Methods for assessing exocytosis by neutrophil leukocytes.
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Animals↗
Biomedical subjects
M Baggiolini
Publications and source records attributed to M Baggiolini.
Measurement of hydrogen peroxide production by phagocytes using homovanillic acid and horseradish peroxidase.
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Animals↗
Quantitative analysis of the cytosolic free calcium dependency of exocytosis from three subcellular compartments in intact human neutrophils.
Cytosolic free calcium concentration, [Ca2+]i, and exocytosis of azurophil granules (beta-glucuronidase), specific granules (vitamin B12-binding protein), and secretory vesicles (gelatinase) were measured concomitantly in intact human neutrophils under steady state [Ca2+]i. The cells were loaded with the fluorescent calcium indicator quin2 in the presence or absence of extracellular Ca2+, and steady state [Ca2+]i levels ranging from 20 to greater than 2,000 nM were obtained by adding the Ca2+ ionophore ionomycin at various concentrations of extracellular calcium. The extent of exocytosis from the three granule populations was found to be a function of [Ca2+]i. The minimal [Ca2+]i that caused significant release (threshold [Ca2+]i) was approximately 200-300 nM and was similar for all three compartments. Marked differences, however, were found when the [Ca2+]i for half-maximal exocytosis (EC50) was determined. In the absence of cytochalasin B the EC50 was 1,100 +/- 220 nM and 1,600 +/- 510 nM for specific granules and secretory vesicles, respectively, and approximately 6,000 nM for azurophil granules. Cytochalasin B did not affect the threshold [Ca2+]i but decreased the EC50 and enhanced the rate of exocytosis. In the presence of cytochalasin B the EC50 was approximately 600 nM both for secretory vesicles and specific granules, and approximately 2,600 nM for azurophil granules. The addition of the chemotactic peptide N-formyl-methionyl-leucyl-phenylalanine dramatically changed the [Ca2+]i dependency of granule secretion: It decreased the threshold [Ca2+]i to less than 20 and less than 50 nM, and the EC50 to 50 and 200 nM for specific and azurophil granules, respectively, and it significantly increased the rate of exocytosis. Thus, the additional signal(s) provided by receptor activation markedly lower(s) the Ca2+ requirement of the exocytotic process. Furthermore, these results indicate that the secretion from three different granule populations within the same cell type are differently modulated by [Ca2+]i.
Calcium↗
Absence of platelet membrane glycoproteins IIb/IIIa from monocytes.
Two-dimensional gel electrophoresis, immunoprecipitation, and crossed immunoelectrophoresis were used in the investigation of glycoproteins IIb/IIIa in platelets, monocytes, and monocyte-derived macrophages from human blood. All techniques detected the glycoproteins in platelets but not in the mononuclear phagocytes. Similar results were obtained by immunochemistry using a monoclonal antibody against the platelet glycoproteins IIb/IIIa (revealed by a gold-labeled second antibody) which bound heavily to the platelet but not to the monocyte surface. The biochemical techniques used for the analysis of mononuclear phagocytes would have reliably detected the level of glycoproteins IIb/IIIa contributed by a 5% contamination with platelets, calculated on a per cell basis. We conclude that human monocytes and monocyte-derived macrophages lack glycoproteins IIb/IIIa. Our results further indicate that centrifugal elutriation yields monocyte preparations with minimal contamination by platelets. It seems likely that the positive results obtained by other authors were due to the presence of platelets or fragments on the monocytes.
Antibodies, Monoclonal↗
Activation of NADPH oxidase in human neutrophils. Synergism between fMLP and the neutrophil products PAF and LTB4.
The induction of the respiratory burst in human neutrophils by combinations of fMLP and either PAF or LTB4 was studied. Pretreatment with PAF (0.0001 to 10 uM), which by itself did not elicit the burst, greatly enhanced the rate and extent of fMLP-induced superoxide production. A synergism of a different kind was observed with the reversed stimulus sequence: Pretreatment with fMLP made the neutrophils capable to respond to PAF with superoxide production. A moderate enhancement of the fMLP response was also obtained following pretreatment with LTB4. The response of the cells to LTB4, however, was not influenced by fMLP, and no synergism was observed between the two neutrophil products PAF and LTB4. The results of this study demonstrate a marked synergism between fMLP and PAF and suggest that PAF may function as an amplifier of the respiratory burst response of stimulated neutrophils.
Drug Synergism↗
Effect of benzydamine on exocytosis and respiratory burst in human neutrophils and mononuclear phagocytes.
The effect of benzydamine on stimulus-dependent respiratory burst activity and enzyme release was tested in human neutrophils, monocytes and monocyte-derived macrophages. Established anti-inflammatory compounds, indomethacin, phenylbutazone and bufexamac, were tested for comparison. Care was taken to avoid cytotoxic or cytolytic concentrations of the test compounds, and their effect on release of lactate dehydrogenase was also tested. Release of specific and azurophil granules contents were induced in human neutrophils by A23187, PMA and fMLP with and without cytochalasin B pretreatment. Benzydamine inhibited stimulus-dependent release of vitamin B12-binding proteins, a marker for the specific granules, in a concentration-dependent fashion. By contrast, phenylbutazone and bufexamac were practically inactive. The effect of benzydamine on exocytosis of azurophil granules was tested in cytochalasin B-pretreated neutrophils. Benzydamine, again in contrast to the two reference anti-inflammatory compounds, inhibited release concentration-dependently also under these conditions. The concentration of the compound which inhibited exocytosis by 50% was 30-100 microM in normal and 3-10 microM in cytochalasin B-treated neutrophils. The effect of benzydamine and reference compounds on the respiratory burst was tested by assaying for superoxide formation in neutrophils and H2O2 formation in mononuclear phagocytes. Benzydamine was inactive on neutrophils and inhibited slightly the burst response of monocytes and macrophages. Two reference compounds, bufexamac and phenylbutazone, were generally more active. The strongest inhibitory effect was that of phenylbutazone on fMLP-stimulated cells. Benzydamine lacked activity under these conditions, indicating that it does not bind to the receptor of formylated chemotactic peptides.(ABSTRACT TRUNCATED AT 250 WORDS)
Benzydamine↗
Identification of three types of granules in neutrophils of ruminants. Ultrastructure of circulating and maturing cells.
The production of three populations of granules during maturation and their occurrence in the neutrophils of a number of ruminants is described. Bone marrow samples from cows, sheep, and goats were fixed, reacted for peroxidase, and examined by transmission electron microscopy. Granule formation was found to occur at three subsequent stages. As in other species including man, it begins with the production of peroxidase-positive granules and is concluded with the production of moderately dark-staining, peroxidase-negative granules of similar size. These two organelles have the characteristics of the azurophil or primary and specific or secondary granules of other species. At an intermediate stage, a different type of peroxidase-negative granule, the large granule, is formed. Its profile is round and markedly larger than those of azurophil and specific granules. The large granules initially have a loose, undulated membrane and fill gradually with matrix which in early forms consists of a central core. Fully developed large granules have a sharply defined membrane and a pale, very uniform content. The two types of peroxidase-negative granules can be distinguished by their sizes and times of formation and also by the appearance of their content which is more coarse and darker in the specific granules. Mature neutrophils from cows, goats, sheep, and an ibex were also examined. Two features are common to all cells viewed: the presence of three types of granules and the preponderance of the large granule population. The results of this study, together with evidence from cell fractionation experiments, suggest that the large granules are a characteristic property of the neutrophils of ruminants.
Animals↗
Activation of NADPH oxidase of human neutrophils. Potentiation of chemotactic peptide by a diacylglycerol.
Formyl-methionyl-leucyl-phenylalanine (fMLP) and 1-oleoyl-2-acetyl-glycerol (OAG) are synergistic stimuli of the respiratory burst of neutrophils. Simultaneous exposure to both agents greatly enhanced superoxide production, both in rate and extent. OAG potentiated the response to fMLP also in Ca++ -free medium. Pretreatment of the neutrophils with fMLP drastically shortened the lag of superoxide production in response to OAG. Our findings lead to the following conclusions: (i) Protein kinase C is likely to be involved in the activation of the NADPH oxidase by fMLP; (ii) OAG appears to be utilized as an intermediate in the activation process; (iii) prestimulation of the cells with fMLP facilitates the response to OAG.
Cytochrome c Group↗
Phagocytes use oxygen to kill bacteria.
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Bacteria↗
Influence of macrophage products on the release of plasminogen activator, collagenase, beta-glucuronidase and prostaglandin E2 by articular chondrocytes.
We describe the effects of products of mononuclear phagocytes on the secretory activity of chondrocytes. The primary confluent cultures of rabbit articular chondrocytes were exposed to standard medium alone or enriched with conditioned medium obtained from cultures of rabbit peritoneal macrophages, the mouse macrophage cell line P388D1 or human blood mononuclear cells. Four markers of release were assessed, the neutral proteinases plasminogen activator and collagenase, the acid hydrolase beta-glucuronidase and prostaglandin E2, and the kinetics of their changes were monitored. Chondrocytes that were cultured in standard medium secreted large amounts of plasminogen activator, some beta-glucuronidase, but no collagenase, and released only minor amounts of prostaglandin E2. The addition of conditioned medium from rabbit macrophages induced a rapid release of large quantities of prostaglandin E2 and an abundant secretion of collagenase, while abolishing or strongly decreasing plasminogen activator secretion. In addition, beta-glucuronidase secretion was markedly enhanced. The decrease in secretion of plasminogen activator appeared to reflect a diminished production, since no evidence was found for the generation of inhibitors or for an accelerated extracellular breakdown of the enzyme. Conditioned media of the mouse and human mononuclear cells influenced the secretory activities of rabbit articular chondrocytes in a similar way, suggesting that the factor (or factors) acting on chondrocytes is produced by a variety of macrophages, and that its action is not species-restricted. The time course and concentration-dependence of the effects observed indicate that the secretion of plasminogen activator and collagenase are influenced in a strictly reciprocal fashion by the macrophage products. The release of prostaglandin E2 paralleled that of collagenase.
Animals↗
Immunomodulatory effects of Panax Ginseng C.A. Meyer in the mouse.
An aqueous extract of Panax Ginseng C.A. Meyer (G.S.) was prepared by boiling crushed G.S. roots in water. The extract obtained was adjusted to 125 mg G.S. per ml and was administered orally to mice for 5 to 6 days at the daily dose of 10, 50 and 250 mg G.S. per kg or was added to cultures of mouse spleen cells at concentrations varying between 0.25 and 8 mg G.S. per ml. The average total ginsenoside content of the G.S. roots used was determined by HPLC analysis and found to be 0.58% (w/w). Treated mice responded with enhanced antibody formation to either a primary or a secondary challenge with sheep red cells. The effects were dose-dependent. At the highest dose regimen, the primary IgM response was increased by 50% and the secondary IgG and IgM responses were increased by 50 and 100%, respectively. An even more pronounced effect was obtained with natural killer cell activity which was enhanced between 44 and 150% depending on the effector-to-target cell ratios used in the assay. In vitro, G.S. showed two main effects, an inhibition of stimulated and spontaneous lymphocyte proliferation at high, but not cytotoxic concentrations and an enhancement of interferon production particularly in non-stimulated spleen cells. The immunostimulating effects obtained in vivo are in agreement with the stimulation of interferon production observed in vitro. The inhibition of lymphocyte proliferation, however, cannot be reconciled with the immunostimulatory action of G.S. observed in vivo.
Animals↗
Intracellular parasite killing induced by electron carriers. II. Correlation between parasite killing and the induction of oxidative events in macrophages.
Mouse peritoneal macrophages infected with Leishmania parasites were exposed in vitro to the electron carriers methylene blue (MB), toluidine blue 0 (TB), phenazine methosulfate (PMS) and crystal violet (CV). This led to parasite destruction without harm to the macrophages. The kinetics of intracellular killing depended on both the drug concentration and the duration of exposure; over 80% of the microorganisms were inactivated within 2.5 min of incubation of the parasitized cells with 10(-4) M MB. On a molar basis, the drugs were considerably more active against intracellular compared to free parasites, suggesting that the macrophages themselves play a role in the observed anti-parasite toxicity. Intracellular killing by macrophages exposed to MB, TB and PMS correlated with the stimulation of oxygen uptake and hexose monophosphate shunt activity in the cells. Cytochrome c markedly inhibited MB-induced intracellular parasite destruction as well as completely blocking parasite killing in macrophages activated by lymphokines, pointing to O-2, H2O2 or products derived therefrom as possible mediators of macrophage toxic activity in both instances. Cytochrome c did not protect free parasites from the direct toxicity of the drug, however. Lipopolysaccharide promoted parasite destruction by lymphokine-activated macrophages, but failed to do so for electron carrier-stimulated cells. These observations suggest that intracellular killing induced by electron carriers results from a direct interaction of the drugs with cellular redox systems, leading to the generation of oxygen metabolites toxic for the parasites.
Animals↗
Stimulation of phagocytosis in bone marrow-derived mouse macrophages by bacterial lipopolysaccharide: correlation with biochemical and functional parameters.
It has been shown that low concentrations of E. coli lipopolysaccharides (LPS) greatly and selectively stimulate phagocytosis and related functions in mouse bone marrow-derived macrophages. Culture in the presence of 50 ng/ml LPS induced on average a 10-fold enhancement of phagocytosis of IgG-coated sheep erythrocytes. Activation was in two stages--a small increase observed during the first 8 to 12 hr, and the major increase noted between 16 and 24 hr. Phagocytic activity remained at the maximal level for 24 hr and then declined progressively. Stimulation by LPS was dose-dependent; significant effects could be observed at 0.8 ng/ml and the maximum was reached at 10 ng/ml. LPS-treated cells also showed a markedly increased tendency to form colonies. All these effects could be prevented by the addition of 100 ng/ml polymyxin B together with LPS, indicating that the active principle is lipid A. The LPS-dependent increase in phagocytic activity is probably mediated by increased Fc receptor capacity because both parameters were influenced in parallel by the stimulus. Phagocytosis-related events, such as enhanced hexose monophosphate shunt activity, H2O2 formation, and nitroblue tetrazolium reduction were also stimulated by LPS. By contrast, pinocytosis was unaffected. Measurements of cell-associated enzyme activities showed that lactate dehydrogenase, acid phosphatase, and cathepsin D were significantly increased. Beta-glucuronidase, beta-galactosidase, alkaline phosphodiesterase, and aminopeptidase were unchanged and NAD nucleosidase was markedly decreased after LPS treatment. 5'-Nucleotidase and glucosamine uptake were undetectable both in control and LPS-stimulated cells. LPS treatment induced a significant increase in cell-associated protein, but did not result in cell proliferation or increased cell loss as shown by the DNA content that remained constant. LPS-induced changes were dependent on de novo protein synthesis; cycloheximide prevented enhancement of phagocytosis, Fc receptor capacity, and colony formation.
Animals↗
Assay of H2O2 production by macrophages and neutrophils with homovanillic acid and horse-radish peroxidase.
A simple and sensitive method for measurement of the release of H2O2 from phagocytic cells is described. The assay is based on the H2O2-dependent oxidation of homovanillic acid (3-methoxy-4-hydroxyphenylacetic acid, HVA) to a highly fluorescent dimer (2,2'-dihydroxy-3,3'-dimethoxydiphenyl-5,5'-diacetic acid) which is mediated by horse-radish peroxidase. A linear relationship between fluorescence (lambda ex = 312 nm and lambda em = 420 nm) and amount of H2O2 was found in the range of 0.1-10 nmoles per 2.25 ml assay. The method was reliable for monitoring H2O2 production in large numbers of cell samples, as suspensions or monolayers, over periods of time extending between minutes and several hours. At concentrations optimal for detection of cellular release of H2O2, HVA and horse-radish peroxidase were devoid of cytotoxic effects. The time course of H2O2 release by mouse peritoneal and bone marrow-derived macrophages and by human neutrophils was determined following stimulation with zymosan particles or phorbol myristate acetate, and the dependence of H2O2 release on cell number and stimulus dosage was studied.
Animals↗
Exocytosis induced in neutrophils by chemotactic agents and other stimuli.
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Calcimycin↗
A novel type of cytoplasmic granule in bovine neutrophils.
We obtained cell preparations containing greater than 95% neutrophils from freshly drawn bovine blood. The cells were suspended in sucrose and disrupted in a Dounce homogenizer, and the postnuclear supernate was fractionated by zonal differential sedimentation and by isopycnic equilibration. The subcellular fractions were characterized biochemically by testing for marker enzymes and other constituents known to occur in azurophil and specific granules of other species, and by electrophoretic analysis of extracts of the particulate material. In addition, each fraction was examined by random-sampling electron microscopy. We found that bovine neutrophils contain in addition to azurophil and specific granules a third type of granule, not known to occur in neutrophils of other species. These novel granules are larger, denser, and considerably more numerous than the two other types. Except for lactoferrin, they lack the characteristic constituents of azurophil granules (peroxidase, acid hydrolases, and neutral proteinases) and of specific granules (vitamin B12-binding protein). Instead, they contain a group of highly cationic proteins not found in the other granules, and they are the exclusive stores of powerful oxygen-independent bactericidal agents. We studied the fate of the large granules in bovine neutrophils exposed to opsonized particles, the ionophore A 23187, or phorbol myristate acetate. The appearance in the cell-free media of antibacterial activity and of the characteristic highly cationic proteins as revealed by electrophoresis was monitored and compared with the release of azurophil and specific granule markers. In addition, changes of the relative size of the large granule compartment induced by phagocytosis were assessed by morphometry. The results show that exocytosis of the large granules occurs following both phagocytosis and exposure to soluble stimuli. Like the specific granules, the large granules appear to be discharged by true secretion under conditions where the azurophil granules are fully retained.
Animals↗