Regulation of fetal hemoglobin expression during hematopoietic stem cell development and its importance in bone metabolism and osteoporosis

We have shown that an altered tissue redox environment in mice lacking either murine beta Hemoglobin major (Hgbβ_maKO) or minor (Hgbβ_miKO) regulates inflammation. The REDOX environment in marrow stem cell niches also control differentiation pathways. We investigated osteoclastogenesis (OC)/osteoblastogenesis (OB), in bone cultures derived from untreated or FSLE-treated WT, Hgbβ_maKO or Hgbβ_miKO mice. Marrow mesenchymal cells from 10d pre-cultures were incubated on an osteogenic matrix for 21d prior to analysis of inflammatory cytokine release into culture supernatants, and relative OC:OB using (TRAP:BSP, RANKL:OPG) mRNA expression ratios and TRAP or Von Kossa staining. Cells from WT and Hgbβ_maKO mice show decreased IL-1β,TNFα and IL-6 production and enhanced osteoblastogenesis with altered mRNA expression ratios and increased bone nodules (Von Kossa staining) in vitro after in vivo stimulation of mRNA expression of fetal Hgb genes (Hgbε and Hgbβ_mi) by a fetal liver extract (FSLE). Marrow from Hgbβ_miKO showed enhanced cytokine release and preferential enhanced osteoclastogenesis relative to similar cells from WT or Hgbβ_maKO mice, with no increased osteoblastogenesis after mouse treatment with FSLE. Pre-treatment of WT or Hgbβ_maKO, but not Hgbβ_miKO mice, with other molecules (rapamycin; hydroxyurea) which increase expression of fetal Hgb genes also augmented osteoblastogenesis and decreased cytokine production in cells differentiating in vitro. Infusion of rabbit anti- Hgbε or anti- Hgbβ_mi, but not anti-Hgbα or anti- Hgbβ_ma into WT mice from day 13 gestation for 3 weeks led to attenuated osteoblastogenesis in cultured cells. We conclude that increased fetal hemoglobin expression, or use of agents which improve fetal hemoglobin expression, increases osteoblast bone differentiation in association with decreased inflammatory cytokine release.

Timothy grass pollen major allergen Phl p 1 activates respiratory epithelial cells by a non-protease mechanism

BACKGROUND

Group 1 allergens from grass pollen (e.g. Phl p 1, the major allergen of timothy grass Phleum pratense) cause IgE reactivity in about 95% of allergic subjects and exist in all grass species. The respiratory epithelium represents a first line of contact of the immune system with airborne allergens, functions as physical barrier and is an important immunological regulation system.

OBJECTIVE

The aim of this study was to investigate the interaction of Phl p 1 with human respiratory epithelium to elucidate the contribution of epithelial cells to the development of allergic reactions.

METHODS

Purified Phl p 1 was used to stimulate A549 cells and transient transfected HEK293 cells. mRNA level of different mediators were investigated by real-time PCR, release of the mediators was determined by ELISA. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) test and an ex vivo model of the murine trachea were used to investigate a potential proteolytic activity of Phl p 1.

RESULTS

Phl p 1 activates respiratory epithelial cells as measured by induction of IL-6, IL-8 and TGF-beta mRNA and release. Phl p 1, in contrast to Der p 1 from the house dust mite, does not exert proteolytic activity, as investigated by microscopic observation and MTT test. In an ex vivo model of the murine trachea we were able to show that Der p 1, in contrast to Phl p 1, enhances the transportation velocity of particles by the trachea, presumably by ATP released from the injured epithelium.

CONCLUSION

We conclude that under physiological conditions Phl p 1 affects tracheal epithelial cells through a non-proteolytic activity. Enhancement of TGF-beta expression induced by Phl p 1 together with the increased release of IL-6 and IL-8 might provide an indirect mechanism through which the allergen may cross the epithelial barrier and attracts immunocompetent cells.

Induction of tolerogenic vs immunogenic dendritic cells (DCs) in the presence of GM-CSF is regulated by the strength of signaling from monophosphoryl lipid A (MPLA) in association with glutathione and fetal hemoglobin gamma-chain

Previous studies showed a fetal sheep liver extract (FSLE), in association with monophosphoryl lipid A, MPLA (a bioactive component of lipid A of LPS), could interact to induce the development of dendritic cells (DCs) which regulated production of Foxp3+ Treg. This interaction was associated with an altered gene expression both of distinct subsets of TLRs and of CD200Rs. Prior studies had suggested that major interacting components within FSLE were gamma-chain of fetal hemoglobin (Hgbgamma) and glutathione (GSH). We investigated whether differentiation/maturation of DCs in vitro in the presence of either GM-CSF or Flt3L to produce preferentially either immunogenic or tolerogenic DCs was itself controlled by an interaction between MPLA, GSH and Hgbgamma. At low (approximately 10 microg/ml) Hgbgamma concentrations, DCs developing in culture with GSH and MPLA produced optimal stimulation of allogeneic CTL cell responses in vitro (and enhanced skin graft rejection in vivo). At higher concentrations (>40 microg/ml Hgbgamma) and equivalent concentrations of MPLA and GSH, the DCs induce populations of Treg which can suppress the induction of allogeneic CTL and graft rejection in vivo. These different populations of DCs express different patterns of mRNAs for the CD200R family. Addition of anti-TLR or anti-MD-1 mAbs to DCs developing in this mixture (Hgbgamma+GSH+MPLA), suggests that one effect of (GSH+Hgbgamma) on MPLA stimulation may involve altered signaling through TLR4.

An alteration in the levels of populations of CD4+ Treg is in part responsible for altered cytokine production by cells of aged mice which follows injection with a fetal liver extract

We have shown previously that a fetal sheep liver extract (FSLE) containing significant quantities of fetal ovine gamma globin chain (Hbgamma) and LPS injected into aged (>20 months) mice could reverse the altered polarization (increased IL-4 and IL-10 with decreased IL-2 and IFNgamma) in cytokine production seen from ConA stimulated lymphoid cells of those mice. The mechanism(s) behind this change in cytokine production were not previously investigated. We report below that aged mice show a >60% decline in numbers and suppressive function of both CD4(+)CD25(+)Foxp3(+) Treg and so-called Tr3 (CD4(+)TGFbeta(+)), and that their number/function is restored to levels seen in control (8-week-old) mice by FSLE. In addition, on a per cell basis, CD4(+)CD25(-)Treg from aged mice were >4-fold more effective in suppression of proliferation and IL-2 production from ConA-activated lymphoid cells of a pool of CD4(+)CD25(-)T cells from 8-week-old mice than similar cells from young animals, and this suppression by CD25(-)T cells was also ameliorated following FSLE treatment. Infusion of anti-TGFbeta and anti-IL-10 antibodies in vivo altered Treg development following FSLE treatment, and attenuated FSLE-induced alterations in cytokine production profiles.

Role of MIF and glutathione, in association with fetal ovine globin chain (Hbγ) and LPS, in induction of TNFα from cells of young and aged mice, and PBL from healthy human populations

Previous reports from our group have established that the fetal ovine gamma globin chain (Hbgamma) and LPS can synergize in the induction of pro-inflammatory cytokines, especially TNFalpha, from mouse and human leukocytes. A fetal sheep liver extract (FSLE) which was observed to have marked immunoregulatory properties in vivo and in vitro had independently been observed to contain significant amounts of each of these molecules. However, the biological activity of this extract (hereafter FSLE) was not explained solely by its content of Hbgamma and LPS, and independent analysis confirmed also the presence of migration inhibitory factor, MIF, and glutathione in FSLE. We have investigated whether MIF and the cellular anti-oxidant glutathione can further synergize with Hbgamma and LPS in TNFalpha induction from human cells in vitro, and mouse cells activated in vivo/in vitro. Our data show that indeed there is evidence for such a synergy. Treatment or mouse cells with FSLE produced an enhanced TNFalpha production which could be inhibited independently both by anti-Hbgamma and by anti-MIF, and optimally by a combination of these reagents.

Forming and immunological properties of some lipopolysaccharide–chitosan complexes

The complex formation of lipopolysaccharide (LPS) with chitosan (Ch) was demonstrated using sedimentation velocity analysis in the analytical ultracentrifuge, centrifugation in glycerol gradient and isopicnic centrifugation in cesium chloride. An addition of Ch to the Escherichia coli and Yersinia pseudotuberculosis LPS solutions was found to result in formation of the stable LPS-Ch complexes. The interaction is a complicated process and depends on time and reaction temperature, as well as on the molecular weight of chitosan. A stable LPS-Ch complex could be formed only after preliminary incubation of the initial components at an elevated temperature (37 degrees C). It should be noted that process of LPS complexation with Ch is accompanied by additional dissociating of LPS. The complex formation was shown to be a result not only of ionic binding, but also of other types of interactions. The interaction of Ch with LPS was shown to modulate significantly the biological activity of LPS. The LPS-Ch complex (1:5 w/w) was shown to possess much lower toxicity in a comparison with the parent LPS at injection to mice in the similar concentration. The LPS-Ch complex was shown to maintain an ability to induce of IL-8 and TNF, but induction of IL-8 and TNF biosynthesis by the LPS-Ch complex was lower than that by the parent LPS. The complex LPS-Ch, similarly to the parent LPS, was found stimulated the formation of the IL-8 in the dose-dependent manner in the human embryonal kidney cells (HEK 293 cells) transfected with TLR4 in combination with MD2.

The LPS receptor (CD14) links innate immunity with Alzheimer's disease

To rapidly respond to invading microorganisms, humans call on their innate immune system. This occurs by microbe-detecting receptors, such as CD14, that activate immune cells to eliminate the pathogens. Here, we link the lipopolysaccharide receptor CD14 with Alzheimer's disease, a severe neurodegenerative disease resulting in dementia. We demonstrate that this key innate immunity receptor interacts with fibrils of Alzheimer amyloid peptide. Neutralization with antibodies against CD14 and genetic deficiency for this receptor significantly reduced amyloid peptide induced microglial activation and microglial toxicity. The observation of strongly enhanced microglial expression of the LPS receptor in brains of animal models of Alzheimer's disease indicates a clinical relevance of these findings. These data suggest that CD14 may significantly contribute to the overall neuroinflammatory response to amyloid peptide, highlighting the possibility that the enormous progress currently being made in the field of innate immunity could be extended to research on Alzheimer's disease.

Inhibition of bladder carcinoma cell adhesion by oligopeptide combinations in vitro and in vivo

PURPOSE

A presumed reason for the high recurrence rate of superficial bladder cancer after transurethral tumor resection is the reimplantation of tumor cells. Because tumor cell adhesion to the extracellular matrix is mediated by integrin molecules, we tested specific integrin receptor blocking oligopeptides to prevent this mechanism.

MATERIALS AND METHODS

An in vitro cell adherence assay with various bladder cancer cell lines and extracellular matrices, including fibronectin, collagen type I, laminin and combinations, was used to analyze the inhibition of tumor cell adhesion by the matrix specific oligopeptides GRGDS, DGEA and EILDV. In therapeutic in vivo experiments the orthotopic murine bladder tumor model MB49 was used. The ability of oligopeptides to interfere with tumor cell adhesion and consecutive tumor outgrowth was evaluated and compared with that of nonspecific peptides, commercially available irrigation fluid and single dose epirubicin chemotherapy.

RESULTS

In vitro fibronectin specific oligopeptides showed a concentration dependent inhibition of tumor cell adherence to fibronectin, whereas adhesion to laminin, collagen and combined matrices was not inhibited. In contrast, combinations of integrin receptor blocking oligopeptides were highly active. In vivo local tumor take was not affected by irrigation fluid, nonspecific peptides or monospecific oligopeptides alone, whereas the combination of the 3 oligopeptides effectively inhibited tumor outgrowth.

CONCLUSIONS

Combining oligopeptides with various specificities significantly inhibited tumor cell adhesion and tumor outgrowth. Application of this principle in a clinical setting may be an effective method for reducing the recurrence rate of superficial bladder cancer.

The biology of endotoxin

Endotoxin (lipopolysaccharide, LPS) is the major component of the outer leaflet of Gram-negative bacteria and has profound immunostimulatory and inflammatory capacity. The septic shock syndrome caused by endotoxin still has an unacceptably high mortality rate and, owing to increasing numbers of resistant strains, remains an ongoing threat throughout the world. However, the past years have provided new insights especially into the receptors of the innate immune system that are involved into the recognition of LPS and the initial signal transduction pathways that are engaged after the primary recognition on the cell surface. The knowledge about the molecular basis for the responses to endotoxin may eventually lead to the development of new drugs to fight the fatal effects of bacterial infections.

Lipopolysaccharide and ceramide docking to CD14 provokes ligand-specific receptor clustering in rafts

The glycosylphosphatidylinositol-anchored receptor CD14 plays a major role in the inflammatory response of monocytes to lipopolysaccharide. Here, we describe that ceramide, a constituent of atherogenic lipoproteins, binds to CD14 and induces clustering of CD14 to co-receptors in rafts. In resting cells, CD14 was associated with CD55, the Fcgamma-receptors CD32 and CD64 and the pentaspan CD47. Ceramide further recruited the complement receptor 3 (CD11b/CD18) and CD36 into proximity of CD14. Lipopolysaccharide, in addition, induced co-clustering with Toll-like receptor 4, Fcgamma-RIIIa (CD16a) and the tetraspanin CD81 while CD47 was dissociated. The different receptor complexes may be linked to ligand-specific cellular responses initiated by CD14.

Structural and biological characterisation of a novel tetra-acyl lipid A from Escherichia coli F515 lipopolysaccharide acting as endotoxin antagonist in human monocytes

We here report on the structural analysis of a novel tetra-acyl lipid A (LA (tetra) ) isolated from Escherichia coli deep rough (Re)-mutant strain F515. In addition to the biologically active hexa-acyl E. coli-type lipid A (compound 506), this incompletely acylated lipid A was found to be also present in the native LPS. Its structure was studied without further derivatisation by chemical analysis, matrix-assisted laser desorption/ionization mass spectrometry, and one- and two-dimensional (1)H- and (13)C-NMR spectroscopy. It was found to be structurally distinct from the tetra-acyl lipid A biosynthetic precursor Ia (compound 406) in lacking the primary (R)-3-hydroxytetradecanoic acid 14:0(3-OH) in position 3' ester-linked to the 'non-reducing' glucosamine (GlcN II). The hydroxyl group at the (R)-3-hydroxytetradecanoic acid attached to position 2' of GlcN II was found to be substituted by dodecanoic acid (12:0), thus forming a dodecanoyloxytetradecanoyl residue 14:0[3-O(12:0)]. The acylation pattern at the 'reducing' GlcN I was identical to that of compound 406 in having two primary (R)-3-hydroxy tetradecanoic acid residues [14:0(3-OH)] attached to positions 3 (ester-linked) and 2 (amide-linked), respectively. In human mononuclear cells (hMNC) the new LA (tetra) antagonized LPS-induced release of interleukin-1 (IL-1), interleukin-6 (IL-6), and tumor necrosis factor (TNF) in a dose-dependent manner with identical antagonistic potency as compared with compound 406. Also like compound 406, it was found to be an agonist in murine macrophage-like J774.1 cells.

Decay-accelerating factor (DAF/CD55) is a functional active element of the LPS receptor complex

Previously, we identified an 80 kDa membrane protein (LMP80) that is capable of binding to LPS and lipid A in the presence of LBP and sCD14. LMP80 could also be detected after immuno-coprecipitation of cell membranes with LPS and lipid A, indicating a physical contact of LMP80 and LPS/lipid A. Further analysis and peptide sequencing revealed that LMP80 is identical to CD55 (decay accelerating factor, DAF), a regulatory molecule of the complement cascade. Transfection of LPS-hyporesponsive Chinese hamster ovary (CHO) cells with human CD55 resulted in the translocation of NF-B upon stimulation with LPS or lipid A. Our results demonstrate a new functional role of CD55 as a molecule able to mediate LPS-induced activation of cells that may be part of a multimeric LPS receptor complex.

The interaction of human peripheral blood eosinophils with bacterial lipopolysaccharide is CD14 dependent

Bacterial lipopolysaccharide (LPS, endotoxin) is a ubiquitous component of dust and air pollution and is suspected to contribute after inhalation to an activation of eosinophils in bronchial tissues of asthmatic patients, provoking inflammatory and allergic processes. We were therefore interested in the interaction of eosinophil granulocytes with LPS and have examined the activation of and uptake to human peripheral blood eosinophils by LPS. Eosinophils were stimulated by LPS and the endotoxic component lipid A and the release of tumor necrosis factor alpha (TNF-alpha) and of the eosinophil-specific granule protein eosinophil cationic protein (ECP) was estimated. The results show induction of TNF-alpha and ECP-release by LPS and lipid A in a dose-dependent manner. Anti-CD14 monoclonal antibody (moAb) (clone MEM-18) and the synthetic lipid A partial structure 406 blocked the release of TNF-alpha and ECP by LPS-stimulated eosinophils. Studies with radioactively labeled LPS showed dose-dependent uptake of (3)H-LPS to eosinophils. The (3)H-LPS uptake was found to be specific because preincubation with unlabeled LPS, compound 406 and also anti-CD14 antibodies inhibited uptake of (3)H-LPS to eosinophil granulocytes. By flow cytometry using anti-CD14 moAb and by reverse transcriptase-polymerase chain reaction (RT-PCR) technique, CD14 expression was detectable. Furthermore, messenger RNA (mRNA) expression of Toll-like receptors (TLR) 2 and TLR 4 was detected, indicating the presence of these CD14 coreceptors. The results indicate that eosinophils can take up LPS and can be stimulated by LPS in a CD14-dependent manner. Hence, in addition to allergens, eosinophils interact with endotoxin, a process that possibly exacerbates ongoing inflammatory and allergic processes.

Induction of proliferation and cytokine production in human T lymphocytes by lipopolysaccharide (LPS)

Lipopolysaccharide (LPS), also known as endotoxin, is a compound of the cell wall of Gram-negative bacteria, which has been demonstrated to induce inflammatory reactions in vitro as well as in vivo, including lethal shock. A great number of different cells have been documented to be reactive to LPS, e.g. monocytes/macrophages, vascular cells, polymorphonuclear cells, and even B lymphocytes. We have now established that T lymphocytes could also contribute to an inflammatory reaction to LPS. LPS is a potent inducer of human T-lymphocyte proliferation and cytokine production. The activation of T lymphocytes by LPS requires direct cell-to-cell contact with viable accessory monocytes. This interaction was found to be MHC-unrestricted, but strongly dependent on costimulatory signals provided by B7/CD28 interactions. The frequency of responding T lymphocytes is less than 1:1000. A very exciting finding was that not only monocytes, but also CD34+ hematopoietic stem cells, which circulate in peripheral blood in very low frequency, exert essential accessory cell activity during stimulation of T lymphocytes by LPS. In contrast, the response of T lymphocytes to conventional recall antigens is not controlled by blood stem cells. These conclusions are based on the observation that depletion of CD34-positive blood stem cells resulted in a complete loss of LPS-induced T-lymphocyte stimulation. Addition of CD34-enriched blood stem cells led to a recovery of reactivity of T lymphocyte to LPS. The characteristics of T-lymphocyte activation indicate that LPS is neither active as a mitogen, or as a superantigen, or as a classical antigen, but may activate T lymphocyte through a new, so far undescribed, mechanism. Furthermore, the involvement of hematopoietic blood stem cells in the activation of T lymphocytes by LPS demonstrates a role of these cells in inflammatory and immunological events.

In vitro generation of bacillus Calmette-Guérin-activated killer cells

Tumor regression induced in cancer patients by local instillation of bacillus Calmette-Guérin (BCG) into the bladder is considered to be mediated by cellular immune and inflammatory reactions. In an attempt to elucidate which of these effects are relevant to tumoricidal activity, an in vitro system was employed in which the immunostimulatory effects of BCG could be studied. This report describes the induction of BCG-activated killer (BAK) cells, which effectively lyse bladder tumor cells. Human peripheral blood mononuclear cells (PBMC) were stimulated with viable and sonicated BCG (v-BCG and s-BCG, respectively) to generate BAK cells. Cytotoxicity of BAK cells was comparable with the cytotoxicity exerted by lymphokine-activated killer (LAK) cells generated by interferon (IFN)-gamma but did not reach the level of interleukin-2 (IL-2)-generated LAK cells. Induction of BAK cells was possible only with v-BCG and not with s-BCG. By depletion and enrichment of defined cell populations, the cytotoxic potential of BAK cells could be attributed to a population of CD8(+) and CD56(+) double-positive lymphocytes. Macrophages and CD4(+) cells were required for the induction of killing activity but had no such activity by themselves. Furthermore, the presence of IFN-gamma and IL-2 in the supernatants harvested during the generation of BAK cells was demonstrated. Monoclonal antibodies neutralizing these cytokines abolished BCG-mediated cytotoxicity. From these results, it is concluded that the known beneficial effect of local instillation of BCG on maintenance of the relapse-free state in superficial bladder cancer may be due to local generation of BAK cells.

Reduction of side effects of intravesical therapy with bacille Calmette-Guérin by pentoxifylline?--an in vitro approach

Immunotherapy with intravesical bacille Calmette-Guérin (BCG) is the treatment of choice against superficial bladder cancer recurrences. However, this therapy is associated with side effects that are considered to be the result of inflammatory cytokines. Since pentoxifylline is known to interfere with the production of cytokines, this drug was tested in vitro with regard to a later clinical application in BCG-treated patients. The cytokine release and the cytotoxicity of interleukin-2 or BCG-stimulated mononuclear cells were analyzed, and the growth of BCG under the influence of pentoxifylline was assayed. The results showed an inhibition of cytokine release of stimulated mononuclear cells. The cytotoxicity of BCG-stimulated mononuclear cells but not of lymphokine-stimulated mononuclear cells against bladder carcinoma cells was significantly inhibited. Restimulation with fresh BCG restored cytotoxicity. Direct coincubation of BCG and pentoxifylline resulted in a reduction of mycobacterial metabolism. From these data, we conclude that the use of pentoxifylline to reduce BCG-related side effects should be tested further in a clinical study.

Lipopolysaccharide and peptidoglycan: CD14-dependent bacterial inducers of inflammation

Surface structures of bacteria contribute to the microbial pathogenic potential and are capable of causing local and generalized inflammatory reactions. Among these factors, endotoxin and peptidoglycan are of particular medical importance. Both toxic bacterial polymers are now recognized to interact with the same cellular receptor, the CD14 molecule, which is expressed on different types of immune cells, in particular, monocytes/macrophages. The interaction between these bacterial activators and CD14 leads to the production of endogenous mediators such as tumor necrosis factor alpha, interleukin 1 (IL-1), and IL-6, which are ultimately responsible for phlogistic responses. The fact that CD14 recognizes not only endotoxin and peptidoglycan but also other glycosyl-based microbial polymers suggests that this cellular surface molecule represents a lectin.

Binding of lipopolysaccharide (LPS) to CHO cells does not correlate with LPS-induced NF-kappaB activation

Activation of myeloid cells by lipopolysaccharide (LPS) is a key event in the development of gram-negative sepsis. One crucial step within this process is the binding of LPS to CD14. CD14 is a glycosylphosphatidylinositol (GPI)-anchored membrane protein requiring at least one additional membrane-spanning molecule for signal transduction. It is not clear whether the function of CD14 is to merely catalyze LPS binding, followed by the interaction of LPS with the signal transducer, or whether CD14 has a more specific function and may be a part of the signaling complex. To address this question we generated Chinese hamster ovary (CHO) cells expressing a human GPI-anchored form of LPS-binding protein (mLBP) to substitute for CD14 as LPS acceptor molecule. By comparison of CHO / mLBP with CHO / vector and CHO / CD14 cells we found that expression of GPI-linked LBP results in an enhanced binding of LPS but not in an increase in cell activation as determined by translocation of NF-kappaB. Furthermore, excess of recombinant soluble LBP resulted also in increased LPS binding without affecting NF-kappaB translocation. These data show that LPS binding alone is not sufficient to induce signaling. We conclude that CD14 is more than a catalyst for LPS binding: it seems to be directly involved in LPS signaling and thus appears to be an essential part of the signaling complex.

Differential impact of substitution of amino acids 9-13 and 91-101 of human CD14 on soluble CD14-dependent activation of cells by lipopolysaccharide

The soluble form of the endotoxin receptor CD14 is required for the LPS-induced activation of cells lacking membrane-bound CD14. It has been shown that a deletion mutant of human CD14 consisting of the N-terminal 152 amino acids has the capacity to mediate the stimulation of different cell types by LPS. To identify the structural domains of the molecule related to this functional property, we screened a set of alanine substitution mutants using CD14-negative U373 astrocytoma cells. We show that 3 of 18 soluble mutants of human CD14 failed to mediate the LPS-induced IL-6 production in U373 cells. These mutants were located in two regions of the molecule (aa 9-13 and 91-101) that are not essential for LPS binding. In addition, the mutants had a reduced capacity to mediate LPS-stimulated IL-6 production in human vascular endothelial and SMC. In contrast, the potential of sCD14(91-94,96)A, and sCD14(97-101)A to signal LPS-induced activation of human PBMC was not significantly reduced. These results show that the regions 9-13 and 91-101 are involved in the sCD14-dependent stimulation of cells by LPS but that the mechanisms by which different cell types are activated may not be identical.

Bacillus-Calmette-Guérin (BCG) and 3D tumors: an in vitro model for the study of adhesion and invasion

PURPOSE

To study adhesion, penetration and internalization of BCG and effector-cells to and into three-dimensional in vitro cell aggregates from benign and malignant urothelial origin mimicking small in vitro tumors.

MATERIALS AND METHODS

Multicellular spheroids (MCS) were generated by "liquid-overlay" technique. Adhesion and penetration of viable FITC-labelled BCG into MCS from urothelial cancer cell lines and normal urothelial cells was studied by electron microscopy (TEM) and fluorescence microscopy. Spheroid growth during BCG-co-incubation was determined by light microscopy. Peripheral blood mononuclear cells (PBMC) were stimulated with BCG to generate BCG-activated-killer (BAK) cells. The infiltration of these effectors and of lymphokine-activated killer (LAK) cells into MCS was examined at different intervals by means of immunohistochemistry. The resulting cytotoxicity was judged in a 3H-l-methionine release assay.

RESULTS

BCG adhered to MCS from tumor cells but not to benign cell MCS. Intracellular internalization of the bacteria was detectable in superficial tumor cell-layers (1-5) whereas BCG was not found in deeper layers. Proliferation of malignant MCS was reduced in the presence of BCG. Benign MCS showed contact inhibition growth arrest, which was not altered by BCG. BAK and LAK effector cells both infiltrated tumor cell MCS as opposed to unstimulated PBMC. In contrast to LAK cells, BAK cells did not infiltrate into benign cell MCS and were not cytotoxic towards them.

CONCLUSION

With regard to the clinical situation the selective adhesion and internalization of BCG to malignant cells might explain why BCG has been rarely found in follow-up biopsies in tumor free patients. More interestingly, the selective adhesion of BCG to and infiltration of BAK effector cells into malignant cell spheroids suggests a selective mode of action of BCG.

The dual role of lipopolysaccharide as effector and target molecule

Lipopolysaccharides (LPS) are major integral components of the outer membrane of Gram-negative bacteria being exclusively located in its outer leaflet facing the bacterial environment. Chemically they consist in different bacterial strains of a highly variable O-specific chain, a less variable core oligosaccharide, and a lipid component, termed lipid A, with low structural variability. LPS participate in the physiological membrane functions and are, therefore, essential for bacterial growth and viability. They contribute to the low membrane permeability and increase the resistance towards hydrophobic agents. They are also the primary target for the attack of antibacterial drugs and proteins such as components of the host's immune response. When set free LPS elicit, in higher organisms, a broad spectrum of biological activities. They play an important role in the manifestation of Gram-negative infection and are therefore termed endotoxins. Physico-chemical parameters such as the molecular conformation and the charges of the lipid A portion, which is responsible for endotoxin-typical biological activities and is therefore termed the 'endotoxic principle' of LPS, are correlated with the biological activity of chemically different LPS.

The internalization time course of a given lipopolysaccharide chemotype does not correspond to its activation kinetics in monocytes

The prerequisites for the initiation of pathophysiological effects of endotoxin (lipopolysaccharide [LPS]) include binding to and possibly internalization by target cells. Monocytes/macrophages are prominent target cells which are activated by LPS to release various pro- and anti-inflammatory mediators. The aim of the present study was to establish a new method to determine the binding and internalization rate of different LPS chemotypes by human monocytes and to correlate these phenomena with biological activity. It was found that membrane-bound LPS disappears within hours from the surface being internalized into the cell. Further, a correlation between the kinetics of internalization and the length of the sugar chain as well as an inverse correlation between the time course of internalization and LPS hydrophobicity was revealed. Comparison of the internalization kinetics of different LPS chemotypes with kinetics of tumor necrosis factor alpha release and kinetics of oxidative burst did not reveal any correlation of these parameters. These findings suggest that cellular internalization of and activation by LPS are mechanisms which are independently regulated.

Identification of the 80-kDa LPS-binding protein (LMP80) as decay-accelerating factor (DAF, CD55)

The activation of immunocompetent cells by lipopolysaccharide (LPS) during severe Gram-negative infections is responsible for the pathophysiological reactions, possibly resulting in the clinical picture of sepsis. Monocytes recognize LPS mainly through the LPS receptor CD14, however, other cellular binding structures have been assumed to exist. In previous studies, we have described an 80-kDa LPS-binding membrane protein (LMP80), which is present on human monocytes as well as endothelial cells. Here we demonstrate that LMP80 is widely distributed and that it forms complexes together with LPS and sCD14. Furthermore, we report on the biochemical purification of LMP80 and its identification as decay-accelerating factor, CD55, by amino acid sequencing and cloning techniques. Our results imply a new feature of CD55 as a molecule which interacts with LPS/sCD14 complexes. However, the involvement of CD55 in LPS-induced signaling remains to be elucidated.

CD34(+) hematopoietic stem cells exert accessory function in lipopolysaccharide-induced T cell stimulation and CD80 expression on monocytes

CD34(+) hematopoietic stem cells, which circulate in peripheral blood with very low frequency, exert essential accessory function during lipopolysaccharide (LPS)-induced human T lymphocyte activation, resulting in interferon gamma production and proliferation. In contrast, stimulation of T cells by "conventional" recall antigens is not controlled by blood stem cells. These conclusions are based on the observation that depletion of CD34(+) blood stem cells results in a loss of LPS-induced T cell stimulation as well as reduced expression of CD80 antigen on monocytes. The addition of CD34-enriched blood stem cells resulted in a recovery of reactivity of T cells and monocytes to LPS. Blood stem cells could be replaced by the hematopoietic stem cell line KG-1a. These findings may be of relevance for high risk patients treated with stem cells or stem cell recruiting compounds and for patients suffering from endotoxin-mediated diseases.

Tissue factor expression of human monocytes is suppressed by lysophosphatidylcholine

The expression of tissue factor (TF), the principal initiator of coagulation, is increased during inflammation and atherosclerosis. Both conditions are promoted by lysophosphatidylcholine (lysoPC). We observed in the present study that lysoPC (1 to 10 micromol/L) dose-dependently reduced TF activity in human monocytes, as elicited by lipopolysaccharide (LPS). Lysophosphatidylethanolamine (lysoPE) and other lysophospholipids did not affect LPS-induced TF activity of human monocytes. TF antigen expression as elicited by LPS was also lowered by lysoPC. Phospholipid analyses indicated a selective increase in the lysoPC content of the monocytes after preincubation with the lysophospholipid. LysoPC inhibited the TF activity of Mono Mac-6 cells to a similar extent as in the monocytes. LPS binding to plasma membrane receptors and internalization of LPS into monocytes were not affected by lysoPC. In contrast, LPS-mediated nuclear binding of nuclear factor-kappaB/Rel to a TF-specific kappaB site was inhibited by lysoPC. Induction of TF mRNA expression by LPS tended to be partially reduced by the lysophospholipid. Preincubation with lysoPC increased monocytic cAMP levels. Inhibition of adenylyl cyclase by pretreatment with 2'-deoxy-3'-adenosine monophosphate partially reversed the inhibition of TF activity promoted by lysoPC. In conclusion, lysoPC markedly decreases LPS-mediated TF expression of human monocytes, the effect probably being mediated by both transcriptional and posttranscriptional mechanisms. LysoPC may thus attenuate activation of coagulation during inflammation and atherosclerosis.

Components of gut bacteria as immunomodulators

In 1885 Louis Pasteur was the first to propose that the human immune system may be influenced by microorganisms. A large body of data has since been accumulated proving this assumption to be correct. Bacteria constitute the main constituents of the microbial flora of the human digestive tract and compounds of the bacterial cell wall have been shown to play an important role in the interaction of microbes with higher organisms. These components include peptidoglycan (PG) and lipopolysaccharide (LPS) of gram-negative bacteria. Both types of molecules are potent activators of the human immune system and exert their activity through the induction of endogenous mediators which are endowed with biological activity. This review focuses on the structure and activity of LPS and PG and illustrates how these bacterial factors stimulate the immune cells resulting in desired physiological or dramatic pathophysiological responses of the host organism.

ADP-ribosylation: role in LPS-induced phosphorylation of two cytosolic proteins (p36/38) in monocytes

Human monocytes respond to LPS by releasing proinflammatory cytokines such as TNF-alpha, IL-1 and IL-6. Here we show that inhibitors of ADP-ribosylation namely nicotinamide and meta-iodobenzylguanidine prevent production of TNF-alpha and IL-6 at the protein and mRNA level. The inhibitors also influence the LPS-induced phosphorylation pattern of cytosolic proteins. They consistently lead to changes of the phosphorylation state of two proteins with an apparent molecular mass of 36 kDa and 38 kDa. The changes are both time and dose dependent. The data suggest that the conditions leading to altered phosphorylation of p36/38 may correlate with conditions initiating and regulating TNF-alpha and IL-6 production.

Stimulation of human T lymphocytes by LPS is MHC unrestricted, but strongly dependent on B7 interactions

Recently, we have shown that LPS is a potent inducer of human T cell proliferation and lymphokine production. However, the activation of T cells by LPS has been demonstrated to be monocyte dependent and to require direct cell-to-cell contact. Here, we investigated the role of monocytes as accessory cells and the requirement for costimulatory signals in more detail. We found that the accessory cell activity of monocytes during LPS-induced T cell proliferation is characterized by the following features: LPS-primed monocytes are competent stimulators of T cell proliferation; interaction of LPS with monocytes during the priming step is dependent on CD14 and is sensitive to ammonia; monocyte/T cell interactions are not MHC restricted but are strongly dependent on interactions of CD28 and/or CTLA-4 on T cells and their ligands CD80 and/or CD86 on monocytes. CD80 seems to be crucial for the activation of T cells by monocytes, since monocytes expressing CD86 but not CD80 after LPS stimulation were unable to stimulate T cells; IL-12, at least as a costimulatory factor, but not IL-15, is important in LPS-induced T cell proliferation. Taken together, our results indicate that LPS acts neither as a mitogen, nor as a superantigen, nor as an Ag. The activation of human T cells by LPS requires the help of accessory functions by primed monocytes and is MHC unrestricted but needs costimulatory signals via CD28 and/or CTLA-4.

Molecular mechanisms of sepsis

Today a great number of problems in the field of bacterial sepsis remain to be solved. Understanding the molecular mechanisms of one of the most important bacterial products in the pathogenesis of sepsis - endotoxin may contribute to innovative and more effective therapies. Therefore, this review focuses on the structural and functional elements of endotoxin, its interaction with immune cells, and its biological activity. Finally, other bacterial components and their impact on sepsis are discussed.

CD26 (dipeptidyl peptidase i.v.) on human T lymphocytes does not mediate adhesion of these cells to endothelial cells or fibroblasts

We have examined the role of CD26 (dipeptidyl peptidase IV) in the adhesion of resting and activated T lymphocytes to endothelial cells and fibroblasts. For this purpose, we ran a short-time adhesion assay under different strategies: Adhesion of T lymphocytes was determined in the presence of different anti-CD26 monoclonal antibodies, or in the presence of synthetic inhibitors of the enzymatic function of CD26. In addition, the expression of CD26 on T lymphocytes, which were adherent to endothelial cells or fibroblasts, was performed by flow cytometric analysis. We found that the anti-CD26 monoclonal antibodies tested here were not able to inhibit T cell adhesion to monolayers of endothelial cells or fibroblasts. Secondly, synthetic inhibitors of the enzymatic function of CD26 had no effect on the adhesion of T lymphocytes to endothelial cells or fibroblasts. Furthermore, CD26-positive T cells were not accumulated in the adherent population. These results suggest that CD26 on T lymphocytes plays no role in T cell adhesion to endothelial cells or fibroblasts.

Structural elucidation and monokine-inducing activity of two biologically active zwitterionic glycosphingolipids derived from the porcine parasitic nematode Ascaris suum

The isolated neutral glycosphingolipid fraction from the pig parasitic nematode, Ascaris suum, was fractionated by silica gel chromatography to yield a neutral and a zwitterionic glycosphingolipid fraction, the latter of which mainly contained two zwitterionic glycosphingolipids termed components A and C. Preliminary chemical characterization with hydrofluoric acid treatment and immunochemical characterization with a phosphocholine-specific monoclonal antibody indicated that both components contained phosphodiester substitutions: phosphocholine for component A, and phosphocholine and phosphoethanolamine for component C. Both components were biologically active in inducing human peripheral blood mononuclear cells to release the inflammatory monokines tumor necrosis factor alpha, interleukin 1, and interleukin 6. Component A was the more bioactive molecule, and its biological activity was abolished on removal of the phosphocholine substituent by hydrofluoric acid. The glycosphingolipid components were structurally analyzed by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, liquid secondary ion mass spectrometry, methylation analysis, 1H NMR spectroscopy, exoglycosidase cleavage, and ceramide analysis. Their chemical structures were elucidated to be (see Structure I below), [structure: see text] The carbohydrate moiety oligosaccharide core was characterized as belonging to the arthro series of protostomial glycosphingolipids. The ceramide moiety was distinguished by (R)-2-hydroxytetracosanoic acid as the dominant fatty acid species and by the C17 iso-branched sphingosine and sphinganine bases, 15-methylhexadecasphing-4-enine and 15-methylhexadecasphinganine, respectively.

Actin: a target of lipopolysaccharide-induced phosphorylation in human monocytes

We have previously reported that lipopolysaccharide (LPS) causes altered phosphate labelling of cytosolic proteins of 36 kDa and 38 kDa (p36/38) and that inhibition of phosphorylation is accompanied by a loss of cytokine production. Here we have purified the two phosphorylated proteins via two-dimensional polyacrylamide gel electrophoresis. P 36 was found to consist of two proteins p36a and p36b. The proteins were analysed by matrix-assisted laser desorption ionization (MALDI) mass spectrometry and p36b was identified as gamma-actin, p36a as beta/gamma-actin. The ability of LPS to cause altered phosphate labelling of beta/gamma-actin suggests a participation of the microfilament network in LPS-induced monocyte activation.

Detection of lipopolysaccharide (LPS)-binding membrane proteins by immuno-coprecipitation with LPS and anti-LPS antibodies

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

Effects of colony-stimulating factors on cellular cytotoxicity

Colony-stimulating factors (CSF) are used clinically in the treatment of chemotherapy-induced myelosuppression and in support of bone marrow transplantation. As CSF are known to have pleiotropic functions, their effects on cellular cytotoxicity were analysed in vitro against bladder carcinoma cell lines. By means of an L-[3H]methionine-release assay, the cytotoxicity of peripheral blood mononuclear cells against the natural-killer(NK)-cell-resistant bladder carcinoma cell lines BT-A and SBC-7 was measured using different effector/target-cell ratios. Costimulatory effects of granulocyte-colony-stimulating factor (G-CSF), granulocyte/macrophage colony-stimulating factor (GM-CSF), interleukin-3 (IL-3) and stem cell factor (SCF) on the generation of lymphokine-activated killer (LAK), bacillus Calmette-Guérin-activated killer (BAK) and natural killer (NK) cell cytotoxicity were investigated in this assay. Furthermore, the effect of CSF on proliferation of urothelial tumor cells in vitro was determined by a [3H]thymidine DNA-labelling technique. GM-CSF, but not G-CSF, IL-3 or SCF, was able to increase NK, BAK and LAK cytotoxicity in a dose-dependent manner. No acceleration of carcinoma cell proliferation was evident under the conditions of our assay. These data indicate the costimulatory effect of GM-CSF on cellular cytotoxicity, which might be used for immunotherapeutic purposes.

Specific binding of soluble peptidoglycan and muramyldipeptide to CD14 on human monocytes

Previously, we were able to show that soluble peptidoglycan (sPG)-induced monokine production in human peripheral monocytes is inhibited by anti-CD14 monoclonal antibodies and by lipid A partial structures. This suggested but did not prove that monocytic surface protein CD14 is involved in the activation of human monocytes not only by cell wall components of gram-negative bacteria such as lipopolysaccharide (LPS) but also by cell wall components of gram-positive bacteria such as sPG. In the present study, we provide experimental evidence that CD14 indeed constitutes a binding site for sPG recognition and activation of human monocytes. The results show that fluorescein isothiocyanate-sPG (FITC-sPG) binds to human monocytes in a saturable, dose-dependent, and specific manner. For maximal binding, 2 to 3 microg of FITC-sPG per ml was sufficient, and this binding is completed within 90 min; about 40% of the binding is completed within the first 3 min. The FITC-sPG binding is considered specific because unlabeled sPG and also muramyldipeptide (MDP), the minimal bioactive structure of sPG, inhibit the binding of sPG to monocytes in a dose-dependent manner. This specific binding was also inhibited by an anti-CD14 monoclonal antibody, LPS, and lipid A partial structure compound 406. Direct evidence for an interaction of sPG with CD14 is provided by experiments involving native polyacrylamide gel electrophoresis that showed a shift of the electrophoretic mobility of CD14 by LPS as well as by sPG. These results allow the conclusion that sPG binds directly to CD14, that MDP represents the active substructure of sPG, and that CD14 may be a lectin-like receptor which plays a key role in cellular stimulation by bioactive components of not only gram-negative but also gram-positive bacteria.

The effect of lubricants on viability of bacillus Calmette-Guerin for intravesical immunotherapy against bladder carcinoma

PURPOSE

The viability of bacillus Calmette-Guerin (BCG) is crucial for induction of a local immune response and for effective therapy of recurrent superficial bladder carcinoma. During intravesical instillation of BCG lubricants are administered to assist catheterization, which contain bacteriostatic components that may interfere with the viability of mycobacteria. To verify this assumption, 5 commercially available lubricants were analyzed with regard to inhibition of viable BCG growth.

MATERIALS AND METHODS

Five different lubricants and their components were co-incubated with Connaught strain BCG and the resultant growth of BCG was assessed. To prove the significant passage of lubricants into the bladder, fluid was recovered from the bladder after catheterization, analyzed with regard to the bacteriostatic effect and compared to normal urine of different acidity.

RESULTS

Significant impairment of BCG viability, dependent on dosage and time of co-incubation, was noted with all lubricants analyzed. Several components, namely lidocaine hydrochloride, glyceryl stearate, propyl-4-hydroxy-benzoate and chlorhexidine digluconate, were identified as responsible for this inhibition. Fluid recovered from the bladder after lubricant assisted catheterization also showed an inhibitory effect, indicating significant mixture of the instillate with lubricants.

CONCLUSIONS

Generous use of lubricants to assist catheterization during intravesical BCG therapy will result in a clinically significant decrease in the number of intravesically instilled viable mycobacteria. For this reason, during intravesical immunotherapy with BCG only small amounts of lubricants should be used for urethral catheterization, and use of catheters not requiring lubricants should be considered.

Alterations in structure and cellular localization of molecular forms of DP IV/CD26 during T cell activation

Dipeptidyl peptidase IV (DP IV, CD26), known as an activation marker of T lymphocytes, is a proline-specific protease thought to be involved in the regulation of the immune response. The physiological role of dipeptidyl peptidase IV in the immune system and the molecular events of lymphocyte activation mediated by this enzyme are only partly established. Former results suggested the occurrence of different molecular forms of DP IV in distinct human sources. As yet it has been unknown whether DP IV from human hematopoietic cells also appears in different forms and whether similar structural modifications are involved in functional processes of the regulation of the immune response. Here we describe that lymphocytic DP IV/CD26 occurs in various molecular forms and that some of them are associated with the activation process. In cell lysates of mitogen-activated lymphocytes at least 5 enzymatically active DP IV forms and up to 11 immunoreactive molecular forms of this enzyme with isoelectric points between pH 3.5 and 5.9 were discernible. Corresponding analyses of soluble and membrane cell fractions of human lymphocytes showed significant differences in the staining pattern of molecular DP IV structures. After mitogenic stimulation a special molecular form of DP IV arises in the membrane, which was originated either from the soluble part of the cell (translocation) or represents a new synthesized form. Particularly, changes of molecular DP IV forms after mitogenic stimulation strongly suggest that special forms/epitopes of this enzyme are directly involved in the process of lymphocyte activation and growth. Importantly, different monoclonal DP IV antibodies partly define different molecular forms of DP IV. Moreover, the pattern of immunostaining and enzymatic staining (Gly-Pro-beta-methoxynaphthylamide) also reveals drastic differences. These data strongly suggest a direct relationship between the expression/recognition of special DP IV epitopes and the contradictory functional effects of monoclonal DP IV antibodies found by us and other groups.

Nitric oxide synthase: expression of the endothelial, Ca2+/calmodulin-dependent isoform in human B and T lymphocytes

Nitric oxide (NO) is a pleiotropic mediator of a variety of cellular processes such as vasorelaxation, neurotransmission, and cytotoxicity. We studied the expression of the human endothelial, Ca2+/calmodulin-dependent NO synthase (NOS) isoform (ecNOS) in highly purified human lymphocytes from peripheral blood and tonsillar T cells. ecNOS mRNA was detected in IgD+ or IgD- B cells, peripheral blood and tonsillar T cells. Upon stimulation, ecNOS mRNA expression decreased in all these lymphocyte subpopulations. Germinal center T cells and follicular dendritic cells did not express ecNOS mRNA either in an unstimulated or in a stimulated state. ecNOS expression by human lymphocytes was further substantiated by its mRNA detection in lymphoid cell lines such as Raji, Daudi, and Jurkat. By the use of a specific monoclonal antibody, ecNOS was shown to be present in T cells from peripheral blood and in various germinal center cells of frozen tonsillar sections. These data are the first to demonstrate the expression of the endothelial ecNOS at mRNA and protein level in human lymphocytes.

Molecular mechanisms of endotoxin activity

Endotoxin (lipopolysaccharide, LPS), a constituent of the outer membrane of the cell wall of gram-negative bacteria, exerts a wide variety of biological effects in humans. This review focuses on the molecular mechanisms underlying these activities and discusses structure-function relationships of the endotoxin molecule, its interaction with humoral and cellular receptors involved in cell activation, and transmembrane and intracellular signal transduction pathways.

Molecular mechanisms of endotoxin activity

Endotoxin (lipopolysaccharide, LPS), a constituent of the outer membrane of the cell wall of gram-negative bacteria, exerts a wide variety of biological effects in humans. This review focuses on the molecular mechanisms underlying these activities and discusses structure-function relationships of the endotoxin molecule, its interaction with humoral and cellular receptors involved in cell activation, and transmembrane and intracellular signal transduction pathways.