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G Weissmann

Publications and source records attributed to G Weissmann.

At least 109 records · Page 6Linked to original sources
PubMed1985

Adenosine; a physiologic modulator of superoxide anion generation by human neutrophils. Adenosine acts via an A2 receptor on human neutrophils.

Adenosine specifically inhibits superoxide anion generation by N-formyl-methionyl-leucyl-phenylalanine-stimulated neutrophils without affecting either degranulation or "aggregation." We present data that also supports the hypothesis that adenosine engages a specific cell surface receptor to mediate inhibition of stimulated neutrophils. Theophylline (10 and 100 mu M), a competitive antagonist at adenosine receptors, reversed the effects of adenosine (0.1 mu M) on superoxide anion generation by stimulated neutrophils. The adenosine analogue 5'N-ethylcarboxamidoadenosine (NECA) was a more potent inhibitor of superoxide anion generation than either N6-phenylisopropyladenosine (PIA) or adenosine, an order of potency consistent with that previously demonstrated for adenosine A2 receptors. 2-Chloroadenosine inhibited superoxide anion generation at concentrations similar to NECA. [3H]-NECA and [3H]-2-chloroadenosine bound to a single receptor on intact neutrophils. The characteristics of the receptors for [3H]-NECA and [3H]-2-chloroadenosine were similar (Kd = 0.22 and 0.23 mu M, respectively; number of binding sites = 9.31 and 11.1 X 10(3) sites/cell, respectively). NECA, 2-chloroadenosine, adenosine, and PIA inhibited binding of [3H]-NECA with a rank order similar to that for inhibition of superoxide anion generation (NECA = 2-chloroadenosine greater than adenosine greater than PIA). There was 50% inhibition of superoxide anion generation by NECA at approximately 20% receptor occupancy. Adenosine, derived from damaged tissues, may serve as a specific, endogenous modulator of superoxide anion generation by activated neutrophils through interaction at this newly described receptor on human neutrophils.

2-Chloroadenosine↗
PubMed1985

The first seconds of neutrophil activation: phosphoinositides, protein kinase C, and calcium movements.

Activation of the neutrophil by interaction of a ligand such as f-Met-Leu-Phe with its specific receptor elicits a prompt breakdown of PIP2 and the generation of PA via diacylglycerol. There is a rapid elevation of cytosolic calcium and activation of protein kinase C. Calcium and protein kinase C act synergistically to elicit the physiological responses. Although PIP2 breakdown and PA generation are prompt responses of neutrophils to receptor occupancy by chemoattractants, these steps can be bypassed by stimuli which directly activate protein kinase C or increase cytosolic calcium. Elevation of cytosolic Ca and activation of protein kinase C did not elicit breakdown of PIP2, indicating that phosphoinositide remodeling is not caused by activation of protein kinase C or by elevation of cytosolic calcium, nor is such a breakdown or the generation of phosphatidic acid required for the subsequent responses. The evidence indicates that PIP2 breakdown is an early event in stimulus-response coupling and is correlated with receptor-initiated generation of the signal.

Calcium↗
PubMed1985

From Beaumont to poison ivy: marine sponge cell aggregation and the secretory basis of inflammation.

We have studied Microciona prolifera cells as a model for inflammation and secretion. Dissociated in Ca-, Mg-free seawater with 2.5 mM EDTA, the cells aggregate when exposed to Ca (greater than 5 mM) and Ca ionophores. Extracellular Ca is not required over the course of aggregation; brief pulses of Ca suffice. Aggregation was induced by A23187 in excess EDTA after cells were prepared by pulse Ca. It appeared that Ca ionophore stimulated the secretion of Microciona aggregation factor (MAF) to a locus or in a form inaccessible to external EDTA. Pulse-induced aggregation depended on MAF because it was inhibited by MAF fragments, which are ligands for MAF-binding sites. Sponge cells were preloaded with three fluorescent dyes that monitor aspects of stimulus-secretion coupling: 1) 3,3'-dipropylthiadicarbocyanine iodide (dis-C3-(5)), a carbocyanine dye presumed to report changes in membrane potential; 2) 9-aminoacridine (9AA), which presumably reports secretion from acid vesicles; and 3) chlortetracycline (CTC), presumed to report mobilization of membrane-associated Ca. Exposure of cells either to constant Ca or to pulse Ca stimuli caused prompt decreases in the fluorescence of cells with diS-C3-(5) and increases in fluorescence of cells with 9AA. In contrast, although constant Ca provoked decreases in fluorescence of cells with CTC, a pulse Ca was without effect. Moreover, inhibitors of stimulus-response coupling (e.g., aspirin, sodium salicylate, 5 mM; diclofenac, 100 microM) inhibited sponge aggregation induced by either constant or pulse stimuli. In contrast, like the endogenous mediator of inflammation, leukotriene B4, trienoic alkyl catechols (urushiol) from poison ivy provoked aggregation. These studies suggest the utility of this marine model for analysis of stimulus-response coupling in cells of higher species that also respond to secretagogues in the absence of external Ca.

Aminacrine↗
PubMed1984

Inhibition of neutrophil activation by nonsteroidal anti-inflammatory drugs.

Nonsteroidal anti-inflammatory drugs are thought to prevent inflammation in rheumatoid arthritis by inhibiting prostaglandin synthesis. This observation does not explain, however, why nonsteroidal anti-inflammatory drugs are able to control inflammation caused by other mediators. To determine whether nonsteroidal anti-inflammatory drugs also exert an effect on neutrophil activation, in vitro and in vivo studies were undertaken. Aggregation, superoxide anion generation, and lysosomal enzyme release were assessed. The nonsteroidal anti-inflammatory drugs were found to inhibit these neutrophil responses, but the patterns of inhibition varied from drug to drug. These findings suggest that nonsteroidal anti-inflammatory drugs may have direct effects on neutrophil activation that are independent of their shared inhibition of prostaglandin synthesis.

Anti-Inflammatory Agents↗
PubMed1984

Calcium dependent aggregation of marine sponge cells is provoked by leukotriene B4 and inhibited by inhibitors of arachidonic acid oxidation.

Dissociated cells of the marine sponge, Microciona prolifera, aggregate in response to a species-specific aggregation factor (MAF) and Ca ionophores. We now report that leukotriene B4, a 5-lipoxygenase product, also causes aggregation of sponge cells. No other lipoxygenase products provoked aggregation. However, nordihydroguaiaretic acid (NDGA), colchicine, indomethacin, piroxicam and ibuprofen inhibited MAF-induced aggregation; the latter three agents inhibited Ca movements. Inhibition of prostaglandin release cannot be the mechanism whereby these agents inhibit aggregation of sponge cells, since the cells do not respond to exogenous cyclooxygenase products.

Animals↗
PubMed1984

Stimulus response coupling in the human neutrophil. I. Kinetic analysis of changes in calcium permeability.

The relationship between receptor-ligand interaction in human neutrophils and initiation of enhanced Ca permeability ("45Ca uptake") has been correlated with cell function. Different ligands varied in their efficacy in provoking 45Ca permeability changes: chemotactic peptide f-Met-Leu-Phe greater than concanavalin A greater than immune complexes greater than phorbol myristate acetate. Mixtures of stimuli at optimal concentrations elicited no summation of responses, indicating that interaction of f-Met-Leu-Phe, concanavalin A, and phorbol myristate acetate with their respective "receptors" regulates a common site of 45Ca uptake. The onset of Ca uptake was an early event, preceding onset of aggregation, O-2 generation, and degranulation. Enhanced 45Ca permeability during neutrophil activation is dependent on mobilization of intracellular Ca, since 8-(N,N-diethylamino)-octyl:3,4,5-trimethoxybenzoate hydrochloride was a potent inhibitor of the Ca permeability response. In contrast, calmodulin antagonists did not inhibit Ca permeability changes; the requirement for calmodulin in the physiological responses of aggregation, O-2 generation, and degranulation must therefore be subsequent to activation of the "Ca translocator." We propose a role for a "Ca-translocating mechanism" as an amplifying factor in neutrophil activation.

Antigen-Antibody Complex↗
PubMed1984

Stimulus response coupling in the human neutrophil. II. Temporal analysis of changes in cytosolic calcium and calcium efflux.

The role of changes in cytosolic free calcium (Ca) in the activation sequence of the human neutrophil has been monitored by means of the fluorescent probe Quin2. "Complete" secretagogues such as the chemotactic peptide f-Met-Leu-Phe and aggregated IgG, as well as the "incomplete" secretagogue concanavalin A, elicited prompt rises in cytosolic Ca. The rise in cytosolic Ca was in all cases one of the earliest measurable events, consistent with the hypothesis that increments in cytosolic free Ca serve as a signal to activate subsequent physiological responses. The source of cytosolic Ca is principally intracellular, since removal of extracellular Ca had little effect on the rise in cytosolic Ca. Although increments in cytosolic Ca may be essential for neutrophil activation, they are evidently not sufficient; chemotactic levels of f-Met-Leu-Phe elicited optimal increments in cytosolic Ca without triggering degranulation, O-2 generation, and aggregation. Some other factor, associated with high levels of receptor occupancy, must be required for secretion. The tumor promoter phorbol myristate acetate was an exceptional stimulus, since it elicited degranulation, aggregation, and O-2 generation without triggering a rise in cytosolic Ca. Finally, an efflux of Ca is initiated which serves to maintain low intracellular levels of Ca.

Biological Transport, Active↗
PubMed1984

Formation of leukotriene C4 by human leukocytes exposed to monosodium urate crystals.

Monosodium urate (MSU) crystals stimulate the metabolism of arachidonic acid in mixed populations of human leukocytes. Leukocytes exposed to MSU crystals released leukotriene C4. Leukotriene C4 (LTC4) was characterized and detected by high-performance liquid chromatography (HPLC), UV absorption, bioassay with guinea pig ileum, and radioimmunoassay. Results indicate that MSU crystals stimulate the transformation of arachidonic acid and the formation of leukotriene C4 in human leukocytes; an effect inhibited by colchicine. Moreover, they suggest that LTC4 may serve as a mediator of inflammation in crystal-associated diseases.

Chromatography, High Pressure Liquid↗
PubMed1984

Effects of non-steroidal anti-inflammatory agents on human neutrophil functions in vitro and in vivo.

Human blood neutrophils exposed to appropriate stimuli aggregate, degranulate and generate superoxide anion (O2-). These responses are anteceded by mobilization of membrane-associated calcium, monitored as a decrease in fluorescence of cells preloaded with chlortetracycline (CTC). We studied the effects, both in vitro and in vivo, of non-steroidal anti-inflammatory agents (aspirin, indomethacin, ibuprofen and piroxicam) on these neutrophil responses to three stimuli: a chemoattractant, N-formyl-methionyl-leucyl-phenylalanine (FMLP); a tumor promotor, phorbol myristate acetate (PMA); and a lectin, concanavalin A (Con A). The effects of these drugs were compared with those of two polyenoic inhibitors of arachidonate metabolism: eicosatrienoic acid (ETI) and eicosatetraynoic acid (ETYA). The pattern of inhibition of neutrophil functions varied both with inhibitor and the nature of the stimulus. Thus, aspirin, piroxicam, ETYA and ETI inhibited neutrophil aggregation, degranulation, and O2- generation in response to FMLP, whereas ibuprofen inhibited only aggregation and degranulation and indomethacin only inhibited aggregation. None of the agents inhibited aggregation or degranulation induced by PMA or Con A: only piroxicam inhibited O2- generation in response to PMA or Con A. ETI and ibuprofen inhibited decrements of CTC fluorescence induced by FMLP, but whereas ETI inhibited the CTC response to PMA or Con A, ibuprofen was without effect. The agents had varying effects on binding of the stimulus [( 3H]FMLP, [3H]Con A), but these did not correlate with neutrophil responses to the ligands. Neutrophils from subjects taking therapeutic doses of ibuprofen, indomethacin, or piroxicam showed profiles of inhibited responses to FMLP similar to those observed with these agents in vitro. These data suggest that, although non-steroidal anti-inflammatory agents may inhibit discrete neutrophil functions both in vitro and in vivo, their effects do not duplicate those of polyenoic inhibitors of arachidonate metabolism. Moreover, since the susceptibility of neutrophils differed not only with respect to each inhibitor, but also to the stimulus, it is unlikely that all neutrophil responses are necessarily linked by a common pathway that is blocked by inhibitors of arachidonic acid metabolism.

5,8,11,14-Eicosatetraynoic Acid↗
PubMed1984

Female hormones reduce neutrophil responsiveness in vitro.

Neutrophils were preincubated with 17 beta-estradiol and progesterone to determine the effects of these hormones on chemotactic peptide-stimulated superoxide anion (O2-) generation and degranulation. At pharmacologic levels 17 beta-estradiol was more active than progesterone with respect to inhibition of O2- generation as well as degranulation. An increase of preincubation time from 5 minutes to 25 minutes increased the percent inhibition. When 17 beta-estradiol and progesterone were combined at levels which approximate those measured during gestation, there was small but significant inhibition of O2- generation. Dexamethasone at equal molar concentration inhibited O2- generation only after 25 minutes of preincubation and at no time reached the level of inhibition attained by either of the sex hormones alone. Both estradiol and progesterone at pharmacologic levels significantly inhibited beta-glucuronidase and lysozyme release, whereas dexamethasone did not inhibit degranulation despite prolonged preincubation. Neutrophils isolated from women during various phases of the menstrual cycle and during the third trimester of pregnancy did not differ with respect to chemotactic peptide-stimulated O2- generation. These data suggest that inhibition of neutrophil responses requires the continuous presence of pharmacologic levels of estradiol and progesterone.

Dose-Response Relationship, Drug↗
PubMed1984

Generation of C5-derived peptides and other immune reactants in the sera of patients with systemic lupus erythematosus.

Activated complement components and immune complexes cause neutrophil aggregation in vitro and in vivo. We have previously demonstrated that sera of patients with active systemic lupus erythematosus (SLE) provoke the aggregation of normal neutrophils in vitro. In this study the serum or plasma of 4 such patients was fractionated on Sephadex G-75. In 3 patients neutrophil aggregating activity (NAA) was detectable in fractions which coeluted with reference C5-derived peptides (estimated molecular radius of 17,000). The activity of these fractions was inhibitable by antibodies to human C5. All patients also had activity that coeluted with reference immune complexes. In addition, material of apparent molecular radius under 12,000 that contributed to the neutrophil aggregating activity of SLE sera was detected. In separate experiments increased levels of C5a desarg were demonstrated during active disease by means of radioimmunoassay. These findings suggest that multiple neutrophil aggregants circulate during the course of active SLE. The formation of intravascular leukoaggregates may contribute to endothelial injury in this disease.

Antigen-Antibody Complex↗
PubMed1984

Mechanisms of mediator release from neutrophils.

The encounter of neutrophils with immune complexes and complement components - in the bulk phase or on a surface - leads to their secretion of lysosomal hydrolases, especially neutral proteases, which provoke tissue injury. Secretion of lysosomal enzymes and generation of reactive oxygen species (e.g., O2-. generation are stimulus-specific and can be dissected to establish cause and effect relationships by means of: a) kinetic analysis, b) variations in the stimulus, and c) use of impermeant reagents to block discrete responses. Neutrophils also generate products of 11-cyclooxygenase (e.g., PGE2, TxA2) and of the 5- and 15-lipoxygenases (mono-, di-, and tri-HETEs, LTB4, and their isomers). But the cyclooxygenase products (save TxA2) are not phlogistic by themselves: they inhibit the functions of neutrophils, platelets, macrophages, and mast cells. The most potent pro-inflammatory agent yet identified as a product of arachidonate is LTB4. LTB4 is a potent Ca ionophore, constricts airways, is a potent chemoattractant, and induces local inflammation.

Alprostadil↗
PubMed1984

Rheumatoid arthritis. The role of neutrophil activation.

Neutrophils constitute over 90% of cells found in the synovial fluid of rheumatoid arthritis (RA) patients. Since such fluids also contain immune complexes (IgG-IgG and IgG-IgM rheumatoid factors) and complement split products (C5, C5A, DES, ARG, C3B, etc.), all of the reactants are present for a local Arthus lesion. Moreover, neutrophils from RA patients endocytose these immune complexes and complement components in vivo and in vitro. In consequence, it has been suggested that lysosomal enzymes and other mediators of inflammation released by neutrophils after uptake of immune complexes (in the bulk phase or on the surface) account, at least in part, for rheumatoid inflammation. Secretion of lysosomal hydrolases, especially neutral proteases, which provoke tissue injury and generation of reactive oxygen species (e.g. O2) is part of a stimulus-secretion response to a variety of secretagogues, including immune complexes and complement components. However, the pathways of secretion and O2 generation are stimulus-specific and can be dissected to establish cause and effect relationships by (a) kinetic analysis, (b) varying the stimulus, (c) use of impermeant reagents to block discrete responses. Neutrophils also generate products of 11-cyclo-oxygenase (e.g., PGE2, TXA2) and of the 5- and 15-lipoxygenase (mono-, di and tri-hetes, LTB4 and their isomers). However, the cyclo-oxygenase products (except TXA2) do not cause inflammation acting alone; indeed, they inhibit the function of neutrophils, platelets, macrophages and mast cells. The most potent proinflammatory agent yet identified as a product of arachidonate is LTB4. LTB4 is a potent Ca ionophore, a strong chemo-attractant, induces local inflammation, and activates neutrophils.

Arthritis, Rheumatoid↗
PubMed1984

The inactivation of the polymorphonuclear leukocyte by non-steroidal anti-inflammatory drugs.

When human neutrophils (PMNs) are activated by appropriate stimuli, they aggregate, generate superoxide anion (O2-) and secrete lysosomal enzymes. Pre-incubation of PMNs in vitro with the cyclo-oxygenase (COx) inhibitor piroxicam (50 microM) before stimulation with the chemotactic peptide f-met-leu-phe (FMLP, 10(-7)M) inhibited all of these responses. The COx inhibitor ibuprofen inhibited FMLP-induced aggregation and lysozyme secretion, leaving O2- generation unaffected. Binding of 3H-FMLP was inhibited by piroxicam. When the plant lectin concanavalin A (Con-A, 30 micrograms/ml) or the tumor promoter phorbol myristate acetate (PMA, 50 micrograms/ml) was used as a stimulus, ibuprofen had no effect on PMN response, while piroxicam inhibited only O2- generation. To determine whether such inhibition might also occur in vivo, we tested neutrophil aggregation and O2- generation in response to FMLP in 26 normal subjects. These subjects were then administered therapeutic doses of piroxicam (20 mg/day), ibuprofen (2400 mg/day) or indomethacin (100 mg/day), and neutrophil functions were retested after 3 days. Piroxicam inhibited FMLP-induced aggregation by 31% (5.2 cm2/min versus 3.6 cm2/min, P less than 0.004) and O2- generation by 35% (15.8 nmol cytochrome c reduced versus 10.2 nmol, P less than 0.002). Ibuprofen inhibited FMLP-induced aggregation by 44% (5.2 versus 3.0, P less than 0.03) but had no effect on O2- production. Indomethacin inhibited FMLP-induced aggregation (6.4 versus 2.9, P less than 0.01) but had no effect on O2- generation.(ABSTRACT TRUNCATED AT 250 WORDS)

Anti-Inflammatory Agents↗
PubMed1984

Adenosine deaminase is not required for the generation of superoxide anion.

Neutrophils and macrophages generate superoxide anion during the respiratory burst in response to various stimuli, including microorganisms. It has recently been proposed that an important source of superoxide anion during the respiratory burst that stimulates murine macrophages is the sequential metabolism of adenosine via adenosine deaminase and xanthine oxidase to uric acid. Thus, the immunodeficiency state associated with adenosine deaminase deficiency may be caused at least in part by a defect in superoxide anion generation. The ability to generate superoxide anion of stimulated neutrophils isolated from three children with adenosine deaminase deficiency and associated severe combined immunodeficiency was tested. Neutrophils from all three patients were able to generate superoxide anion. One of these generated 19.1 nmol cytochrome c reduced/10(6) cells (normals = 5.3-33.0, mean 18.4 +/- 7.1) while the other two generated low normal levels. Neutrophils from all three children also generated more superoxide anion after addition of exogenous adenosine deaminase. Thus, no evidence to support a role for cellular adenosine deaminase in the release of superoxide anion by stimulated neutrophils was found. Although neutrophils from patients deficient in adenosine deaminase appear to have no inherent defect in the generation of superoxide anion, the abnormally high concentrations of adenosine found in the plasma of these patients could, in vivo, secondarily, inhibit superoxide anion release.

Adenosine↗
PubMed1984

Formation of leukotrienes and hydroxy acids by human neutrophils and platelets exposed to monosodium urate.

Monosodium urate (MSU) crystals stimulate the production of arachidonic acid metabolites by human neutrophils and platelets. Neutrophils exposed to MSU generated leukotriene B (LTB), 6-trans-LTB4, 12-epi-6-trans-LTB4, and 5S, 12S DHETE from endogenous sources of arachidonate. In addition to these metabolites both monohydroxyeicosatetraenoic acids (i.e., 5-HETE) and omega-oxidation products (i.e., 2O -COOH LTB4) were formed by neutrophils exposed to MSU. Addition of exogenous arachidonic acid led to increased formation of each of these metabolites. When neutrophils were treated with colchicine (10 microM), LTB4 but not 5-HETE formation was impaired. (1-14C)Arachidonate-labeled platelets exposed to MSU released (1-14C)-arachidonate, (14C)-12 HETE, (14C)-HHT and (14C)-thromboxane B2. Results indicate that MSU stimulates arachidonic acid metabolism in both human neutrophils and platelets. Moreover, they suggest not only that metabolites of arachidonate may be considered as possible candidates for mediators of inflammation in crystal-associated diseases, but that colchicine blocks the formation of LTB4.

12-Hydroxy-5,8,10,14-eicosatetraenoic Acid↗
PubMed1984

Production of metabolic products of arachidonic acid during cell-cell interactions.

We studied interactions of human platelets and neutrophils with particular reference to the arachidonic acid pathway. Suspensions of [3H]arachidonate-labeled platelets and unlabeled neutrophils were stimulated with ionophore A23187. We detected several radioactive arachidonate metabolites, which are not produced by platelets alone. These included [3H]-labeled leukotriene B4 (LTB4), dihydroxy-eicosatetraeonic acid (DiHETE), and 5-hydroxy-eicosatetraenoic acid (5-HETE). DiHETE was formed when the platelet product [3H]12-HETE was added to ionophore-stimulated neutrophils. In addition, DiHETE was the major metabolite when [3H]5-HETE, a neutrophil arachidonate product, was added to stimulated platelets. We therefore suggest that upon stimulation, platelet-derived arachidonate can serve as precursor for the neutrophil-derived eicosanoids LTB4 and 5-HETE, and the platelet-derived product 12-HETE can be metabolized to DiHETE by stimulated human neutrophils. More recently we have shown that 12-HETE from thrombin-stimulated platelets can also be metabolized to a new product, 12,20-DiHETE, by unstimulated human neutrophils. It would appear that the platelet and neutrophil lipoxygenase pathways take part in cell-cell interactions--an observation that suggests a role for the neutrophils that are present in hemostatic plugs, thrombi, and inflammatory processes.

Arachidonate Lipoxygenases↗