Induction of inflammatory mediator release (serotonin and 12-hydroxyeicosatetraenoic acid) from human platelets by Pseudomonas aeruginosa glycolipid

Purified glycolipid from Pseudomonas aeruginosa induced the generation of significant amounts of 12-hydroxyeicosatetraenoic acid (12-HETE) and serotonin release from human platelets. The release of serotonin was first observed 2 min after addition of the glycolipid and increased with time. Significant serotonin release was obtained at glycolipid concentrations above 5 micrograms/ml and increased dose-dependently up to 100% at glycolipid concentrations above 40 micrograms/ml. Glycolipid induced 12-HETE in a time- and dose-dependent manner. 12-HETE formation was first measured after 10 min of incubation and increased with time. Optimal 12-HETE formation was obtained at a glycolipid concentration of 50 micrograms/ml; higher concentrations of glycolipid led to a decrease in 12-HETE formation, indicating a cytotoxic effect. Stimulation of platelets with glycolipid (12-HETE formation and serotonin release) was accompanied by calcium influx, translocation of protein kinase C, activation of guanylylimidodiphosphate binding, and increased GTPase activity in platelet membranes within the same concentration range.

Effects of cefaclor, cefetamet and Ro 40-6890 on inflammatory responses of human granulocytes

The effect of three cephalosporins (cefetamet, cefaclor and Ro 40-6890) upon human granulocytes and their ability to modulate the chemiluminescence response, phagocytose, kill bacteria and generate leukotrienes was studied. In the presence of the cephalosporins there was a significant increase in phagocytosis of Escherichia coli. The bactericidal activity of human granulocytes for several other bacteria was also enhanced. Cefetamet and cefaclor increased the chemiluminescence response of human neutrophils to Pseudomonas aeruginosa and Proteus mirabilis in contrast to Ro 40-68790, which decreased the chemiluminescence response. The cephalosporins decreased the synthesis of leukotrienes from human neutrophils after stimulation with Escherichia coli and Staphylococcus aureus. These data emphasize the immunomodulatory functions of various cephalosporins on cells involved in host defence.

Effects of mucoid and non-mucoid Pseudomonas aeruginosa isolates from cystic fibrosis patients on inflammatory mediator release from human polymorphonuclear granulocytes and rat mast cells

Mucoid Pseudomonas aeruginosa causing chronic bronchopulmonary infection in cystic fibrosis (CF) patients may interfere with host defence mechanisms. We investigated 13 P. aeruginosa strains isolated from sputa of CF patients with regard to the induction or modulation of inflammatory mediator release from human neutrophils (PMN) and rat mast cells. The effects of mucoid as compared to non-mucoid bacteria were studied using a mucoid strain and its non-mucoid revertant. The release of leukotrienes (LT) and histamine in response to the majority of the CF strains was insignificant. However, preincubation of PMN with P. aeruginosa caused a dose-dependent decrease (50-95%) of LTB4 and LTC4 generation and LTB4 metabolism induced by the Ca(2+)-ionophore A23187 or opsonized zymosan (ZX) (P less than 0.001). The mucoid strains caused a three- to 10-fold higher impairment of LTB4 release (P less than 0.05) and a concomitant down-regulation of LTB4 receptors on neutrophils. Inhibitory effects were also obtained for mucoid and non-mucoid bacteria when the phorbol-ester or the Ca(2+)-ionophore induced luminol enhanced chemiluminescence response (P less than 0.001) or the histamine release from rat peritoneal mast cells (P less than 0.01) was studied. The bacteria-cell contact with non-mucoid strains was associated with an increased Ca2+ influx into PMN, whereas mucoid bacteria had no effect. In addition, a protein kinase C-dependent decrease of the C3bi receptor was suppressed by the mucoid--and less effectively--by the non-mucoid strain. The results suggest that the impairment of the phagocytic and inflammatory system may contribute to the pathogenesis and persistence of mucoid P. aeruginosa infection in CF.

Cytokine-induced (interleukins-3, -6 and -8 and tumour necrosis factor-beta) activation and deactivation of human neutrophils

The effect of various cytokines [interleukin-3(IL-3), IL-6, IL-8, tumour necrosis factor-beta (TNF-beta)] on human neutrophils (PMN) was analysed with regard to the generation of leukotrienes and the involvement of guanosine triphosphate (GTP)-binding proteins (G proteins). Incubation of cytochalasin B-pretreated PMN with cytokines alone did not lead to a generation of leukotrienes. However, the cytokines affected the formyl-methionyl-leucyl-phenylalanine-(FMLP)-induced formation of leukotrienes in a time-dependent manner. Preincubation of the cells with the different cytokines for short periods (15 seconds at 37 degrees) enhanced the subsequent FMLP-induced leukotriene generation, whereas preincubation for prolonged times resulted in a reduced formation of leukotrienes. These results correlated with the respective G protein-associated guanosine triphosphatase (GTPase) activities within isolated membrane fractions. The present study indicates a modulation of the FMLP-induced leukotriene formation by diverse cytokines via interaction with the GTP-binding proteins.

Alginate--its role in neutrophil responses and signal transduction towards mucoid Pseudomonas aeruginosa bacteria

Mucoid Pseudomonas aeruginosa bacteria impaired neutrophil functions, e.g. chemiluminescence response, and leukotriene formation to a significantly higher degree as compared to nonmucoid P. aeruginosa bacteria. To study the cell biological requirements for the different cellular response pattern by mucoid and nonmucoid (NM) P. aeruginosa bacteria, further experiments were performed with purified alginate, the mucoid exopolysaccharide of P. aeruginosa (MEP). In this regard the MEP (alginate) significantly reduced the zymosan-induced leukotriene B4 (LTB4) formation (from 40 +/- 7 to 2 +/- 4 ng). The chemiluminescence response induced by NM bacteria was abolished when the bacteria were precoated with the MEP. Mucoid and NM P. aeruginosa bacteria interacted with components of the cellular signal transduction pathway to a different degree. Mucoid bacteria induced a 2-fold enhanced GTPase activity but activated the protein kinase C (PKC) to a lesser degree than NM P. aeruginosa bacteria. Prior exposure of neutrophils to the MEP increased the sodium fluoride (NaF)-induced GTPase activity and guanylylimidodiphosphate binding [Gpp(NH)p] by approximately 60 and 30%, respectively. The phorbol myristic acid-induced PKC activation was inhibited by 30-40% in the presence of the MEP. However, the MEP by itself was inactive in all assay systems. Our results indicate that the MEP represents an important component which modulates neutrophil responses of mucoid as compared to NM P. aeruginosa bacteria, e.g. the chemiluminescence response, LTB4 generation, and the interaction with components (G proteins, PKC) of the signal transduction pathway.

Neomycin induces stimulatory and inhibitory effects on leukotriene generation, guanine triphosphatase activity, and actin polymerization within human neutrophils

The effects of neomycin on human neutrophils (PMN) were studied with respect to the generation of leukotrienes, the involvement of guanine triphosphate binding proteins (G proteins) and the polymerization of actin. Incubation of neutrophils with neomycin induced the generation of low amounts of leukotrienes. Co-incubation of neutrophils with neomycin and the direct G-protein activator sodium fluoride (NaF) resulted in an enhanced leukotriene formation at 0.5 mM neomycin and an inhibition at a concentration of 10 mM. Simultaneous incubation with neomycin and formyl-methionyl-leucyl-phenylalanine (FLMP) did not affect the FMLP-induced leukotriene formation. However, pretreatment of neutrophils with 10 mM neomycin followed by the addition of NaF or FMLP resulted in an enhanced generation of leukotrienes. Crude membrane fractions of PMN incubated with neomycin at different concentrations showed an enhanced (0.5 mM) as well as a reduced (10 mM) guanine triphosphatase activity. Furthermore, incubation of neutrophils with neomycin above a concentration of 0.5 mM led to the depolymerization of actin. The presented results show inhibitory and stimulatory effects of neomycin on various cell functions, which may reflect differences in transmembrane signalling.

Analysis of IgE-binding factors (sCD23) within newborn sera

Factors are discussed as potential diagnostic parameters of atopic disorders. The amounts of sCD23 in sera from newborn children (n = 4,329) were determined by radioimmunoassay with monoclonal antibodies specific for CD23. The sCD23 levels ranged between 0 and 81.5 ng/ml of CD23-specific mAb. Furthermore, the sera of newborns with more than 5 ng/ml (n = 45) were analyzed by SDS/PAGE and subsequent autoradiography using 125I-labeled IgE (PS). These experiments indicate that newborn sera with normal sCD23 amounts contain an IgE-binding activity with a molecular weight of 25 kD; this component was not observed within sera containing elevated amounts (> 5 ng/ml). In addition, a 60-kD IgE-binding component was detected within most of all newborn sera (76.4%). The data show that the IgE-binding pattern of newborn children and the pattern of adult donors are different. Our data suggest that the measurement of quantitative sCD23 amounts combined with the analysis of the molecular weight pattern of the IgE-binding factors might be a helpful diagnostic parameter with regard to IgE-associated diseases.

Influence of Leukotrienes A4 and B4 on the Immunoglobulin Isotype Selection of Normal and Glucocorticoid-Treated Peripheral Blood Mononuclear Cells

We demonstrate that LTA4 (10-100 ng/ml) and LTB4 (10-100 ng/ml) influence the B cell differentiation and isotype switch to a different degree. In contrast to LTB4, LTA4 selectively enhanced the IgG synthesis of B cells and PBMC in the range between 30 and 110% (n = 6, p <0.005). Under the same conditions, both LTs enhance the IL-4-induced CD23 expression of purified B cells by 20-40%. Glucocorticoid (10--7M prednisolone)-treated PBMC, which showed an enhanced Ig(G, A, M, E) synthesis, alter their isotype secretion pattern after LT costimulation. LT costimulation of glucocorticoid-treated cells leads to a suppressed IgG synthesis from 20 to 60% (n = 6, p <0.005). Both LTA4 and LTB4 enhance the IL-4- and glucocorticoid-induced IgE synthesis. Our data thus suggest that LTA4 and LTB4 modulate the immunoglobulin synthesis of PBMC. Both lipid mediators exert different activities on isotype selection.

Analysis of Biological Functions of a 60-kD IgE-Binding Component Derived from Sera of Patients with Atopic Dermatitis

CD23 and its soluble components (sCD23) play an important role in IgE regulation. Sera of patients with atopic dermatitis (AD) were reported to contain an IgE-binding component with a molecular weight of 60 kD. The aim of our study was to analyze the biological functions of the 60-kD component. Sera of patients with AD were fractionated by ammoniumsulfate precipitation, gel filtration, affinity chromatography on IgE-Sepharose or anti-CD23 Sepharose and electroelution from SDS/PAGE. The sCD23-containing preparations were used in cell culture experiments to stimulate peripheral blood lymphocytes of normal donors. Binding studies with IgE peptides demonstrated that CD23 and the 60-kD IgE-binding components bind to the same site. Further experiments were performed to analyze the induced mRNA pattern in the presence of the 60-kD components by polymerase chain reaction (PCR). These data demonstrated that signals for IgE-germ line transcripts and IFN-γ were induced in the presence of the IgE-binding factor preparations from normal peripheral blood lymphocytes whereas there was no signal obtained for IL-2 or IL-4. In addition, it was shown by flow cytometry that the 60-kD component enhanced the expression of adhesion molecules (CD11α, CD18, CD54) whereas the expression of CD23 was reduced.

Effect of antigens from Nippostrongylus brasiliensis and cytokines on the ongoing IgE synthesis in vitro

The modulation of an ongoing IgE-mediated immune response induced by the infection of mice with the nematode Nippostrongylus brasiliensis (N.b.) was investigated in vitro. In previous experiments antigens derived from the homogenate of adult worms (WH) and third stage larvae (LH) were characterized by immunoblotting. Our results demonstrate that only antigens of the WH were recognized by IgE antibodies. The effect of worm antigens and cytokines (IL-2, IL-4, IL-5, IFN gamma) on the IgE and IgG synthesis in different culture systems was studied. The IgG synthesis of B cells was stimulated by WH or WH/cytokines. The IgE production of B cells was enhanced only by WH/cytokines or when T cells were present. Individual antigen fractions (WH 5, 8, 9, 10, 13) increased the IgE production, which was enhanced in the presence of IL-4 2- to 3.5-fold) but had no significant effects on the IgG production.

Differential increase in 12-HETE release and CD29/CD49f expression of platelets from normal donors and from patients with atopic dermatitis by Staphylococcus aureus

The generation of the arachidonic acid-derived inflammatory mediator 12-hydroeicosatetraenoic acid (HETE) and the expression of CD29 as well as CD49f from unstimulated and stimulated platelets has been studied in patients with atopic dermatitis (AD) as well as in healthy volunteers. Heat-killed clinical isolates of Staphylococcus aureus served as stimuli. Unstimulated platelets from patients with AD produced higher amounts of 12-HETE compared to platelets from normal donors. The absolute 12-HETE release from platelets of patients with AD was significantly higher compared to the control group after stimulation with heat-killed S. aureus, whereas the relative increase remained. The expression of CD29 and CD49f on unstimulated platelets of patients with AD was markedly enhanced compared to platelets from normal donors. Stimulation with S. aureus led to similar results as to the CD29 expression on normal and atopic platelets or to a markedly higher expression of CD49f on platelets from normal donors. As compared to platelets from normal donors the CD49f expression on atopic platelets was slightly enhanced by S. aureus. Our data emphasize that platelets may play an important role in the pathogenesis of AD by an increased preactivation and by an enhanced responsiveness to S. aureus which colonizes permanently the skin of patients with AD.

GTPases and Low Molecular Weight G Proteins during Cell-Cell Interaction between Neutrophils and Platelets

The involvement of low molecular weight G proteins (LMWG) was determined during cell-cell interaction between human neutrophils and platelets. α-[32P]-GTP binding revealed an enhanced expression of an 18-kD band and a diminished band at 21 kD derived from platelets after coincubation of both cell types. Coincubation of the cells did not show any effect on the expression of rap2, whereas rapl was enhanced. The subadditive GTPase activity after coincubation of PMN and platelets could be due to some extent to the diminished expression of the ras protein. The presented data suggest an important role of the LMWG during cell-cell interaction between PMN and platelets.

Effects of Staphylococcus aureus cell wall products (teichoic acid, peptidoglycan) and enterotoxin B on immunoglobulin (IgE, IgA, IgG) synthesis and CD23 expression in patients with atopic dermatitis

The influence of staphylococcal cell wall products (teichoic acid, peptidoglycan) and enterotoxin B on peripheral blood lymphocytes (PBL) from patients with atopic dermatitis (AD) was investigated. The parameters studied were spontaneous and interleukin-inducible immunoglobulin (IgA, IgE, IgG) synthesis and CD23 expression. PBL from non-atopic donors served as controls. Teichoic acid and peptidoglycan induced an enhanced synthesis of IgA and IgG in normal donors. However, IgA and IgG synthesis in PBL from patients with AD was significantly suppressed by teichoic acid and enterotoxin B. The incubation of PBL from normal donors with enterotoxin B and interleukin-4 (IL-4) or IL-5 led to a significant suppression of IgA and IgG synthesis. Co-stimulation of PBL with teichoic acid or peptidoglycan and IL-4 led to a pronounced increase in IgE synthesis and CD23 expression in patients with AD. Our data indicate that cell wall products and toxins of staphylococci modulate the cytokine-dependent humoral immunity in patients with AD and may be responsible for allergic skin reactions in AD.

Interleukin 6--a potential mediator of lethal sepsis after major thermal trauma: evidence for increased IL-6 production by peripheral blood mononuclear cells

We studied the plasma levels of the acute phase mediator interleukin 6 (IL-6) in 21 severely burned patients (burn injuries ranging from 24% to 75% total body surface area). The posttraumatic course of the IL-6 plasma levels was closely related to the clinical outcome. The nonseptic survivors as well as survivors with suspected sepsis (n = 14) exhibited maximal amounts of IL-6 (251 +/- 32 pg/mL) during the first 3 days post-burn, which subsequently returned to values within the normal range (days 30 to 50; 26 +/- 8 pg/mL). In the nonsurvivors (n = 7) IL-6 concentrations permanently increased (up to 1,921 +/- 356 pg/mL) until death (days 10 to 19) resulting from sepsis with consecutive multiple organ failure. Peripheral blood mononuclear cells (PBMCs) of patients expressed IL-6-specific mRNA in vivo at high levels in contrast to the PBMCs of healthy donors. In addition, the spontaneous and PHA-induced in vitro production of IL-6 by patients' PBMCs was enhanced compared with healthy controls, whereas no significant differences were obtained with bacterial endotoxin (LPS). The findings suggest that interleukin 6 is a potential mediator of lethal sepsis after major thermal trauma.

[LTB4-metabolism and histamine liberation by granulocytes in the disease pattern of cystic fibrosis (CF)]

We determined the generation and liberation of LTB4 in peripheral granulocytes and the histamine release from basophils in patients suffering from cystic fibrosis (CF, median 17.2 years of age, n = 12). We compared the data with an age matched group of healthy donors (n = 12). All patients suffered from an exacerbation of a chronic pulmonary infection caused by P. aeruginosa. Peripheral granulocytes were stimulated at different days before, during and after antiinfectious treatment with Ca-Ionophore, opsonized zymosan and arachidonic acid. The granulocytes from patients with CF as compared to the control group showed an increased omega-Oxidation of the synthesized LTB4 into 20-COOH- and 20-OH-LTB4 after stimulation with Ca-Ionophore and opsonized zymosan (Ca-Ionophore: ratio of LTB4 versus omega-oxidated products (CF): 0.77 +/- 0.007 mean +/- S.E.M., n = 12, control group: 1.07 +/- 0.1, n = 12, p less than 0.01). Stimulation of the cells with Ca-Ionophore combined with arachidonic acid led to a significantly increased formation of lipoxygenase products in the patient group. No significant differences in the basophil counts were determined between both populations. However, the absolute histamine content per basophil was elevated in the CF group (2.4 +/- 0.3 versus 1.6 +/- 0.2 mean +/- S.E.M., n = 12/12, p less than 0.04). Stimulation of basophils with Ca-Ionophore and anti-IgE leads to a significant higher release of histamine per basophil in CF patients (Ca-Ionophore: 2.6 +/- 0.2 versus 1.3 +/- 0.8 pg/basophil, mean +/- S.E.M., p less than 0.05). These data indicate that basophils in CF may have a greater potential to release mediators. During the antiinfectious treatment a normalization of the altered pattern was observed. Within the CF-groups a strong correlation between the release of LTB4, its metabolites, the histamine release per basophil, the total histamine content and clinical (e.g. pO2 FEV1) and laboratory findings (e.g. IgE and IgG levels, CRP) was established. Our data suggest that the inflammatory process in patients with CF is associated with an alteration of the lipoxygenase pathway and histamine releasability of granulocyte subpopulations which correlates with the clinical signs of inflammation.

Analysis of leukotriene B4 metabolism in human promyelocytic HL-60 cells

We previously reported that human alveolar macrophages rapidly metabolize the chemotactic active lipid mediator leukotriene B4 (LTB4) into the dihydro-LTB4 by reduction of one of the conjugated double bonds. We herein report that human HL-60 cells (a myeloid precursor which can be differentiated into granulocyte- as well as monocyte-like cells by dimethyl sulphoxide or phorbol myristate acetate) express a highly active LTB4 reductase in the undifferentiated state. Differentiation by dimethyl sulphoxide (1.3%) along the granulocyte lineage, as confirmed by light microscopy, conversion of NitroBlue Tetrazolium into formazan, failed to induce a substantial capacity for omega-oxidation of LTB4; this reaction is exclusively found in mature granulocytes. Studies with the cell homogenate of undifferentiated HL-60 cells indicated that the activity of the enzyme depends on the presence of NADPH, Ca2+ and Mg2+, with a pH optimum of 7.5 at 37 degrees C. The enzyme was not released into the supernatant after stimulation of HL-60 cells with phorbol myristate acetate (100 ng) or Ca2+ ionophore (7.5 microM). Subcellular fractionation revealed evidence that the LTB4 reductase is located within the membrane fraction. Purification of the enzyme by gel filtration and gel electrophoresis suggests an apparent molecular mass of 40 kDa.

Effect of interferon-alpha on neutrophil functions

Incubation of neutrophils with interferon-alpha (IFN-alpha) for 5 min and subsequent stimulation with the calcium ionophore A23187 enhanced the production of oxygen radicals, while a suppression was obtained with FMLP-stimulated cells. Similar data were observed for the direct G-protein activator sodium fluoride (NaF). Incubation of the cells with IFN-alpha and subsequent stimulation with FMLP (in the presence of cytochalasin b) reduced the generation of the chemotactic active leukotriene B4 (LTB4). The metabolism of LTB4 was significantly inhibited. IFN-alpha decreased the specific binding sites for LTB4 and increased the number of binding sites for FMLP. The GTPase activity as a parameter for the activation of G-proteins was enhanced by IFN-alpha. Preincubation of the cells with IFN-alpha and subsequent stimulation with NaF increased the GTPase activity synergistically, whereas co-incubation of IFN-alpha with FMLP showed additive effects. Our results clearly demonstrate the modulatory effects of IFN-alpha on granulocyte functions with regard to the receptor-mediated signal transduction.

Roles of human peripheral blood leukocyte protein kinase C and G proteins in inflammatory mediator release by isogenic Escherichia coli strains

The signal transduction pathway (protein kinase C [PKC], calcium influx, and G protein involvement) was studied with isogenic Escherichia coli strains expressing different types of adhesins (MSH+/- MS-Fim+/-, P-MRH+/- P-Fim+/-, and S-MRH+/- S-Fim+/-) or varying only in the expression of E. coli alpha-hemolysin. As target cells, human polymorphonuclear granulocytes (PMN) and a lymphocyte-monocyte-basophil (LMB) cell suspension were used. The alpha-hemolysin-producing (Hly+) strain E. coli K-12(pANN5211) induced calcium influx in a dose-dependent manner in both cell types. No calcium influx was detected after stimulation with the hemolysin-negative (Hly-) E. coli bacteria independent of the type of fimbriae. With Hly+ bacteria, a dose-dependent activation of PKC was observed in both cell types. The Hly- E. coli K-12 induced PKC to a lesser degree, expressing kinetics different from those of E. coli K-12(pANN5211) (Hly+). E. coli MSH+ MS-Fim+ was the most potent activator for PKC. Membrane preparations from leukocytes stimulated with Hly+ E. coli K-12(pANN5211) showed increased binding of [3H]guanylylimidodiphosphate, a nonhydrolyzable GTP analog, and increased GTPase activity compared with leukocytes stimulated with Hly- E. coli K-12. The amounts of GTPase activation and [3H]guanylylimidodiphosphate binding were similar for all Hly- E. coli bacteria in human PMN as well as in human LMB; no activation was obtained for E. coli bacteria without any type of fimbriae. GTP-gamma-S, a nonhydrolyzable GTP analog, inhibited the leukotriene B4 (LTB4) generation from human PMN by Hly- bacteria, unlike E. coli K-12(pANN5211). However, in the presence of NaF, a predominant activator of Gi, LTB4 generation by Hly+ and by Hly- bacteria was significantly enhanced. For LMBs only LTB4 generation by Hly+ bacteria was increased in the presence of GTP-gamma-S. NaF decreased the chemiluminescence induced by all E. coli strains. Our results thus indicate that (i) Hly+ and Hly- bacteria induce the activation of distinct G proteins, e.g., Gi, to different degrees, (ii) LTB4 generation and chemiluminescence response are differently regulated, and (iii) in comparison with PMN, a different signal transduction pathway is activated by E. coli bacteria in LMBs.

Influence of cytokines and cellular interactions on the glucocorticoid-induced Ig (E, G, A, M) synthesis of peripheral blood mononuclear cells

We studied the mechanisms of action leading to the glucocorticoid (GC)-induced synthesis of the immunoglobulins (IgE, G, A, M) by human peripheral blood mononuclear cells (PBMC). It is shown that the enhanced Ig synthesis of GC-stimulated PBMC is dependent on the presence of T cells and monocytes. After stimulation of purified B cells with GC only a slight enhancement of IgM could be detected. Inhibition studies with neutralizing anti-interleukin-4 (IL-4) and anti-IL-6 antibodies revealed that the GC-induced IgE synthesis of PBMC is not dependent on the presence of IL-4 or IL-6. Stimulation of membrane-separated and co-cultured cell fractions revealed that the GC-induced enhancement of IgA and IgM synthesis is mediated by T-cell derived soluble mediators. The GC-induced IgG and IgE synthesis is dependent upon contact of B cells with monocytes. Antibodies against LFA-1 and ICAM-1 are capable to suppress the GC-induced IgE and IgG synthesis of PBMC. Furthermore, the monocyte expression of lymphocyte function antigen-1 (LFA-1), intercellular adhesion molecule-1 (ICAM-1) and HLA-DR is modulated by GC stimulation.

Bacterial toxins induce heat shock proteins in human neutrophils

We studied the influence of different bacterial toxins (alveolysin; toxic shock syndrome toxin 1, TSST-1 and erythrogenic toxin A, ETA) on the expression of heat shock proteins (hsps) in isolated human polymorphonuclear granulocytes (PMNs). As was shown by Western blotting (anti-hsp72) ETA and TSST-1 were potent inducers of hsps at low toxin concentrations (10 ng/ml). Alveolysin led to the expression of hsps at hemolytic concentrations (1 HU; 700 ng/ml) whereas at subhemolytic concentrations (7 ng/ml) no heat shock response was observed. The induction of heat shock proteins was also accompanied by increased mRNA levels for hsp70 as was determined by PCR-analysis.

Regulation of leukotriene B4 generation from human polymorphonuclear granulocytes after stimulation with formyl-methionyl-leucyl phenylalanine: effects of pertussis and cholera toxins

The effects of holotoxins and toxin subunits from Bordetella pertussis and Vibrio cholerae strains on intact and digitonin-permeabilized human polymorphonuclear neutrophils were studied. Our data clearly demonstrate that formyl-methionyl-leucyl-phenylalanine (fMLP)-induced generation of chemotactic active leukotriene B4 was inhibited by both holotoxins as well as by their isolated enzymatic A protomers. In contrast, the respective binding components (B oligomers) did not affect leukotriene formation. Priming of digitonin-permeabilized neutrophils with either guanylylimidodiphosphate or inositol trisphosphate increased subsequent stimulation with fMLP. In contrast, diacylglycerol decreased fMLP-induced leukotriene B4 formation, but inositol trisphosphate and diacylglycerol had no effect on inhibition mediated by the toxins. In addition, pertussis and cholera toxins reduced the specific binding of [3H]fMLP. Scatchard plot analysis revealed that the observed decrease of peptide binding was due to a reduced number of receptor sites. The fMLP-stimulated [3H]guanylylimidodiphosphate binding and GTPase activity used as parameters for the activation of G proteins were decreased in parallel. These results suggest altered chemotactic receptor numbers and G-protein functions responsible for the toxin-dependent suppression of fMLP-mediated response for neutrophils.

Metabolism of leukotriene B4 via reduction into dihydro-leukotriene B4 in human monocytes, alveolar macrophages, and U-937 cells

The biological effects of leukotriene B4 (LTB4) within the microenvironment are controlled by rapid inactivation. In this regard human granulocytes convert LTB4 into omega-oxidated products (20-OH-LTB4 and 20-COOH-LTB4); moreover, we recently described the formation of unpolar metabolites of LTB4 in human tonsillar and lung macrophages. By means of high performance liquid chromatography (HPLC) we identified the main metabolite of LTB4 as dihydro-LTB4 (5,12-dihydroxyeicosatrienoic acid). Studies on a lymphocyte (74-78%), monocyte (19-22%), and basophil (less than 4%) containing cell fraction isolated from peripheral blood as well as peripheral monocytes purified by elutriation centrifugation revealed evidence that these cells metabolize LTB4 to a very low degree if incubated immediately after isolation. However, after culture for 24-72 h these cells showed a strongly increased capacity to metabolize LTB4. The pattern of metabolites in this cell fraction was identical to bronchoalveolar macrophages (purity greater than 95%). Similarly, the LTB4-reductase was expressed in differentiated human monocytic U-937 cells almost 5-7 h after the addition of dimethylsulfoxide (1.3%) or phorbol-myristate-acetate (16 nM). The expression of this pathway was blocked in the presence of cycloheximide (10 micrograms/ml) whereas actinomycin (3.8 micrograms/ml) had no effects. Dihydro-LTB4 was further metabolized by granulocytes probably via omega-oxidation; therefore, several metabolites could be detected by radioactive high performance liquid chromatography (HPLC) after incubation of bronchoalveolar cells consisting of macrophages and granulocytes with 3H-LTB4. Our data provide evidence for a unique role of macrophages to control the level of LTB4 by generation as well as metabolism into dihydro-LTB4.

Serum CD14 levels in polytraumatized and severely burned patients

Recently it has been demonstrated that the CD14 molecule which is expressed on monocytes and macrophages serves as a receptor for lipopolysaccharide (LPS) bound to LPS-binding protein (LBP) and thus mediates LPS-induced tumour necrosis factor (TNF) production. Here we report that CD14 is found as a soluble (s) molecule in serum. In healthy volunteers sCD14 levels (mean +/- s.e.m.) were 3.7 +/- 0.05 micrograms/ml (n = 30, 25-50 years of age) as determined by ELISA (detection limit 20 ng/ml serum) using two monoclonal antibodies in a sandwich technique. In polytraumatized patients (n = 16) significantly decreased levels (1.7 +/- 0.3) were detected immediately after the trauma, which increased to 4.9 +/- 0.3 micrograms/ml within the first 6 days post trauma. sCD14 remained elevated during the first 14 days post trauma in patients with the most severe injuries (injury severity score greater than 45 points), whereas a return to normal levels was observed in patients with an injury score of less than 45 points. In addition, the levels of the high-density lipoproteins that partially inactivate free endotoxin are significantly decreased post trauma. No correlation between parameters of inflammation (C3a and neopterin levels, leucocyte counts, amount of band cells), liver function and sCD14 levels was established. Comparable to polytraumatized patients, increased sCD14 serum levels were observed in five patients with burn trauma (burned area greater than 35%) within the second week post trauma when clinical signs of septicaemia were evident.