produced with TNF playing a central pathophysiologic role. In addition, if the liver is damaged by an as yet poor defined mechanism the consequences of the cytokine syndrome are life threatening. However, TNF alone is not sufficient to cause death, instead synergizing interactions with cytokines like IL-1, IL-6, and IFN-gamma are probably involved. On the other hand, certain experimental conditions prevent these waves of cytokines and consequently lethal shock. Furthermore, a significant fraction of SA reactive T cells are deleted by programmed cell death 10 to 24 hours after treatment. Thereafter the surviving cells proliferate vigorously until day 2 or 3, followed by a second wave of apoptosis resulting in reduced SA reactive T cell numbers as compared to pretreatment levels. Of course, many aspects of the complicated events are only marginally understood and deserve further investigation.

Antiinflammatory properties of hepatic acute phase proteins: preferential induction of interleukin 1 (IL-1) receptor antagonist over IL-1 beta synthesis by human peripheral blood mononuclear cells

This study was undertaken to determine whether acute phase proteins (APP) induce the synthesis of interleukin 1 beta (IL-1 beta) and its specific antagonist, IL-1 receptor antagonist (IL-1Ra), in human peripheral blood mononuclear cells (PBMC). PBMC from healthy volunteers were incubated with C-reactive protein (CRP), alpha 1-antitrypsin (alpha 1-AT), or alpha 1-acid glycoprotein (AGP), and the levels of IL-1 beta and IL-1Ra produced were measured by specific radioimmunoassay. To evaluate the effects of alpha 1-AT further, a synthetic pentapeptide FVYLI corresponding to the minimal binding sequence for the serpine-enzyme complex receptor was also evaluated. PBMC incubated for 24 h with CRP, alpha 1-AT, or the pentapeptide FVYLI synthesized large quantities of IL-1Ra, 5-10-fold greater than the amount of IL-1 beta produced by these cells. AGP induced significantly less IL-1Ra than the other APP tested. These effects were shown to be specific, in that polyclonal antibodies against CRP, alpha 1-AT, and AGP eliminated the cytokine production induced by these respective proteins. CRP, alpha 1-AT, FVYLI, and AGP were synergistic with low concentrations of endotoxin in the induction of both IL-1Ra and IL-1 beta synthesis. We suggest that the preferential induction of IL-1Ra by APP may contribute to their antiinflammatory effects and provide an important regulatory signal for the acute phase response.

Interleukin 10 protects mice against staphylococcal enterotoxin B-induced lethal shock

We investigated the ability of interleukin 10 (IL-10) to protect mice against lethal shock induced by staphylococcal enterotoxin B (SEB). Treatment of mice with IL-10 prevented the death of mice injected with SEB in a dose-dependent manner. IL-10-mediated protection was apparent when administered either prior to or concurrent with SEB but was less effective when administered following SEB injection. This observation indicates that IL-10 is capable of regulating T-cell activation in vivo.

A broadly cross-protective monoclonal antibody binding to Escherichia coli and Salmonella lipopolysaccharides

During the last decade, episodes of sepsis have increased and Escherichia coli has remained the most frequent clinical isolate. Lipopolysaccharides (LPS; endotoxin) are the major toxic and antigenic components of gram-negative bacteria and qualify as targets for therapeutic interventions. Molecules that neutralize the toxic effects of LPS are actively investigated. In this paper, we describe a murine monoclonal antibody (MAb; WN1 222-5), broadly cross-reactive and cross-protective for smooth (S)-form and rough (R)-form LPS. As shown in enzyme-linked immunosorbent assay and the passive hemolysis assay, WN1 222-5 binds to the five known E. coli core chemotypes, to Salmonella core, and to S-form LPS having these core structures. In immunoblots, it is shown to react with both the nonsubstituted core LPS and with LPS carrying O-side chains, indicating the exposure of the epitope in both S-form and R-form LPS. This MAb of the immunoglobulin G2a class is not lipid A reactive but binds to E. coli J5, an RcP+ mutant which carries an inner core structure common to many members of the family Enterobacteriaceae. Phosphate groups present in the inner core contribute to the epitope but are not essential for the binding of WN1 222-5 to complete core LPS. Cross-reactivity for clinical bacterial isolates is broad. WN1 222-5 binds to all E. coli clinical isolates tested so far (79 blood isolates, 80 urinary isolates, and 21 fecal isolates) and to some Citrobacter, Enterobacter, and Klebsiella isolates. This pattern of reactivity indicates that its binding epitope is widespread among members of the Enterobacteriaceae. WN1 222-5 exhibits biologically relevant activities. In vitro, it inhibits the Limulus amoebocyte lysate assay activity of S-form and R-form LPS in a dose-dependent manner and it neutralizes the LPS-induced release of clinically relevant monokines (interleukin 6 and tumor necrosis factor). In vivo, WN1 222-5 blocks endotoxin-induced pyrogenicity in rabbits and lethality in galactosamine-sensitized mice. The discovery of WN1 222-5 settles the long-lasting controversy over the existence of anti-core LPS MAbs with both cross-reactive and cross-protective activity, opening new possibilities for the immunotherapy of sepsis caused by gram-negative bacteria.

Mice lacking the tumour necrosis factor receptor 1 are resistant to TNF-mediated toxicity but highly susceptible to infection by Listeria monocytogenes

Tumour necrosis factor (TNF), jointly referring to TNF alpha and TNF beta, is a central mediator of immune and inflammatory responses; its activities are mediated by two distinct receptors, TNFR1 (p55) and TNFR2 (p75) (reviewed in refs 1-3). The cytoplasmic domains of the TNFRs are unrelated, suggesting that they link to different intracellular signalling pathways. Although most TNF responses have been assigned to one or the other of the TNF receptors (mostly TNFR1), there is no generally accepted model for the physiological role of the two receptor types. To investigate the role of TNFR1 in beneficial and detrimental activities of TNF, we generated TNFR1-deficient mice by gene targeting. We report here that mice homozygous for a disrupted Tnfr1 allele (Tnfr1(0)) are resistant to the lethal effect of low doses of lipopolysaccharide after sensitization with D-galactosamine, but remain sensitive to high doses of lipopolysaccharide. The increased susceptibility of Tnfr1(0)/Tnfr1(0) mutant mice to infection with the facultative intracellular bacterium Listeria monocytogenes indicates an essential role of TNF in nonspecific immunity.

An interleukin-6-induced acute-phase response does not confer protection against lipopolysaccharide lethality

Lipopolysaccharide (LPS), a component of gram-negative bacterial outer cell walls, can stimulate lymphoreticular cells to produce cytokines such as tumor necrosis factor alpha (TNF-alpha), interleukin-1 (IL-1), and IL-6. One of these proinflammatory cytokines, IL-6, induces hepatic synthesis of a class of proteins termed acute-phase proteins. D-Galactosamine inhibits acute-phase protein synthesis and concurrently sensitizes mice to a lethal dose of LPS approximately 10,000-fold. From these observations, we hypothesized that the acute-phase response may serve as a defense mechanism for protection of the host against the deleterious effects of LPS. To test this hypothesis, murine recombinant IL-6 (mrIL-6) was used to induce an acute-phase response prior to a lethal LPS challenge in both D-galactosamine-treated and normal mice. Induction of the acute-phase response by mrIL-6 was quantitated by measuring the concentrations of fibrinogen and complement component C3, two well-characterized acute-phase proteins, in the circulation. The effect of acute-phase and normal serum on TNF-alpha release by peritoneal macrophages stimulated with LPS in vitro was also examined. The results of these studies confirmed the induction of the acute-phase response by mrIL-6, as reflected in an approximate doubling in circulating levels of fibrinogen and C3. However, when either D-galactosamine-sensitized or normal mice were challenged with a lethal dose of LPS at various times after mrIL-6 administration, the acute-phase response induced by mrIL-6 did not alter either cumulative lethality or the kinetics of lethality. Additionally, compared with normal serum, acute-phase serum did not affect TNF-alpha release by peritoneal macrophages following LPS-mediated stimulation in vitro. Collectively, these studies would not support a dominant role for an IL-6-mediated acute-phase response as contributing to the resistance of normal mice compared with D-galactosamine-sensitized mice in LPS-induced lethal toxicity.

Induction of early gene expression in murine macrophages by synthetic lipid A analogs with differing endotoxic potentials

Numerous lipid A analogs have been synthesized in an attempt to dissociate endotoxic activities from beneficial immunomodulatory activities. In the present study, we have evaluated select lipid A analogs in macrophages for their ability to induce a panel of lipopolysaccharide (LPS)-inducible genes to gain insights into the molecular mechanisms which underlie endotoxicity. We evaluated three monosaccharide lipid A analogs: SDZ MRL 953, an agonist with an improved therapeutic margin over endotoxin; SDZ 281.288, a more toxic analog; and SDZ 880.431, an analog with proven LPS-inhibitory activity. In addition, three disaccharide lipid A analogs (i.e., lipid IVA, SDZ 880.611, and SDZ 880.924) that differ in acylation and phosphorylation patterns were also examined and compared with synthetic lipid A. With the exception of SDZ 880.431, each of these structurally diverse analogs was able to induce the complete panel of LPS-inducible genes, specifically genes which encode tumor necrosis factor alpha (TNF-alpha), interleukin-1 beta, 75-kDa type 2 TNF receptor (D7), IP-10, D3, and D8. These results underscore that macrophage stimulation by lipid A analogs is permissive to considerable structural diversity. Structures with favorable therapeutic indices (SDZ MRL 953, SDZ 880.611, and SDZ 880.924) were not different from structures with poor therapeutic indices (lipid A, lipid IVA, and SDZ 281.288) with regard to gene induction. Nonetheless, the nontoxic SDZ MRL 953 was approximately 1,000-fold less potent than synthetic lipid A at inducing TNF-alpha secretion, and perhaps this contributes to the lack of toxicity exhibited by this compound. The ability of compound SDZ 880.431 to inhibit TNF-alpha secretion induced by both SDZ MRL 953 and smooth LPS suggests that the monosaccharide and smooth LPS share a receptor or a portion thereof. A pattern of protein tyrosine phosphorylation similar to that induced by LPS was stimulated by the monosaccharide SDZ MRL 953 and SDZ 281.288 and disaccharides lipid IVA, SDZ 880.924, and SDZ 880.611, providing evidence for a common signalling pathway.

Protective role of interleukin 6 in the lipopolysaccharide-galactosamine septic shock model

C57BL/6J mice given low doses of lipopolysaccharide (LPS) (100 ng per mouse) plus D-galactosamine (8 mg per mouse) die within 24 h following LPS administration. We used this septic shock model to confirm the role of tumor necrosis factor in mortality using a monoclonal antibody to tumor necrosis factor to prevent lethality. Furthermore, we demonstrated that interleukin 6, rather than playing a lethal role, protected mice against death in this septic shock model. Antibody to interleukin 6 did not affect the fatal outcome in this low-LPS-dose model. However, pretreatment with antibody to tumor necrosis factor did protect the mice against death, in a dose-dependent manner. Moreover, mortality was enhanced by pretreatment with antibody to interleukin 6 when tumor necrosis factor was partly limited by anti-tumor necrosis factor treatment. Mortality was significantly reduced by pretreatment with both recombinant interleukin 6 and low doses of antibody to tumor necrosis factor; in the absence of the low dose of antibody to tumor necrosis factor, interleukin 6 alone did not confer any protection. These data demonstrate in vivo antagonistic activities of tumor necrosis factor and interleukin 6 and show that interleukin 6 can play a protective role against death from septic shock.

Mechanisms and mediators in hepatic necrosis

Necrotic processes may be restricted to individual cell types of the liver or afflict several liver cells sequentially. Noxious agents may induce necrobiosis by different mechanisms of injury. In many instances, however, similar or identical terminal processes are involved, e.g. accumulation of Ca2+ in cytosol or mitochondria, termination of nucleic acid and protein syntheses or membrane damage. Apoptosis may also be a relevant feature of hepatic necrosis. Inhibition of mRNA synthesis and post-translational glycosylations of proteins of the hepatocytes is instrumental in D-galactosamine-induced hepatocellular necrosis. An early event seen after administration of D-galactosamine plus endotoxin is an accumulation of neutrophilic granulocytes in the liver sinusoids. It results from the tumor necrosis factor (TNF)-alpha-induced adhesion of polymorphonuclear leukocytes to the sinusoidal endothelium and the vasoconstriction due to thromboxane A2 that is secreted by activated Kupffer cells. Temporal hypoxia and nutrient deprivation as well as the activation of the granulocytes with release of reactive oxygen species and proteinases appear to be severe consequences. Hypoxia followed by reperfusion (reoxygenation) must be considered as a mechanism of liver cell necrosis producing reactive oxygen species; oxygen radicals were reported to be signals for the activation of nuclear factor kappa B and thereby for the cytotoxicity of cytokines.

Endogenous and exogenous glucocorticoids have different roles in modulating endotoxin lethality in D-galactosamine-sensitized mice

Endotoxin sensitivity and dexamethasone protection have been assessed in mice that were adrenalectomized and also treated with D-galactosamine at the time of endotoxin challenge. Our data establish that adrenalectomy did not detectably alter the magnitude of the increased sensitivity induced by D-galactosamine alone. Furthermore, protection provided by acute exogenous glucocorticoid treatment was still demonstrable in these mice and was not influenced by chronic experimentally induced glucocorticoid deficiency. Our data confirm that the adrenalectomized mouse model of endotoxin lethality is characterized by increased sensitivity to endotoxin and establish that the magnitude of this sensitizing effect is more than 100-fold. We also show for the first time that adrenalectomy causes an appreciable kinetic shift in the endotoxic crisis and that dexamethasone, given at the time of endotoxin challenge, will significantly reverse the increased sensitivity to lethality. Our results indicate that the protective effects of corticosteroids may involve important chronic as well as acute responses. In particular, we conclude that endogenous glucocorticoid need not always increase host resistance to endotoxin, nor does such a circumstance eliminate the possibility for exogenous glucocorticoid-mediated protective effects.

An antagonist of platelet-activating factor suppresses endotoxin-induced tumor necrosis factor and mortality in mice pretreated with carrageenan

We found that carrageenan (CAR), that is, sulfated polygalactose, can enhance both lipopolysaccharide (LPS)-induced tumor necrosis factor (TNF) production and the rate of lethality in mice (M. Ogata, S. Yoshida, M. Kamochi, A. Shigematsu, and Y. Mizuguchi, Infect. Immun. 59:679-683, 1991). It has been reported that platelet-activating factor (PAF) antagonists reduce the rate of mortality from endotoxin shock. However, there are few reports regarding the effect of PAF antagonists on TNF production. The aim of the present study is to examine the effect of TCV-309, a new PAF antagonist, on LPS-induced TNF production and mortality in mice pretreated with CAR. ddY mice (6 to 7 weeks old) were injected intraperitoneally with CAR (5 mg per mouse) and were then divided into two groups: mice treated with a PAF antagonist (TCV-309; Takeda Pharmaceutical Co.) and control mice. The mice treated with PAF antagonist received indicated doses of TCV-309 subcutaneously (s.c.) at 30 min before LPS injection, while the control mice received 1 ml of saline s.c. at the same time. All mice were stimulated by intravenous injection of LPS (50 micrograms per mouse) at 24 h after pretreatment with CAR. At intervals after injection of LPS, serum samples were obtained for a TNF assay in which cytotoxicity to L929 cells was measured. TCV-309 both significantly suppressed LPS-induced TNF production and reduced mortality in a dose-dependent manner. When TCV-309 was administered at 30 min before injection of LPS, the effect of TCV-309 on the suppression of TNF activity was at its peak. Treatment with TCV-309 (990 micrograms per mouse) s.c. significantly improved the survival rate after challenge with LPS compared with the survival rate of control mice. Although the 50% lethal dose of LPS was 15 micrograms per mouse for control mice, it increased to 102 micrograms per mouse for mice that were treated s.c. with TCV-309 (990 micrograms per mouse). Even in vitro, TCV-309 also inhibited LPS-induced TNF production in thioglycolate-elicited macrophages. It was concluded that PAF plays an important role in endotoxin-induced TNF production and mortality.

Cycloheximide or nordihydroguaiaretic acid protects mice against the lethal and hepatocytolytic effects of a combined challenge with D-galactosamine and bacterial endotoxin

Both cycloheximide and nordihydroguaiaretic acid protect mice against the fatalities and associated panlobular hepatocyte necrosis that follow a challenge with D-galactosamine and bacterial endotoxin. It is proposed that cycloheximide acts as an inhibitor of the endotoxin-induced activation of phospholipase A2, thereby inhibiting the synthesis of leukotrienes which is now known to be a prerequisite for tumour necrosis factor-alpha (TNF) biosynthesis, the latter cytokine being regarded as the terminal mediator of the fatal D-galactosamine and endotoxin-induced syndrome. Nordihydroguaiaretic acid protection is explained by its inhibition of lipoxygenase enzymes, and thus ultimately of TNF production in response to endotoxin.