Macrophage activation in response to S-form lipopolysaccharides (LPS) separated by centrifugal partition chromatography from wild-type LPS: effects of the O-polysaccharide portion of LPS

Separation of wild-type lipopolysaccharides by centrifugal partition chromatography: isolation of smooth form species

The smooth (S)-form lipopolysaccharides (LPSs) having long O-polysaccharides were successfully isolated by centrifugal partition chromatography from the co-existing rough (R)-form species from the LPSs of wild-type strains of Salmonella enterica, serovars abortus equi and friedenau, and from Citrobacter freundii. Separation is based on different partition behaviors of the R- and S- form LPS species between aqueous and organic phases. The procedure described proved to be convenient, reproducible and readily applicable to large amounts of various LPS. It is another tool to study the relationship between chemical structure and biological activity of LPS.

Intact rough- and smooth-form lipopolysaccharides from Escherichia coli separated by preparative gel electrophoresis exhibit differential biologic activity in human macrophages

We established a new preparative separation procedure, based on DOC/PAGE, to isolate intact lipopolysaccharide (LPS) fractions from natural LPS preparations of Escherichia coli. Analysis of the chemical integrity of LPS fractions by MS showed that no significant chemical modifications were introduced by the procedure. Contamination with toll-like receptor 2 (TLR2)-reactive cell-wall components present in the natural LPS mixture was effectively removed by the procedure, as determined by the absence of reactivity of the purified fractions in a HEK293-TLR2 cell line. Biologic analysis of LPS fractions derived from E. coli O111 in human macrophages demonstrated that the rough (R), semirough (SR) and smooth (S) LPS fractions were highly active at inducing tumor necrosis factor-alpha (TNF-α) in the presence of human serum; however, on a weight basis the R-LPS and SR-LPS fractions were more active, by a factor of 10-100, than was the S-LPS fraction. Under serum-free conditions, the natural LPS mixture, as well as the R-LPS and SR-LPS fractions, showed dose-dependent activation of macrophages, although the response was attenuated by about 10- to 100-fold. In contrast, the S-LPS fraction failed to induce TNF-α. Remarkably, the dose-response of the natural LPS mixture resembled that of the R-LPS and SR-LPS fractions, supporting that short-chain (R and SR) forms of LPS dominate the innate immune response of human macrophages to LPS in vitro. Biologic activity to the S-LPS fraction under serum-free conditions could be restored by the addition of recombinant lipopolysaccharide-binding protein (LBP). In contrast, soluble cluster of differentiation antigen 14 was not able to confer activity of the S-LPS fraction, indicating a crucial role of LBP in the recognition of S-LPS by human macrophages.

Innate immune responses of primary murine macrophage-lineage cells and RAW 264.7 cells to ligands of Toll-like receptors 2, 3, and 4

Although studies have been performed to characterize responses of macrophages from individual anatomical sites (e.g., alveolar macrophages) or of murine-derived macrophage cell lines to microbial ligands, few studies compare these cell types in terms of phenotype and function. We directly compared the expression of cell surface markers and functional responses of primary cultures of three commonly used cells of monocyte-macrophage lineage (splenic macrophages, bone marrow-derived macrophages, and bone marrow-derived dendritic cells) with those of the murine-leukemic monocyte-macrophage cell line, RAW 264.7. We hypothesized that RAW 264.7 cells and primary bone marrow-derived macrophages would be similar in phenotype and would respond similarly to microbial ligands that bind to either Toll-like receptors 2, 3, and 4. Results indicate that RAW 264.7 cells most closely mimic bone marrow-derived macrophages in terms of cell surface receptors and response to microbial ligands that initiate cellular activation via Toll-like receptors 3 and 4. However, caution must be applied when extrapolating findings obtained with RAW 264.7 cells to those of other primary macrophage-lineage cells, primarily because phenotype and function of the former cells may change with continuous culture.

Biological properties of the native and synthetic lipid A of Porphyromonas gingivalis lipopolysaccharide

INTRODUCTION AND METHODS

A pentaacyl and diphosphoryl lipid A molecule found in the lipid A isolated from Porphyromonas gingivalis lipopolysaccharide (LPS) was chemically synthesized, and its characteristics were evaluated to reconfirm its interesting bioactivities including low endotoxicity and activity against LPS-unresponsive C3H/HeJ mouse cells.

RESULTS

The synthesized P. gingivalis lipid A (synthetic Pg-LA) exhibited strong activities almost equivalent to those of Escherichia coli-type synthetic lipid A (compound 506) in all assays on LPS-responsive mice, and cells. LPS and native lipid A of P. gingivalis displayed overall endotoxic activities, but its potency was reduced in comparison to the synthetic analogs. In the assays using C3H/HeJ mouse cells, the LPS and native lipid A significantly stimulated splenocytes to cause mitosis, and peritoneal macrophages to induce tumor necrosis factor-alpha and interleukin-6 production. However, synthetic Pg-LA and compound 506 showed no activity on the LPS-unresponsive cells. Inhibition assays using some inhibitors including anti-human Toll-like receptor 2 (TLR2) and TLR4/MD-2 complex monoclonal antibodies showed that the biological activity of synthetic Pg-LA was mediated only through the TLR4 signaling pathway, which might act as a receptor for LPS, whereas TLR2, possibly together with CD14, was associated with the signaling cascade for LPS and native lipid A of P. gingivalis, in addition to the TLR4 pathway.

CONCLUSION

These results suggested that the moderated and reduced biological activity of P. gingivalis LPS and native lipid A, including their activity on C3H/HeJ mouse cells via the TLR2-mediated pathway, may be mediated by bioactive contaminants or low acylated molecules present in the native preparations having multiple lipid A moieties.

Synthesis, purification and surface activities of the human pulmonary surfactant protein-C (SP-C) analogue, SP-CL16 (6-28)

We previously reported that a human analogue of pulmonary surfactant protein-C (SP-C), SP-CL16 (6-28), with 23 residues (Fig. 1) was the most active analogue in a reconstituted lipid mixture and had the shortest chain among the poly-leucine-analogues examined. In the present study, we examined a new method of preparing this analogue, that is, stepwise solid-phase synthesis employing the Fmoc method followed by centrifugal partition chromatography (CPC) using an n-hexane/CH3OH/H2O/trifluoroacetic acid (TFA) (1000: 1000:1:2, v/v) solvent system according to the descending method. The synthetic peptides were identified by matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectrometry in search of activity to improve the in vitro surface activity of a ternary lipid mixture composed of dipalmitoylphosphatidylcholine, egg-phosphatidylglycerol and palmitic acid (75:25:10, w/w) in a Langmuir-Wilhelmy surface balance. SP-CL16 (6-28) seemed comparable in surface activity with Surfacten (Surfactant-TA), a modified surfactant preparation which has been used for the treatment of respiratory distress syndrome.

High-efficiency passive elution of bacterial lipopolysaccharides from polyacrylamide gels

We recently described a method for recovering polyacrylamide-gel-separated bacterial lipopolysaccharides (LPS) based on the sensitive on-gel LPS detection (1-10 ng/band) with zinc-imidazole followed by passive elution from 32 microm average size gel microparticles into water. With this procedure, the recovery of rough- or semismooth-type LPS after 3 h elution is about 70-80%, while that of smooth LPS is only about 10%. Here we evaluated whether a simple replacement of water with other eluents would enhance the passive diffusion of LPS. We found that solutions of the detergents sodium dodecyl sulfate (SDS), sodium deoxycholate (DOC) and Triton X-100, or mixtures of the organic solvents acetonitrile and triethylamine and water, increased the recovery of a smooth LPS band from Vibrio cholerae O1 in a concentration-dependent manner. Furthermore, a quantitative recovery of rough or smooth LPS from V. cholerae O1, Escherichia coli O111:B4, E. coli K-235, or Serratia marcescens was feasible in 1% SDS or DOC after 3 h or in 5% triethylamine after only 2 min. A simple dilution of SDS or DOC or evaporation of triethylamine rendered the eluted LPS preparations compatible with biochemical activity determination, as tested by Limulus amebocyte lysate assay. Thus, this improved micropurification method may be a suitable interface between analytical gel electrophoresis and further characterization or use of LPS.

S-form lipopolysaccharide (LPS), but not lipid A or R-chemo-type LPS, induces interleukin-6 production in vitamin D3-differentiated THP-1 cells

Bacterial lipopolysaccharide (LPS) induces the production of various inflammatory cytokines and the inducibility is considered attributable to the glycolipid part of LPS called lipid A. We report an in vitro model in which lipid A is not necessarily a minimal structure for the LPS activity. Vitamin D3-differentiated THP-1 cells, cultured human monocytic leukemia cells, produced a high level of interleukin-6 (IL-6) by stimulating LPS from Escherichia coli O111:B4, but not by stimulating synthetic E. coli-type lipid A (compound 506), E. coli Re mutant LPS (ReLPS), or alkali-treated LPS. The induction by LPS was inhibited by the anti-CD14 antibodies or by the synthetic lipid A precursor (compound 406). An alkali-treated LPS or compound 506 partially inhibited the LPS-induced IL-6 production. These facts suggest that lipid A alone is not sufficient for the IL-6-inducing activity, but the polysaccharide part in LPS contributes or acts as a co-factor for activation of differentiated THP-1 cells.

Immunostimulation by plant polyphenols: a relationship between tumor necrosis factor-alpha production and tannin structure

The ability of the naturally occurring tumoricidal ellagitannin coriariin A to stimulate secretion of both IL-1beta and TNF-alpha from human peripheral blood mononuclear cells has been demonstrated. Companion studies with the monomeric gallotannin beta-D-pentagalloylglucose and a synthesized dimeric gallotannin-ellagitannin hybrid suggest that TNF-alpha rather than IL-1beta is the causative agent in tannin-mediated antitumor action in vivo, in contrast to an ealier proposal.

Suppressive effects of serum on the LPS-induced production of nitric oxide and TNF-alpha by a macrophage-like cell line, WEHI-3, are dependent on the structure of polysaccharide chains in LPS

The effect of serum on LPS-induced activation of a murine macrophage-like cell line, WEHI-3, was examined. Foetal calf serum strongly inhibited the production of nitric oxide (NO) and TNF-alpha by LPS-stimulated WEHI-3 cells, while it enhanced the production of both by other macrophage-like cell lines, J774.1 and BAM3, on treatment with LPS. This suppressive effect of serum on WEHI-3 cells was most remarkable when the cells were stimulated with rough-chemotype LPS, Ra LPS, Rc LPS and Rd2 LPS. Foetal calf serum also inhibited TNF-alpha production by the same cells stimulated with high concentrations of smooth-form LPS (S LPS; > 1000 ng/mL). Serum-mediated suppression was also observed for expression of the TNF-alpha gene in Rc LPS-stimulated WEHI-3 cells. This suppressive effect of FCS was most remarkable during the 1-2 h before the addition of LPS, but it was not observed when FCS was added at 1 h after the addition of LPS, suggesting dependence on the time of FCS addition to LPS-stimulated cells. No significant difference was observed in the expression of CD14 on WEHI-3 cells cultured in the presence and absence of serum, suggesting that CD14 is not involved in the serum-mediated suppression of these LPS-responses. On the contrary, FCS showed enhancing effects on the production of NO and TNF-alpha by WEHI-3 cells stimulated with low concentrations (< 100 ng/mL) of S LPS and rough mutant Salmonella minnesota Re LPS. These results suggest that the ability of FCS to suppress LPS-induced activation of WEHI-3 cells in mainly dependent on the structure of polysaccharide chains and also on the concentration of LPS employed.

Lipopolysaccharides (LPS) of oral black-pigmented bacteria induce tumor necrosis factor production by LPS-refractory C3H/HeJ macrophages in a way different from that of Salmonella LPS

Some lipopolysaccharide (LPS) preparations from S- or R-form members of the family Enterobacteriaceae and oral black-pigmented bacteria (Porphyromonas gingivalis and Prevotella intermedia) are known to activate LPS-refractory C3H/HeJ macrophages. When contaminating proteins are removed from R-form LPS of Enterobacteriaceae by repurification, however, this ability is lost. In the present study, we investigated the capacity of LPS from P. gingivalis, P. intermedia, Salmonella minnesota, and Salmonella abortusequi to induce production of tumor necrosis factor (TNF) in gamma interferon-primed C3H/HeJ macrophages before and after repurification. P. abortusequi S-LPS was fractionated by centrifugal partition chromatography into two LPS forms: SL-LPS, having homologous long O-polysaccharide chains, and SS-LPS having short oligosaccharide chains. Prior to repurification, all LPS forms except SL-LPS induced TNF production in both C3H/HeJ and C3H/HeN macrophages. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed that repurification removed contaminating protein from the preparations, and repurified SS-LPS and S. minnesota Ra-LPS no longer stimulated TNF production in C3H/HeJ macrophages, although C3H/HeN macrophages remained responsive. In contrast, repurified oral bacterial LPS retained the capacity to induce TNF production in C3H/HeJ macrophages. Oral bacterial LPS preparations also were not antagonized by excess inactive, repurified SL-LPS; Ra-LPS; Rhodobacter sphaeroides lipid A, a competitive LPS antagonist, or paclitaxel, an LPS agonist, and they were comparatively resistant to polymyxin B treatment. Nevertheless, oral bacterial LPS was less toxic to D-galactosamine-treated C3H/HeN mice than was LPS from Salmonella. These findings indicate that the active molecule(s) and mode of action of LPS from P. gingivalis and P. intermedia are quite different from those of LPS from Salmonella.

Elution of lipopolysaccharides from polyacrylamide gels

A simple procedure for elution in water of bacterial lipopolysaccharides (LPS) from sodium dodecyl sulfate-polyacrylamide gels is described. It consists of the combination of three principal steps: first, highly sensitive on-gel LPS detection (1-10 ng/band) with zinc-imidazole (negative or reverse staining); second, washing of the individual LPS band in a solution of a zinc-complexing agent (e.g., 100 mM EDTA); and finally, elution of the LPS (100-200 microliters water for a 0.5-microgram LPS band) from gel microparticles for 3 h at room temperature. Using this procedure, we have successfully eluted a variety of LPS forms from Bordetella pertussis, Escherichia coli 0111:B4, E. coli K-235, Salmonella enteritidis, and Pseudomonas aeruginosa. Elution recovery of rough or semismooth LPS was about 70-80%, while that of smooth LPS was only about 10%. Eluted LPS was biologically active as tested by limulus amebocyte lysate and TNF-alpha assays.

Participation of CD14 in the phagocytosis of smooth-type Salmonella typhimurium by the macrophage-like cell line, J774.1

The role of CD14 in the phagocytosis and killing of microorganisms was investigated using macrophage-like cell lines, CD14-positive J774.1 cells and CD14-negative mutant J7.DEF.3 cells derived from J744.1 cells. The cells were infected with Salmonella typhimurium organisms of the smooth (S)-form LT2, mutant rough (R)-form TV148 or Staphylococcus aureus 248betaH. At 30 or 180 min incubation, the cells were washed and disrupted. Colony-forming units (CFUs) liberated from the disrupted cells were determined by quantitative cultivation, and the phagocytic index and killing rate were calculated. Both the phagocytic index and killing rate of J774.1 cells against LT2 organisms were greater than those of J7.DEF.3 cells. However, the index and rate of J774.1 cells against TV148 and 248betaH organisms were similar to those of the J7.DEF.3 cells. The phagocytosis of LT2 organisms by J774.1 cells was partially inhibited by S-form LPS (S-LPS) and anti-CD14 antibody, but not by R-chemotype LPS (R-LPS). These results suggest that CD14 participates in the phagocytosis of S-form Salmonella.