Siglec-9 modulated IL-4 responses in the macrophage cell line RAW264

Siglecs, an immunoglobulin-like lectin family that recognizes the sialic acid moiety, regulate various aspects of immune responses. In the present study, we investigated the effects of Siglecs on the macrophage cell line RAW264, which was stimulated with interleukin-4 (IL-4). The induction of arginase-1 (Arg1) by IL-4 was stronger in Siglec-9-expressing cells than in mock cells. Mutations in the cytoplasmic tyrosine-based inhibitory motifs in Siglec-9 markedly reduced the expression of Arg1. The phosphorylation of Akt by IL-4 and extracellular signal-regulated kinase (ERK) without IL-4 was stronger in Siglec-9-expressing cells, indicating the enhanced activation of the phosphatidylinositol 3 kinase (PI-3K) and mitogen-activated protein kinase kinase (MEK)/ERK pathways, respectively. The enhanced expression of Arg1 was inhibited by MEK inhibitors, but not by PI-3K inhibitor. These results indicate that Siglec-9 affects several different signaling pathways in IL-4-stimulated macrophages, which resulted in enhanced induction of Arg1 in Siglec-9-expressing RAW264 cells.     

Immunochemical evidence for a novel pertussis toxin substrate in human neutrophils

Pertussis toxin catalyzes incorporation of 20.2 pmol of ADP-ribose/mg of protein into approximately 40-kDa protein(s) in human neutrophil membranes compared with 14.1 pmol/mg in bovine brain membranes. Based on these measurements we estimate that pertussis toxin substrate(s) should represent at least 0.085% of total membrane protein in neutrophils. Both brain and neutrophil membranes show high concentrations (0.34 versus 0.16% of total membrane protein, respectively) of the common beta subunit of guanine nucleotide binding proteins. Affinity purified antibodies specific for Go-alpha fail to detect any protein in immunoblots of neutrophil membranes (150 micrograms) under conditions where as little as 10 ng of purified Go-alpha is detectable, and Go-alpha is readily detected in brain membranes (100 micrograms). An antiserum against transducin that cross-reacts strongly with Gi-alpha, detects as little as 5 ng of purified Gi-alpha and readily detects Gi-alpha in brain membranes, but in neutrophil membranes, the antiserum detects an approximately 40-kDa band that corresponds to less than 10% of the expected amount of pertussis toxin substrate(s). The results show that human neutrophil membranes contain relatively large amounts of pertussis toxin substrate(s), but that the predominant pertussis toxin substrate is immunochemically distinct from previously identified substrates, transducin, Gi, and Go.     

Subcellular localization and quantitation of the major neutrophil pertussis toxin substrate, Gn

The subcellular distribution of G protein subunits in the neutrophil was examined. Cells were nitrogen cavitated and subcellular organelles fractionated on discontinuous sucrose gradients. The presence of GTP-binding regulatory protein (G protein) alpha and beta/gamma subunits in each organelle was determined using three methods of analysis: specific binding of guanine nucleotide, ADP ribosylation by pertussis toxin, and immunoblot analysis with subunit-specific G protein antibodies. Both plasma membrane and cytosolic G protein components were detected. In contrast, neither the specific nor the azurophilic granules contained detectable G protein. Based on the ability of exogenous G protein beta/gamma subunits to increase the ADP ribosylation of the cytosolic form of G protein and upon the hydrodynamic behavior of the cytosolic protein, it is likely that this represents an uncomplexed G protein alpha subunit. Proteolytic mapping with Staphylococcus aureus V8 protease suggests the soluble alpha subunit is from Gn, the major pertussis toxin substrate of human neutrophils. Using quantitative analysis, the levels of the 40-kD G protein alpha subunit and of the 35/36-kD beta subunit in the neutrophil membrane were determined.     

Melanocortin receptor signaling in RAW264.7 macrophage cell line

Melanocortin peptides modulate cytokine release and adhesion molecule expression. Here we have investigated the early cell-signaling pathway responsible for the induction of interleukin-10 (IL-10) in RAW264.7 cells. Cell incubation with ACTH(1-39) or MTII (melanotan II) did not alter ERK1/2 and JNK phosphorylation, while p38 phosphorylation and intracellular cAMP accumulation occurred within minutes. ACTH(1-39) and MTII provoked a time-dependent accumulation of IL-10 that was abrogated by the PKA inhibitor H-89 and only partially blocked by the p38 MAPK inhibitor SB203580. Thus, in RAW264.7 cells, IL-10 induction by the melanocortins is via the PKA pathway, and this mechanism could contribute to their anti-inflammatory profile.     

Immunochemical comparison of pertussis toxin substrates in brain and peripheral tissues

The tissue distribution of pertussis toxin-sensitive GTP-binding proteins was examined using specific antibodies raised against the purified -subunit of G₀ from bovine brain or against synthetic peptides predicted from cDNAs for distinct G_i subtypes. GTP-binding proteins were partially purified from membrane fractions prepared from rabbit tissues including brain, heart, liver, lung, erythrocytes and neutrophilis. Brain contained both G₀ and G₁. G_il was also found to be abundant in heart. All peripheral tissues contained tissues contained readily detectable amounts of G₁₂, whereas only barely detectable amounts of G_i2 were found in brain. G_i3 was found to be prominent in erythorocytes and exists as a minor component of G proteins in neutrophils and liver. Thus, G_i2 appears to be widely disseminated in peripheral rabbit tissues, while other pertussis toxin substrates are more limited in their distribution.     

Immunomodulatory effects of specific bacterial components of Lactobacillus plantarum KFCC11389P on the murine macrophage cell line RAW 264·7

Aims:  The objective of this study was to investigate the ability of specific bacterial components of Lactobacillus plantarum KFCC11389P to induce anti-inflammatory mediators in cell cultures of the murine macrophage cell line, RAW 264·7.
Methods and Results:  The RAW 264·7 cells were stimulated with viable bacterial cells (VC), heat-killed (HK) cells, cell walls (CW) or ultrafiltrates of metabolic products (UF). An increase in the levels of tumour necrosis factor (TNF)-α was observed in VC, HK and CW, but this effect was much lower in UF. VC stimulated higher levels of interleukin (IL)-6 releases as well as nitric oxide production than HK. In contrast, UF and its separated molecule, fraction 4, were much strong IL-10 inducers. Fraction 4 (8·1 kDa), especially, inhibited the production of pro-inflammatory cytokines, IL-6 (89% decrease) and TNF-α (55% decrease), in lipopolysaccharide (LPS)-stimulated murine macrophages.
Conclusions:  The results of this study indicate that metabolic products of Lact. plantarum KFCC11389P could influence the immune-modulating activity via IL-10, and pretreatment with this specific molecule could inhibit LPS-induced release of IL-6 and TNF-α.
Significance and Impact of the Study:  Our findings suggest that the specific molecules of Lact. plantarum KFCC11389P may be useful for the treatment of acute inflammatory responses such as Crohn's disease or ulcerative colitis.     

Mechanisms of activation of the RAW264.7 macrophage cell line by transfected mammalian DNA

Bacterial DNA can stimulate the production of cytokines and nitric oxide (NO), while mammalian DNA can block these responses. If mammalian DNA is transfected into macrophages, however, it can stimulate NO production, without inducing IL-12. To define further this activity, signaling pathways induced by transfected calf thymus (CT) DNA were studied. Using RAW264.7 cells as a model, CT DNA in the transfection agent FuGENE 6 activated cells through the NF-kappaB and MAPKs pathways, similar to bacterial DNA and LPS. The role of these pathways was further investigated using specific inhibitors, with studies indicating that NO production is blocked by inhibitors of NF-kappaB and p38 but not other MAPKs. These data indicate that the immune activity of DNA is influenced by context or intracellular location and that, when transfected into cells, mammalian DNA can activate cells through signaling pathways similar to those of bacterial DNA.     

Purification and characterization of a GTP-binding protein serving as pertussis toxin substrate in starfish oocytes

In response to a meiosis-inducing hormone, 1-methyladenine (1-MA), starfish oocytes undergo reinitiation of meiosis with germinal vesicle breakdown. The 1-MA-initiated signal is, however, inhibited by prior microinjection of pertussis toxin into the oocytes (Shilling, F., Chiba, K., Hoshi, M., Kishimoto, T., and Jaffe, L.A. (1989) Dev. Biol. 133, 605-608), suggesting that a pertussis-toxin-sensitive guanine-nucleotide-binding protein (G protein) is involved in the 1-MA-induced signal transduction. Based on these findings, we purified a G protein serving as the substrate of pertussis toxin from the plasma membranes of starfish oocytes. The purified G protein had an alpha beta gamma-trimeric structure consisting of 39-kDa alpha, 37-kDa beta, and 8-kDa gamma subunits. The 39-kDa alpha subunit contained a site for ADP-ribosylation catalyzed by pertussis toxin. The alpha subunit was also recognized by antibodies specific for a common GTP-binding site of many mammalian alpha subunits or a carboxy-terminal ADP-ribosylation site of mammalian inhibitory G-alpha. An antibody raised against mammalian 36-/35-kDa beta subunits strongly reacted with the 37-kDa beta subunit of starfish G protein. The purified starfish G protein had a GTP-binding activity with a high affinity and displayed a low GTPase activity. The activity of the G protein serving as the substrate for pertussis-toxin-catalyzed ADP-ribosylation was inhibited by its association with a non-hydrolyzable GTP analogue. Thus, the starfish G protein appeared to be similar to mammalian G proteins at least in terms of its structure and properties of nucleotide binding and the pertussis toxin substrate. A possible role of the starfish G protein is also discussed in the signal transduction between 1-MA receptors and reinitiation of meiosis with germinal vesicle breakdown.     

Opisthorchis viverrini antigen induces the expression of Toll-like receptor 2 in macrophage RAW cell line

Opisthorchis viverrini infection induces inflammation in and around the bile duct, leading to cholangiocarcinoma in humans. To examine the mechanism of O. viverrini-induced inflammatory response, we assessed the expression of Toll-like receptors (TLRs) in RAW 264.7 macrophage cell line treated with an extract of O. viverrini antigen. Flow cytometry and immunocytochemistry showed that O. viverrini antigen induced the expression of TLR2 but not TLR4. Western blotting and immunocytochemistry revealed that nuclear factor-kappaB (NF-kappaB), inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) were expressed in RAW 264.7 cells treated with O. viverrini antigen in a dose-dependent manner. These results suggest that O. viverrini induces inflammatory response through TLR2-mediated pathway leading to NF-kappaB-mediated expression of iNOS and COX-2.     

Characterization of casein kinase II from a virally transformed macrophage-like cell line, RAW264

Casein kinase II from a virally-transformed macrophage cell line (RAW264) was purified by a sequential DEAE, Procion Red, phosvitin-Sepharose and heparin-Sepharose chromatography. With [tau-32P]GTP as a phosphate donor and casein as a substrate, the kinase was stimulated by polyamines and inhibited by heparin. The purified kinase had a specific activity of 1137 nmol/min/mg protein and exhibited three major protein bands of 40 K, 35 K, and 25 K. Under non-denaturing conditions in 50 mM Tris-50 mM NaCl the enzyme was eluted as a single peak with molecular weight of 110 K. Incubation of kinase in the presence of [tau-32P]GTP and Mg2+ resulted in phosphorylation of the 25 K protein band of the enzyme. In the presence of [tau-32P]GTP and Mg2+ the kinase was able to phosphorylate 55 K protein band in purified ornithine decarboxylase preparation from RAW264 cells and the rat-type II regulatory subunit of the cyclic AMP-dependent protein kinase.     

Structural characterization of pertussis toxin A subunit

The relationship between the structure of the A subunit of pertussis toxin and its function was analyzed. Limited tryptic digestion of the A subunit converted the protein to two stable fragments (Mr = 20,000 and 18,000). Antibodies raised to synthetic peptides homologous to regions in the A subunit were used to map these fragments. Both fragments were shown to contain the NH2-terminal portion but not the COOH-terminal portion of the A subunit. While these fragments exhibited NAD glycohydrolase activity, they were unable to reassociate with the B oligomer of the toxin. Thus the COOH-terminal portion of the A subunit does not contain the residues which are required for the NAD glycohydrolase activity of the toxin. However, this region of the molecule may be important for maintaining the oligomeric structure of the toxin. These results suggest that the A subunit of pertussis toxin is similar in structure to the A subunit of cholera toxin. In addition, antibodies raised to a synthetic peptide identical to residues 6-17 of the A subunit of pertussis toxin will bind to the A subunit of cholera toxin.     

Uptake of histamine by mouse peritoneal macrophages and a macrophage cell line,RAW264.7

We have previously demonstrated that dietary histamine is accumulated in the spleens of L-histidine decarboxylase (HDC)-deficient mice, which lack endogenous histamine synthesis. To characterize the clearance system for dietary histamine in mice, we investigated the cell type and mechanism responsible for histamine uptake in the spleens of HDC-deficient mice. Immunohistochemical analyses using an antihistamine antibody indicated that a portion of the CD14⁺ cells in the spleen is involved in histamine storage. Peritoneal macrophages obtained from Balb/c mice and a mouse macrophage cell line, RAW264.7, had potential for histamine uptake, which was characterized by a low affinity and high capacity for histamine. The histamine uptake by RAW264.7 cells was observed at physiological temperature and was potently inhibited by pyrilamine, chlorpromazine, quinidine, and chloroquine, moderately inhibited by N-methylhistamine, dopamine, and serotonin, and not affected by tetraethylammonium and 1-methyl-4-phenylpyridinium. Intracellular histamine was not metabolized in RAW264.7 cells and was released at physiological temperature in the absence of extracellular histamine. These results suggest that histamine uptake by macrophages may be involved in the clearance of histamine in the local histamine-enriched environment. cation transporter; chlorpromazine; pyrilamine; quinidine     

Production of cell mass and pertussis toxin by Bordetella pertussis.

The cultivation of Bordetella pertussis affects production of pertussis toxin and biomass. Comparison of batch mode, chemostat operation and pHstat-turbidostatic control showed that productivities for the continuous process were greater than that for the batch operation. Continuous operation in balanced growth at the maximum specific growth rate, provided by the pHstat, resulted in the maximum specific production rate. Because of the strong association of pertussis toxin synthesis and cell growth, the concentration of toxin in the effluent of the continuous processes was greater than the maximum obtained in the batch bioprocess. An expanded Luedeking-Piret model of product formation kinetics fits the observed chemostat data and demonstrates that the production of pertussis toxin from the culture of B. pertussis is predominantly growth associated.     

Nitration of PPARgamma inhibits ligand-dependent translocation into the nucleus in a macrophage-like cell line,RAW 264

Baeyer-Villiger monooxygenases (BVMOs) form a distinct class of flavoproteins that catalyze the insertion of an oxygen atom in a C-C bond using dioxygen and NAD(P)H. Using newly characterized BVMO sequences, we have uncovered a BVMO-identifying sequence motif: FXGXXXHXXXW(P/D). Studies with site-directed mutants of 4-hydroxyacetophenone monooxygenase from Pseudomonas fluorescens ACB suggest that this fingerprint sequence is critically involved in catalysis. Further sequence analysis showed that the BVMOs belong to a novel superfamily that comprises three known classes of FAD-dependent monooxygenases: the so-called flavin-containing monooxygenases (FMOs), the N-hydroxylating monooxygenases (NMOs), and the BVMOs. Interestingly, FMOs contain an almost identical sequence motif when compared to the BVMO sequences: FXGXXXHXXX(Y/F). Using these novel amino acid sequence fingerprints, BVMOs and FMOs can be readily identified in the protein sequence databank.     

Myo-inositol restores the inflammation-induced down-regulation of taurine transport by the murine macrophage cell line,RAW 264.7

The role of myo-inositol in the regulation of taurine transport in activated murine macrophage cell line, RAW 264.7, was studied. Challenge of RAW 264.7 murine macrophages for 24 hr with phorbol ester 12-myristate 13-acetate (PMA) (10 ng/ml), a PKC activator, resulted in a 62% decrease in taurine transport activity. Among the various monosaccharides (1 mM) tested in the presence of PMA, myo-inositol was most effective in restoring the PMA-induced down-regulation of taurine transport in murine macrophages (82% increase compared to the value for cells treated with PMA Alone, p < 0.01). The protective role of myo-inositol against stress-induced down-regulation of taurine transport by macrophages was further investigated in conditions mimicking bacterial infection, inflammation, and immune-suppressed circumstances. A challenge of murine macrophages with lipopolysaccharide (LPS) (0.1 and 10 microg/ml) resulted in a 60% decrease in taurine transport activity compared to the value for untreated control cells (p < 0.01). When cells were co-treated with myo-inositol (100 nM approximately 10 mM) in the presence of LPS for 24 hrs, taurine transport activity increased in a dose-dependent manner compared to the value for cells treated with LPS only. Taurine transport activity in cells treated with LPS (10 microg/ml) plus interferon-gamma (IFN-gamma) (150 unit/ml) for 24 hrs was 13% of the value for untreated control cells (p < 0.01). Again, this inflammation-induced down-regulation of taurine transport activity was completely antagonized with co-administration of 100 nM or higher levels of myo-inositol in the culture medium. Similarly, myo-inositol effectively restored the taurine transport activity suppressed by cyclosporin A (0.5 and 50 nM) in murine macrophages (p < 0.01). From these results, myo-inositol appears to be a common accelerator of taurine transport by murine macrophages in diverse conditions of down-regulated taurine transport.