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R. Van Furth - One of the best experts on this subject based on the ideXlab platform.
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Arachidonic acid, but not its metabolites, is essential for FcγR‐stimulated Intracellular Killing of Staphylococcus aureus by human monocytes
Immunology, 1999Co-Authors: Limin Zheng, R. Van Furth, M. T. Van Den Barselaar, T. P. L. Zomerdijk, M. F. Geertsma, P. H. NibberingAbstract:Since arachidonic acid (AA) production by phospholipase A2 (PLA2) is essential for the Fcγ receptor (FcγR)-mediated respiratory burst and phagocytosis of opsonized erythrocytes by monocytes and macrophages, we focused in this study on the role of AA and its metabolites in the FcγR-stimulated Intracellular Killing of Staphylococcus aureus by human monocytes. The results revealed that the PLA2 inhibitors, but not inhibitors of cyclo-oxygenase and lipoxygenase, markedly suppressed the FcγR-mediated Killing process. The production of O−2 by monocytes upon FcγR cross-linking was inhibited by 4-bromophenacyl bromide in a dose-dependent fashion, indicating that inhibition of PLA2 activity impairs the oxygen-dependent bactericidal mechanisms of monocytes, which could be partially restored by addition of exogenous AA and docosahexaenoic acid, but not myristic acid. These polyunsaturated fatty acids, but not myristic acid, stimulated the Intracellular Killing of S. aureus by monocytes, although not as effectively as FcγR cross-linking. Furthermore, FcγR cross-linking stimulated the release of AA from monocytes. Studies with selective inhibitors revealed that the FcγR-mediated activation of PLA2 is dependent on Ca2+ and tyrosine kinase activity. Together these results indicate a key role for PLA2/AA, but not its major metabolites, in mediating the FcγR-stimulated Intracellular Killing of S. aureus by monocytes.
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Protein tyrosine kinase activity is essential for Fc gamma receptor-mediated Intracellular Killing of Staphylococcus aureus by human monocytes.
Infection and immunity, 1994Co-Authors: Limin Zheng, P. H. Nibbering, T. P. L. Zomerdijk, R. Van FurthAbstract:Our previous study revealed that the Intracellular Killing of Staphylococcus aureus by human monocytes after cross-linking Fc gamma receptor I (Fc gamma RI) or Fc gamma RII is a phospholipase C (PLC)-dependent process. The aim of the present study was to investigate whether protein tyrosine kinase (PTK) activity plays a role in the Fc gamma R-mediated Intracellular Killing of bacteria and activation of PLC in these cells. The results showed that phagocytosis of bacteria by monocytes was not affected by the PTK inhibitors genistein and tyrphostin-47. The Intracellular Killing of S. aureus by monocytes after cross-linking Fc gamma RII or Fc gamma RII with anti-Fc gamma R monoclonal antibody and a bridging antibody or with human immunoglobulin G (IgG) was inhibited by these compounds in a dose-dependent fashion. The production of O2- by monocytes after stimulation with IgG or IgG-opsonized S. aureus was almost completely blocked by the PTK inhibitor. These results indicate that inhibition of PTK impairs the oxygen-dependent bactericidal mechanisms of monocytes. Genistein and tyrphostin-47, which do not affect the enzymatic activity of purified PLC, prevented activation of PLC after cross-linking Fc gamma RI or Fc gamma RII, measured as an increase in the Intracellular inositol 1,4,5-trisphosphate concentration. Cross-linking Fc gamma RI or Fc gamma RII induced rapid tyrosine phosphorylation of several proteins in monocytes, one of which was identified as PLC-gamma 1, and the phosphorylation could be completely blocked by PTK inhibitors, leading to the conclusion that activation of PLC after cross-linking Fc gamma R in monocytes is regulated by PTK activity. Together, these results demonstrate that PTK activity is essential for the activation of PLC which is involved in the Fc gamma R-mediated Intracellular Killing of S. aureus by human monocytes.
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Differences in the Rate of Intracellular Killing of Catalase- Negative and Catalase-Positive Listeria monocytogenes by Normal and Interferon-Gamma-Activated Macrophages
Scandinavian journal of immunology, 1993Co-Authors: J. T. Van Dissel, J. J. M. Stikkelbroeck, R. Van FurthAbstract:Intracellular Killing of catalase-positive bacteria by murine resident macrophages requires the presence of extracellular serum, whereas Killing of catalase-negative bacteria can occur in the absence of serum. To find out whether the Intracellular Killing of bacteria by rIFN-gamma-activated macrophages also requires serum stimulation, we investigated the handling of ingested catalase-negative and -positive Listeria monocytogenes by peritoneal macrophages of normal Swiss mice and mice injected i.p. with 1 x 10(4) U rIFN-gamma 18 h earlier. In the absence of extracellular serum, rIFN-gamma-activated macrophages killed ingested catalase-negative Listeria more efficiently (P < 0.01) than normal resident macrophages. Maximal Killing of catalase-negative bacteria by rIFN-gamma-activated macrophages required an extracellular serum concentration of only 1.0 to 2.5% compared with the 10% needed by normal macrophages. No differences were observed in the rates of Intracellular Killing of catalase-positive Listeria by rIFN-gamma-activated and normal resident macrophages: both populations of macrophages required 10% extracellular serum for maximal Killing of these bacteria, and Killing was minimal in the absence of serum. The rIFN-gamma-activated macrophages displayed enhanced O2-consumption after stimulation with phorbol myristate acetate and heat-killed Listeria compared with macrophages from normal mice. These findings indicate that, under suboptimal stimulation by extracellular serum, rIFN-gamma enhances the Intracellular Killing of catalase-negative Listeria which lack endogenous catalase acting as a scavenger of reactive oxygen intermediates. The mechanism underlying the enhancement is probably the amplification of the respiratory burst by IFN-gamma.
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Cytosolic free calcium is essential for immunoglobulin G-stimulated Intracellular Killing of Staphylococcus aureus by human monocytes.
Infection and immunity, 1992Co-Authors: Limin Zheng, P. H. Nibbering, R. Van FurthAbstract:Earlier studies have shown that the Intracellular Killing of Staphylococcus aureus by human monocytes requires continuous stimulation by serum factors, e.g., immunoglobulin G (IgG). In the present study, we demonstrate that IgG, at concentrations that stimulate the Intracellular Killing of S. aureus, induces a transient increase in the Intracellular free calcium concentration ([Ca2+]i) in monocytes. The Ca2+ ionophores A23187 and ionomycin stimulate the Killing process as efficiently as IgG does and initiate O2- production in resting monocytes but not in monocytes containing bacteria. The Ca2+ ionophore-stimulated Killing process was markedly inhibited by the NADPH oxidase inhibitor diphenyleneiodonium bisulfate, which indicates that these ionophores stimulate oxygen-dependent bactericidal mechanisms. Reduction of the [Ca2+]i to values below 1 nM, obtained by loading monocytes with MAPT/AM (1,2-bis-5-methyl-aminophenoxylethane-N,N,N',N'-tetraacetoxymet hyl acetate) in the absence of extracellular Ca2+, rendered the cells unresponsive to IgG or Ca2+ ionophore stimulation of the Intracellular Killing of S. aureus, but the response could be restored by reincubating these cells in the presence of extracellular Ca2+. It is concluded that cytosolic free Ca2+ is essential for the IgG-stimulated Intracellular Killing of S. aureus by human monocytes.
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Pertussis toxin partially inhibits phagocytosis of immunoglobulin G-opsonized Staphylococcus aureus by human granulocytes but does not affect Intracellular Killing.
Infection and immunity, 1992Co-Authors: Pieter S. Hiemstra, A. Annema, E F Schippers, R. Van FurthAbstract:Abstract The aim of the present study was to determine whether pertussis toxin (PT)-sensitive GTP-binding proteins (G proteins) are involved in the signal transduction pathway(s) used for phagocytosis and Intracellular Killing of bacteria by human granulocytes. Treatment of granulocytes with PT resulted in decreased phagocytosis of immunoglobulin G (IgG)-opsonized Staphylococcus aureus but did not affect subsequent Intracellular Killing of these bacteria. PT also caused a decrease in the extracellular release of superoxide anion (O2-) and hydrogen peroxide (H2O2) by granulocytes in response to S. aureus opsonized by IgG. However, neither the phagocytosis nor the Intracellular Killing of S. aureus opsonized by fresh serum was affected by PT, and the release of O2- was partially inhibited. The release of O2- in response to serum-treated zymosan, opsonized mainly by complement components, was also only partially inhibited by PT. It is therefore possible that PT inhibits responses mediated through complement receptors to a lesser extent than those mediated via Fc gamma receptors. The results of this study indicate that PT-sensitive G proteins are involved in the signal transduction pathways that mediate the phagocytosis of IgG-opsonized bacteria and the accompanying respiratory burst.
Wanessa Cristina Lima - One of the best experts on this subject based on the ideXlab platform.
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LrrkA, a kinase with leucine-rich repeats, links folate sensing with Kil2 activity and Intracellular Killing.
Cellular microbiology, 2019Co-Authors: Romain Bodinier, Jade Leiba, Ayman Sabra, Anna Marchetti, Tania Jauslin, Otmane Lamrabet, Cyril Guilhen, Yumi Iwade, Takefumi Kawata, Wanessa Cristina LimaAbstract:Phagocytic cells ingest bacteria by phagocytosis and kill them efficiently inside phagolysosomes. The molecular mechanisms involved in Intracellular Killing and their regulation are complex and still incompletely understood. Dictyostelium discoideum has been used as a model to discover and to study new gene products involved in Intracellular Killing of ingested bacteria. In this study, we performed random mutagenesis of Dictyostelium cells and isolated a mutant defective for growth on bacteria. This mutant is characterized by the genetic inactivation of the lrrkA gene, which encodes a protein with a kinase domain and leucine-rich repeats. LrrkA knockout (KO) cells kill ingested Klebsiella pneumoniae bacteria inefficiently. This defect is not additive to the Killing defect observed in kil2 KO cells, suggesting that the function of Kil2 is partially controlled by LrrkA. Indeed, lrrkA KO cells exhibit a phenotype similar to that of kil2 KO cells: Intraphagosomal proteolysis is inefficient, and both intraphagosomal Killing and proteolysis are restored upon exogenous supplementation with magnesium ions. Bacterially secreted folate stimulates Intracellular Killing in Dictyostelium cells, but this stimulation is lost in cells with genetic inactivation of kil2, lrrkA, or far1. Together, these results indicate that the stimulation of Intracellular Killing by folate involves Far1 (the cell surface receptor for folate), LrrkA, and Kil2. This study is the first identification of a signalling pathway regulating intraphagosomal bacterial Killing in Dictyostelium cells.
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Vps13F links bacterial recognition and Intracellular Killing in Dictyostelium.
Cellular microbiology, 2017Co-Authors: Jade Leiba, Romain Bodinier, Ayman Sabra, Anna Marchetti, Wanessa Cristina Lima, Astrid Melotti, Jackie Perrin, Frédéric Burdet, Marco Pagni, Thierry SoldatiAbstract:Bacterial sensing, ingestion, and Killing by phagocytic cells are essential processes to protect the human body from infectious microorganisms. The cellular mechanisms involved in Intracellular Killing, their relative importance, and their specificity towards different bacteria are however poorly defined. In this study, we used Dictyostelium discoideum, a phagocytic cell model amenable to genetic analysis, to identify new gene products involved in Intracellular Killing. A random genetic screen led us to identify the role of Vps13F in Intracellular Killing of Klebsiella pneumoniae. Vps13F knock-out (KO) cells exhibited a delayed Intracellular Killing of K. pneumoniae, although the general organization of the phagocytic and endocytic pathway appeared largely unaffected. Transcriptomic analysis revealed that vps13F KO cells may be functionally similar to previously characterized fspA KO cells, shown to be defective in folate sensing. Indeed, vps13F KO cells showed a decreased chemokinetic response to various stimulants, suggesting a direct or indirect role of Vps13F in Intracellular signaling. Overstimulation with excess folate restored efficient Killing in vps13F KO cells. Finally, genetic inactivation of Far1, the folate receptor, resulted in inefficient Intracellular Killing of K. pneumoniae. Together, these observations show that stimulation of Dictyostelium by bacterial folate is necessary for rapid Intracellular Killing of K. pneumoniae.
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Intracellular Killing of bacteria: is Dictyostelium a model macrophage or an alien?
Cellular microbiology, 2014Co-Authors: Pierre Cosson, Wanessa Cristina LimaAbstract:Predation of bacteria by phagocytic cells was first developed during evolution by environmental amoebae. Many of the core mechanisms used by amoebae to sense, ingest and kill bacteria have also been conserved in specialized phagocytic cells in mammalian organisms. Here we focus on recent results revealing how Dictyostelium discoideum senses and kills non-pathogenic bacteria. In this model, genetic analysis of Intracellular Killing of bacteria has revealed a surprisingly complex array of specialized mechanisms. These results raise new questions on these processes, and challenge current models based largely on studies in mammalian phagocytes. In addition, recent studies suggest one additional level on complexity by revealing how Dictyostelium recognizes specifically various bacterial species and strains, and adapts its metabolism to process them. It remains to be seen to what extent mechanisms uncovered in Dictyostelium are also used in mammalian phagocytic cells.
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Phg1/TM9 proteins control Intracellular Killing of bacteria by determining cellular levels of the Kil1 sulfotransferase in Dictyostelium.
PloS one, 2013Co-Authors: Marion Le Coadic, Anna Marchetti, Wanessa Cristina Lima, Romain Bruno Froquet, Marco Dias, Pierre CossonAbstract:Dictyostelium discoideum has largely been used to study phagocytosis and Intracellular Killing of bacteria. Previous studies have shown that Phg1A, Kil1 and Kil2 proteins are necessary for efficient Intracellular Killing of Klebsiella bacteria. Here we show that in phg1a KO cells, cellular levels of lysosomal glycosidases and lysozyme are decreased, and lysosomal pH is increased. Surprisingly, overexpression of Kil1 restores efficient Killing in phg1a KO cells without correcting these lysosomal anomalies. Conversely, kil1 KO cells are defective for Killing, but their enzymatic content and lysosomal pH are indistinguishable from WT cells. The Killing defect of phg1a KO cells can be accounted for by the observation that in these cells the stability and the cellular amount of Kil1 are markedly reduced. Since Kil1 is the only sulfotransferase characterized in Dictyostelium, an (unidentified) sulfated factor, defective in both phg1a and kil1 KO cells, may play a key role in Intracellular Killing of Klebsiella bacteria. In addition, Phg1B plays a redundant role with Phg1A in controlling cellular amounts of Kil1 and Intracellular Killing. Finally, cellular levels of Kil1 are unaffected in kil2 KO cells, and Kil1 overexpression does not correct the Killing defect of kil2 KO cells, suggesting that Kil2 plays a distinct role in Intracellular Killing.
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phg1 tm9 proteins control Intracellular Killing of bacteria by determining cellular levels of the kil1 sulfotransferase in dictyostelium
PLOS ONE, 2013Co-Authors: Marion Le Coadic, Anna Marchetti, Wanessa Cristina Lima, Romain Bruno Froquet, Marco Dias, Pierre CossonAbstract:Dictyostelium discoideum has largely been used to study phagocytosis and Intracellular Killing of bacteria. Previous studies have shown that Phg1A, Kil1 and Kil2 proteins are necessary for efficient Intracellular Killing of Klebsiella bacteria. Here we show that in phg1a KO cells, cellular levels of lysosomal glycosidases and lysozyme are decreased, and lysosomal pH is increased. Surprisingly, overexpression of Kil1 restores efficient Killing in phg1a KO cells without correcting these lysosomal anomalies. Conversely, kil1 KO cells are defective for Killing, but their enzymatic content and lysosomal pH are indistinguishable from WT cells. The Killing defect of phg1a KO cells can be accounted for by the observation that in these cells the stability and the cellular amount of Kil1 are markedly reduced. Since Kil1 is the only sulfotransferase characterized in Dictyostelium, an (unidentified) sulfated factor, defective in both phg1a and kil1 KO cells, may play a key role in Intracellular Killing of Klebsiella bacteria. In addition, Phg1B plays a redundant role with Phg1A in controlling cellular amounts of Kil1 and Intracellular Killing. Finally, cellular levels of Kil1 are unaffected in kil2 KO cells, and Kil1 overexpression does not correct the Killing defect of kil2 KO cells, suggesting that Kil2 plays a distinct role in Intracellular Killing.
Pierre Cosson - One of the best experts on this subject based on the ideXlab platform.
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Intracellular Killing of bacteria: is Dictyostelium a model macrophage or an alien?
Cellular microbiology, 2014Co-Authors: Pierre Cosson, Wanessa Cristina LimaAbstract:Predation of bacteria by phagocytic cells was first developed during evolution by environmental amoebae. Many of the core mechanisms used by amoebae to sense, ingest and kill bacteria have also been conserved in specialized phagocytic cells in mammalian organisms. Here we focus on recent results revealing how Dictyostelium discoideum senses and kills non-pathogenic bacteria. In this model, genetic analysis of Intracellular Killing of bacteria has revealed a surprisingly complex array of specialized mechanisms. These results raise new questions on these processes, and challenge current models based largely on studies in mammalian phagocytes. In addition, recent studies suggest one additional level on complexity by revealing how Dictyostelium recognizes specifically various bacterial species and strains, and adapts its metabolism to process them. It remains to be seen to what extent mechanisms uncovered in Dictyostelium are also used in mammalian phagocytic cells.
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Phg1/TM9 proteins control Intracellular Killing of bacteria by determining cellular levels of the Kil1 sulfotransferase in Dictyostelium.
PloS one, 2013Co-Authors: Marion Le Coadic, Anna Marchetti, Wanessa Cristina Lima, Romain Bruno Froquet, Marco Dias, Pierre CossonAbstract:Dictyostelium discoideum has largely been used to study phagocytosis and Intracellular Killing of bacteria. Previous studies have shown that Phg1A, Kil1 and Kil2 proteins are necessary for efficient Intracellular Killing of Klebsiella bacteria. Here we show that in phg1a KO cells, cellular levels of lysosomal glycosidases and lysozyme are decreased, and lysosomal pH is increased. Surprisingly, overexpression of Kil1 restores efficient Killing in phg1a KO cells without correcting these lysosomal anomalies. Conversely, kil1 KO cells are defective for Killing, but their enzymatic content and lysosomal pH are indistinguishable from WT cells. The Killing defect of phg1a KO cells can be accounted for by the observation that in these cells the stability and the cellular amount of Kil1 are markedly reduced. Since Kil1 is the only sulfotransferase characterized in Dictyostelium, an (unidentified) sulfated factor, defective in both phg1a and kil1 KO cells, may play a key role in Intracellular Killing of Klebsiella bacteria. In addition, Phg1B plays a redundant role with Phg1A in controlling cellular amounts of Kil1 and Intracellular Killing. Finally, cellular levels of Kil1 are unaffected in kil2 KO cells, and Kil1 overexpression does not correct the Killing defect of kil2 KO cells, suggesting that Kil2 plays a distinct role in Intracellular Killing.
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phg1 tm9 proteins control Intracellular Killing of bacteria by determining cellular levels of the kil1 sulfotransferase in dictyostelium
PLOS ONE, 2013Co-Authors: Marion Le Coadic, Anna Marchetti, Wanessa Cristina Lima, Romain Bruno Froquet, Marco Dias, Pierre CossonAbstract:Dictyostelium discoideum has largely been used to study phagocytosis and Intracellular Killing of bacteria. Previous studies have shown that Phg1A, Kil1 and Kil2 proteins are necessary for efficient Intracellular Killing of Klebsiella bacteria. Here we show that in phg1a KO cells, cellular levels of lysosomal glycosidases and lysozyme are decreased, and lysosomal pH is increased. Surprisingly, overexpression of Kil1 restores efficient Killing in phg1a KO cells without correcting these lysosomal anomalies. Conversely, kil1 KO cells are defective for Killing, but their enzymatic content and lysosomal pH are indistinguishable from WT cells. The Killing defect of phg1a KO cells can be accounted for by the observation that in these cells the stability and the cellular amount of Kil1 are markedly reduced. Since Kil1 is the only sulfotransferase characterized in Dictyostelium, an (unidentified) sulfated factor, defective in both phg1a and kil1 KO cells, may play a key role in Intracellular Killing of Klebsiella bacteria. In addition, Phg1B plays a redundant role with Phg1A in controlling cellular amounts of Kil1 and Intracellular Killing. Finally, cellular levels of Kil1 are unaffected in kil2 KO cells, and Kil1 overexpression does not correct the Killing defect of kil2 KO cells, suggesting that Kil2 plays a distinct role in Intracellular Killing.
Limin Zheng - One of the best experts on this subject based on the ideXlab platform.
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Arachidonic acid, but not its metabolites, is essential for FcγR‐stimulated Intracellular Killing of Staphylococcus aureus by human monocytes
Immunology, 1999Co-Authors: Limin Zheng, R. Van Furth, M. T. Van Den Barselaar, T. P. L. Zomerdijk, M. F. Geertsma, P. H. NibberingAbstract:Since arachidonic acid (AA) production by phospholipase A2 (PLA2) is essential for the Fcγ receptor (FcγR)-mediated respiratory burst and phagocytosis of opsonized erythrocytes by monocytes and macrophages, we focused in this study on the role of AA and its metabolites in the FcγR-stimulated Intracellular Killing of Staphylococcus aureus by human monocytes. The results revealed that the PLA2 inhibitors, but not inhibitors of cyclo-oxygenase and lipoxygenase, markedly suppressed the FcγR-mediated Killing process. The production of O−2 by monocytes upon FcγR cross-linking was inhibited by 4-bromophenacyl bromide in a dose-dependent fashion, indicating that inhibition of PLA2 activity impairs the oxygen-dependent bactericidal mechanisms of monocytes, which could be partially restored by addition of exogenous AA and docosahexaenoic acid, but not myristic acid. These polyunsaturated fatty acids, but not myristic acid, stimulated the Intracellular Killing of S. aureus by monocytes, although not as effectively as FcγR cross-linking. Furthermore, FcγR cross-linking stimulated the release of AA from monocytes. Studies with selective inhibitors revealed that the FcγR-mediated activation of PLA2 is dependent on Ca2+ and tyrosine kinase activity. Together these results indicate a key role for PLA2/AA, but not its major metabolites, in mediating the FcγR-stimulated Intracellular Killing of S. aureus by monocytes.
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Protein tyrosine kinase activity is essential for Fc gamma receptor-mediated Intracellular Killing of Staphylococcus aureus by human monocytes.
Infection and immunity, 1994Co-Authors: Limin Zheng, P. H. Nibbering, T. P. L. Zomerdijk, R. Van FurthAbstract:Our previous study revealed that the Intracellular Killing of Staphylococcus aureus by human monocytes after cross-linking Fc gamma receptor I (Fc gamma RI) or Fc gamma RII is a phospholipase C (PLC)-dependent process. The aim of the present study was to investigate whether protein tyrosine kinase (PTK) activity plays a role in the Fc gamma R-mediated Intracellular Killing of bacteria and activation of PLC in these cells. The results showed that phagocytosis of bacteria by monocytes was not affected by the PTK inhibitors genistein and tyrphostin-47. The Intracellular Killing of S. aureus by monocytes after cross-linking Fc gamma RII or Fc gamma RII with anti-Fc gamma R monoclonal antibody and a bridging antibody or with human immunoglobulin G (IgG) was inhibited by these compounds in a dose-dependent fashion. The production of O2- by monocytes after stimulation with IgG or IgG-opsonized S. aureus was almost completely blocked by the PTK inhibitor. These results indicate that inhibition of PTK impairs the oxygen-dependent bactericidal mechanisms of monocytes. Genistein and tyrphostin-47, which do not affect the enzymatic activity of purified PLC, prevented activation of PLC after cross-linking Fc gamma RI or Fc gamma RII, measured as an increase in the Intracellular inositol 1,4,5-trisphosphate concentration. Cross-linking Fc gamma RI or Fc gamma RII induced rapid tyrosine phosphorylation of several proteins in monocytes, one of which was identified as PLC-gamma 1, and the phosphorylation could be completely blocked by PTK inhibitors, leading to the conclusion that activation of PLC after cross-linking Fc gamma R in monocytes is regulated by PTK activity. Together, these results demonstrate that PTK activity is essential for the activation of PLC which is involved in the Fc gamma R-mediated Intracellular Killing of S. aureus by human monocytes.
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Stimulation of the Intracellular Killing of Staphylococcus aureus by human monocytes mediated by Fc gamma receptors I and II.
European journal of immunology, 1993Co-Authors: Limin Zheng, Peter H. Nibbering, Ralph Van FurthAbstract:Previous studies have shown that Intracellular Killing of bacteria by monocytes is stimulated by interaction between IgG and Fc gamma receptors (Fc gamma R) in the membrane of these cells. In the present study anti-Fc gamma R monoclonal antibodies (mAb) were used to investigate the relative contributions of the various classes of Fc gamma R to the Intracellular Killing of Staphylococcus aureus by human monocytes and the biochemical pathways involved. Anti-Fc gamma RI or anti-Fc gamma RII mAb, but not anti-Fc gamma RIII mAb, efficiently stimulated the Intracellular Killing of bacteria by monocytes. Cross-linking Fc gamma RI or Fc gamma RII, but not Fc gamma RIII, on monocytes with mouse anti-Fc gamma R mAb followed by bridging with F(ab')2 fragments of goat anti-mouse IgG enhanced this process. Since the NADPH oxidase inhibitor diphenyleneiodonium blocked the Fc gamma R-mediated Intracellular Killing of S. aureus, oxygen-dependent bactericidal mechanisms are most probably involved. Cross-linking Fc gamma RI or Fc gamma RII but not binding of the mAb to the Fc gamma R on monocytes activated phospholipase C, as demonstrated by the increase in the Intracellular concentration of inositol-(1,4,5)-triphosphate. The enhanced Intracellular Killing stimulated by cross-linking Fc gamma R on monocytes was completely blocked by U-73122, an inhibitor of phospholipase C-dependent processes. Protein kinase C activity, but not the rise in the cytosolic free Ca++ concentration or pertussis toxin-sensitive G proteins, is essential for the Fc gamma R-mediated Intracellular Killing of bacteria by monocytes. Together, these results demonstrate that cross-linking Fc gamma RI or Fc gamma RII is equally effective in stimulating the Intracellular Killing of bacteria by monocytes and that this stimulation is a phospholipase C-dependent process.
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Cytosolic free calcium is essential for immunoglobulin G-stimulated Intracellular Killing of Staphylococcus aureus by human monocytes.
Infection and immunity, 1992Co-Authors: Limin Zheng, P. H. Nibbering, R. Van FurthAbstract:Earlier studies have shown that the Intracellular Killing of Staphylococcus aureus by human monocytes requires continuous stimulation by serum factors, e.g., immunoglobulin G (IgG). In the present study, we demonstrate that IgG, at concentrations that stimulate the Intracellular Killing of S. aureus, induces a transient increase in the Intracellular free calcium concentration ([Ca2+]i) in monocytes. The Ca2+ ionophores A23187 and ionomycin stimulate the Killing process as efficiently as IgG does and initiate O2- production in resting monocytes but not in monocytes containing bacteria. The Ca2+ ionophore-stimulated Killing process was markedly inhibited by the NADPH oxidase inhibitor diphenyleneiodonium bisulfate, which indicates that these ionophores stimulate oxygen-dependent bactericidal mechanisms. Reduction of the [Ca2+]i to values below 1 nM, obtained by loading monocytes with MAPT/AM (1,2-bis-5-methyl-aminophenoxylethane-N,N,N',N'-tetraacetoxymet hyl acetate) in the absence of extracellular Ca2+, rendered the cells unresponsive to IgG or Ca2+ ionophore stimulation of the Intracellular Killing of S. aureus, but the response could be restored by reincubating these cells in the presence of extracellular Ca2+. It is concluded that cytosolic free Ca2+ is essential for the IgG-stimulated Intracellular Killing of S. aureus by human monocytes.
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The role of calcium and protein kinase C in the Intracellular Killing of bacteria by human monocytes
Mononuclear Phagocytes, 1992Co-Authors: Limin Zheng, P. H. Nibbering, R. Van FurthAbstract:Optimal Intracellular Killing of bacteria by human granulocytes and monocytes requires extracellular stimulation by immunoglobulins and complements factors (1–3). Interactions between these serum proteins and their corresponding receptors on the surface of phagocytes initiates Intracellular signalling which determines the functional activities of these cells under specific conditions (4).
S. L. Nielsen - One of the best experts on this subject based on the ideXlab platform.
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Extracellular and Intracellular Killing in neutrophil granulocytes of Staphylococcus aureus with rifampicin in combination with dicloxacillin or fusidic acid
Journal of Antimicrobial Chemotherapy, 1999Co-Authors: S. L. Nielsen, F. T. BlackAbstract:The effect of rifampicin in combination with dicloxacillin or fusidic acid on the extracellular and Intracellular Killing of Staphylococcus aureus in human neutrophil granulocytes in the presence of serum was studied. At the extracellular level rifampicin significantly reduced the bactericidal activity of dicloxacillin, but had an indifferent effect on the activity of fusidic acid. The combination of rifampicin with dicloxacillin or fusidic acid led to Intracellular Killing no different from that produced by rifampicin alone. However, owing to the high Intracellular activity of rifampicin, the Intracellular Killing by the drug combinations was greater than that by dicloxacillin or fusidic acid alone.
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The effect of dicloxacillin and fusidic acid on the extracellular and Intracellular Killing of Staphylococcus aureus.
The Journal of antimicrobial chemotherapy, 1998Co-Authors: S. L. Nielsen, F. T. BlackAbstract:The effect of dicloxacillin and fusidic acid used alone and in combination on the extracellular and Intracellular Killing of four isolates of Staphylococcus aureus in the presence of serum was studied. At the extracellular level, dicloxacillin (8 mg/L) had a bactericidal effect on all four isolates, whereas fusidic acid (64 mg/L) had a bacteriostatic effect on two isolates and no effect on the two other isolates. Fusidic acid significantly inhibited the extracellular bactericidal effect of dicloxacillin on two isolates. Intracellular Killing was measured in human neutrophil granulocytes. Dicloxacillin (8 mg/L) significantly increased the Intracellular Killing of all four isolates, while fusidic acid (64 mg/L) significantly increased the Intracellular Killing of three isolates, but the Killing was significantly lower than that of dicloxacillin. When the antibiotics were combined the Intracellular Killing of three of the isolates was significantly lower than that of dicloxacillin alone. The viability of the granulocytes and their ability to produce superoxide anion were not affected by the antibiotics. In conclusion, we found that the increased Intracellular Killing of S. aureus by dicloxacillin was inhibited by fusidic acid.
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The effect of quinolones on the Intracellular Killing of Staphylococcus aureus in neutrophil granulocytes.
Journal of Antimicrobial Chemotherapy, 1997Co-Authors: S. L. Nielsen, Niels Obel, Merete Storgaard, Paul L. AndersenAbstract:The effect of ciprofloxacin, lomefloxacin, fleroxacin and ofloxacin on the Intracellular Killing of Staphylococcus aureus in human neutrophil granulocytes was studied. Each drug was tested in concentrations of 0.25, 1, 4, 16 and 64 times the MIC and the Intracellular Killing was measured for up to 5 h of incubation. All four quinolones increased the Intracellular Killing in a concentration- and time-dependent manner. When compared at concentrations of 4 x MIC, ofloxacin increased the Killing significantly more than the other quinolones. All four quinolones Increased the Killing significantly more than the β-lactam dicloxacillin. All five antibiotics increased the Killing significantly relative to the control without antibiotics. None of the antibiotics affected the viability of the granulocytes or their ability to generate super-oxide anion. In conclusion, the quinolones increased the Intracellular Killing of S. aureus in neutrophil granulocytes.
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The effect of quinolones on the Intracellular Killing of Staphylococcus aureus in neutrophil granulocytes.
The Journal of antimicrobial chemotherapy, 1997Co-Authors: S. L. Nielsen, Niels Obel, Merete Storgaard, Paul L. AndersenAbstract:The effect of ciprofloxacin, lomefloxacin, fleroxacin and ofloxacin on the Intracellular Killing of Staphylococcus aureus in human neutrophil granulocytes was studied. Each drug was tested in concentrations of 0.25, 1, 4, 16 and 64 times the MIC and the Intracellular Killing was measured for up to 5 h of incubation. All four quinolones increased the Intracellular Killing in a concentration- and time-dependent manner. When compared at concentrations of 4 x MIC, ofloxacin increased the Killing significantly more than the other quinolones. All four quinolones increased the Killing significantly more than the beta-lactam dicloxacillin. All five antibiotics increased the Killing significantly relative to the control without antibiotics. None of the antibiotics affected the viability of the granulocytes or their ability to generate superoxide anion. In conclusion, the quinolones increased the Intracellular Killing of S. aureus in neutrophil granulocytes.
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Evaluation of a method for measurement of Intracellular Killing of Staphylococcus aureus in human neutrophil granulocytes
APMIS : acta pathologica microbiologica et immunologica Scandinavica, 1995Co-Authors: S. L. Nielsen, F. T. Black, Merete Storgaard, Niels ObelAbstract:A modified method for measurement of Intracellular Killing of Staphylococcus aureus in human neutrophil granulocytes is described. After phagocytosis of S. aureus the extracellular bacteria were sufficiently removed by repeated centrifugations and washings of the granulocytes. The optimal conditions for incubation of granulocytes for measurement of Intracellular Killing were found to be 37 degrees C in the presence of 5% CO2. Under these conditions, stable pH, the viability and the capacity of the granulocytes for superoxide anion generation were preserved. The number of Intracellular viable bacteria was determined after lysis of the granulocytes, which should be done in H2O at pH 11 to ensure sufficient cell lysis. The kinetics and individual variation of the Intracellular Killing are described. The intra- or extracellular location of surviving bacteria was studied. After approximately 8 h incubation we observed Intracellular growth of S. aureus followed by lysis of granulocytes and extracellular growth of bacteria. Consequently, the incubation period should not be extended beyond 5 to 8 h when the assay is used to study the effects of antibiotics on Intracellular Killing.
