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G Weissmann

Publications and source records attributed to G Weissmann.

At least 127 records · Page 7Linked to original sources
PubMed1984

Loeb and a Gloria.

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History, 20th Century↗
PubMed1984

Neutrophil stimulation: receptor, membrane, and metabolic events.

In the neutrophil, binding of ligands to their appropriate receptors initiates a sequence of events culminating in the physiological responses of aggregation, degranulation, and superoxide anion generation. Calcium has been proposed as a second messenger in the activation sequence of the neutrophil. Increments in cytosolic free calcium are one of the first measurable events subsequent to receptor occupancy, followed by enhanced plasmalemmal permeability to calcium, a process that may serve to enhance the physiological responses. In contrast to calcium, cyclic AMP (cAMP) does not act as a signal in the activation sequence of the neutrophil. Increments in cAMP that are triggered by complete secretagogues may act as an inhibitory feedback mechanism. Protein kinases, both cAMP- and calcium/phospholipid-sensitive enzymes, may play a role in the activation sequence. Phosphorylation of proteins occurs during neutrophil activation. A role for phosphatidylinositol/phosphatidic acid turnover in calcium gating has been proposed. In addition, modulation of phospholipids could serve to activate a protein kinase C. Finally, phospholipids can serve as a source for arachidonic acid, which is metabolized by a 5-lipoxygenase pathway in the neutrophil. Products of this pathway, such as leukotriene B4, may serve to mediate or modulate the activation sequence.

Animals↗
PubMed1984

Production of arachidonic acid lipoxygenase products during platelet-neutrophil 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. This included [3H]-labeled leukotriene B4 (LTB4), dihydroxyeicosatetraenoic acid (DHETE) and 5-hydroxyeicosatetraenoic acid (5-HETE). When the platelet product, [3H]12-HETE, was added to ionophore-stimulated neutrophils, DHETE was formed. In addition, when [3H]5-HETE, a neutrophil arachidonate product, was added to stimulated platelets, DHETE was the major metabolite. We, therefore, suggest that upon stimulation, the platelet derived arachidonate can serve as precursor for the neutrophil-derived eicosanoids LTB4 and 5-HETE and that the platelet-derived product 12-HETE can be metabolized to DHETE by stimulated human neutrophils. It would appear that the platelet and neutrophil lipoxygenase pathways take part in cell-cell interactions - an observation which suggests a role for the neutrophils which are present in hemostatic plugs, thrombi and inflammatory processes.

12-Hydroxy-5,8,10,14-eicosatetraenoic Acid↗
PubMed1983

Adenosine: a physiological modulator of superoxide anion generation by human neutrophils.

The effects of adenosine were studied on human neutrophils with respect to their generation of superoxide anion, degranulation, and aggregation in response to soluble stimuli. Adenosine markedly inhibited superoxide anion generation by neutrophils stimulated with N-formyl methionyl leucyl phenylalanine (FMLP), concanavalin A (Con A), calcium ionophore A23187, and zymosan-treated serum; it inhibited this response to PMA to a far lesser extent. The effects of adenosine were evident at concentrations ranging from 1 to 1,000 microM with maximal inhibition at 100 microM. Cellular uptake of adenosine was not required for adenosine-induced inhibition since inhibition was maintained despite the addition of dipyridamole, which blocks nucleoside uptake. Nor was metabolism of adenosine required, since both deoxycoformycin (DCF) and erythro-9-(2-hydroxy-3-nonyl) adenine did not interfere with adenosine inhibition of superoxide anion generation. The finding that 2-chloroadenosine, which is not metabolized, resembled adenosine in its ability to inhibit superoxide anion generation added further evidence that adenosine metabolism was not required for inhibition of superoxide anion generation by neutrophils. Unexpectedly, endogenously generated adenosine was present in supernatants of neutrophil suspensions at 0.14-0.28 microM. Removal of endogenous adenosine by incubation of neutrophils with exogenous adenosine deaminase (ADA) led to marked enhancement of superoxide anion generation in response to FMLP. Inactivation of ADA with DCF abrogated the enhancement of superoxide anion generation. Thus, the enhancement was not due to a nonspecific effect of added protein. Nor was the enhancement due to the generation of hypoxanthine or inosine by deamination of adenosine, since addition of these compounds did not affect neutrophil function. Adenosine did not significantly affect either aggregation or lysozyme release and only modestly affected beta-glucuronidase release by neutrophils stimulated with FMLP. These data indicate that adenosine (at concentrations that are present in plasma) acting via cell surface receptors is a specific modulator of superoxide anion generation by neutrophils.

2-Chloroadenosine↗
PubMed1983

Changes in phosphatidylinositol and phosphatidic acid in stimulated human neutrophils. Relationship to calcium mobilization, aggregation and superoxide radical generation.

Human neutrophils aggregate and release mediators of inflammation, such as active oxygen species and lysosomal enzymes, when exposed to the chemoattractant, fMet-Leu-Phe, or the tumor promotor, phorbol myristate acetate. In order to 'stage' events which may lead to such neutrophil responses, we determined the temporal relationship between stimulus-induced changes in the endogenous phospholipids phosphatidylinositol (PI) and phosphatidic acid, the mobilization of calcium, and the onset of aggregation and generation of superoxide anion during the initial 2 min of cell activation. Within 5 s after addition of fMet-Leu-Phe (10(-7) M) neutrophils accumulated phosphatidic acid and the levels of PI decreased, as determined by two-dimensional thin-layer chromatography and phosphorus determinations. By 5 s, phosphatidic acid levels rose approximately 3.5-fold and at 15 s the loss of PI exceeded the quantity of phosphatidic acid generated. In response to phorbol myristate acetate (1 microgram/ml), however, changes in PI or phosphatidic acid were not observed until after 60 s. Accumulation of phosphatidic acid in fMet-Leu-Phe-stimulated cells was not inhibited by chelation of extracellular calcium. Neutrophils exposed to either fMet-Leu-Phe or phorbol myristate acetate also showed rapid decrements in fluorescence of cell-associated chlorotetracycline (used as an indirect probe of mobilization of intracellular membrane-associated calcium) and took up 45Ca2+ from the extracellular medium (under 60 s). The results indicate that changes in calcium mobilization, together with the alterations in phospholipid metabolism (under 5 s) anteceded aggregation and the generation of O2-. (10-15 s) induced by fMet-Leu-Phe. In contrast, when neutrophils were exposed to phorbol myristate acetate, changes in PI and phosphatidic acid (over 60 s) were observed after the mobilization of calcium (under 5 s) and the onset of O2-. generation and aggregation (30-35 s).

Calcium↗
PubMed1983

Interaction of liposomes with human leukocytes in whole blood.

The uptake of multilamellar liposomes into human leukocytes in whole blood in vitro was evaluated on the basis of the cellular association of liposomal markers (3H-labelled cholesterol, lipid phase; [14C]inulin, aqueous phase). The entry of liposomes into human blood leukocytes was linear for 60 min and was mediated by a saturable mechanism displaying affinity constants of 0.28 +/- 0.17 and 0.16 +/- 0.05 mM liposomal lipid (means +/- S.E.) for liposomal lipid and aqueous phase markers, respectively. Amicon filtration analysis of incubation mixtures containing blood and liposomes (phosphatidylcholine:dicetyl phosphate:cholesterol, 70:20:10) showed that 34% of [14C]inulin was lost (neither liposome-associated nor cell-associated) after 60 min. By preincorporating sphingomyelin (35 mol%) into multilamellar liposomes, the leakage of the model aqueous phase marker inulin was reduced to 8% after 60 min, thus enhancing the drug carrier potential of liposomes in blood. As a consequence of their interaction with liposomes, the polymorphonuclear leukocytes in whole blood decreased in apparent buoyant density, while maintaining their viability. These results indicate that blood leukocytes in their natural milieu of whole blood are capable of interacting with, and taking up multilamellar liposomes.

Biological Transport, Active↗
PubMed1983

Neutrophil aggregation induced by sera from patients with active systemic lupus erythematosus.

Activated complement components and immune complexes cause neutrophil (PMN) aggregation in vitro and in vivo, as in dialysis-induced neutropenia and adult respiratory distress syndrome. To investigate the possible role of PMN aggregation in systemic lupus erythematosus (SLE), we studied the capacity of 59 sera from 53 patients to induce aggregation of normal PMN in vitro. Neutrophil aggregating activity (NAA) was present in the sera of 26 of 28 patients with active SLE. The mean NAA in this group was significantly greater than that found in 13 patients with inactive SLE, 20 patients with rheumatoid arthritis, and 17 normal controls. In patients with SLE there was a positive correlation between disease severity and the quantitative measure of NAA. NAA did not correlate with serum C3 or C4 nor with the presence or absence of circulating immune complexes. High levels of NAA were particularly characteristic of central nervous system lupus. These data suggest that the formation of intravascular leukoaggregates may contribute to morbidity in SLE.

Adult↗
PubMed1983

Metabolic requirements for maintenance of the chlortetracycline-labeled pool of membrane-bound calcium in human neutrophils.

Human neutrophils labeled with chlortetracycline (CTC), commonly used as a probe of membrane-bound calcium, release lysosomal enzymes and exhibit a rapid decrease in fluorescence when exposed to the chemotactic peptide fMet-Leu-Phe or the lectin Con A. This decrease has been attributed to the release of calcium from a membrane-associated "trigger pool." The nature of this putative pool has been further characterized by examining the effects of various inhibitors on the CTC fluorescence response and lysosomal enzyme release from stimulated neutrophils. These agents included inhibitors of glycolysis (2-deoxyglucose and iodoacetate), an uncoupler of oxidative- phosphorylation (KCN), and a sulfhydryl inhibitor (N-ethylmaleimide). Resting neutrophils labelled with CTC demonstrated an enhanced decay of baseline fluorescence when exposed to 2-deoxyglucose or iodoacetate. This suggested that the pool of membrane-bound calcium labelled by this probe was maintained by glycolytic metabolism. Furthermore, 2-deoxyglucose and iodoacetate inhibited both the stimulated decrease in CTC fluorescence and lysosomal enzyme release induced by fMet-Leu-Phe and Con A in a time-dependent manner. KCN did not inhibit either response to stimulation, but did retard the recovery of CTC fluorescence observed when fMet-Leu-Phe was used as the stimulus. High concentrations of N-ethylmaleimide (100 microM) completely inhibited both the CTC fluorescence response and lysosomal enzyme release almost immediately; low concentrations of N-ethylmaleimide (30 microM) inhibited lysosomal enzyme release in a time-dependent manner without significantly affecting changes in CTC fluorescence. These results are consistent with the hypothesis that CTC serves as a probe of membrane-bound "trigger" calcium, the release of which is dependent upon intact glycolysis and is a requirement for lysosomal enzyme release.

Adult↗
PubMed1983

The neutrophil in rheumatoid arthritis: its role and the inhibition of its activation by nonsteroidal antiinflammatory drugs.

The activation of the polymorphonuclear leukocyte (PMN) in rheumatoid arthritis produces toxic products that include lysosomal enzymes, stable prostaglandins, and leukotrienes and causes the release of superoxide anion. These products produce the inflammatory response, damage cell membranes, and degrade hyaluronic acid. The inhibition of prostaglandin synthetase by NSAIDs does not, by itself, account for their effectiveness in preventing inflammation in rheumatoid arthritis. In vivo and in vitro experiments were conducted to determine if NSAIDs also exert an effect on neutrophil activation. The NSAIDs tested inhibited discrete PMN functions dependent upon the stimulus tested. The antiinflammatory effects of NSAIDs cannot be entirely explained by their inhibition of prostaglandin synthetase and may, in part, be due to other direct effects upon inflammatory cell activation.

Anti-Inflammatory Agents↗
PubMed1983

Activation of the alternative pathway of complement by monosodium urate crystals.

Monosodium urate crystals (MSU) have been shown to activate the alternative pathway of complement in a dose- and time-dependent fashion at 37 degrees C. Activation was maximal upon addition of 10-20 mg/ml monosodium urate crystals to C2-deficient human serum (C2D) or normal human serum containing 5 mM MgEGTA. Immunoelectrophoretic analysis of such treated sera demonstrated cleavage of C3 and factor B. Incubation of highly purified C3 and factor B with 10 mg/ml MSU did not, however, affect their immunoelectrophoretic pattern, suggesting that cleavage of either factor B or C3 in serum requires an intact alternative complement pathway. The fluid-phase control proteins, Factor H and Factor I, were not found to be diminished upon incubation of C2D serum or NHS containing MgEGTA with MSU. Thus activation appeared to be surface dependent and not a consequence of control protein depletion. It was also found, in agreement with earlier observations, that the classical complement pathway is activated, with concomitant depletion of C1 and C4. We conclude that MSU crystals activate both the classical and alternative pathways, and that such activation may participate in the pathogenesis of gouty arthritis.

Complement Activation↗
PubMed1983

Stimulus-response coupling in sponge cell aggregation: Evidence for calcium as an intracellular messenger.

Aggregation of dissociated sponge cells has been proposed as a model for cell-cell recognition mediated by a specific proteoglycan aggregation factor (Microciona aggregation factor). To test whether sponge cells undergo stimulus-response coupling in which intracellular Ca is a messenger, aggregation of mechanically dissociated cells was studied. Changes in light transmission through cell suspensions paralleled aggregation as judged by microscopy. In the presence, but not absence, of Ca (>5 mM) partially purified Microciona aggregation factor aggregated both living and glutaraldehyde-fixed cells. Evidence for a messenger role of Ca was the following: (i) Addition of Ca to Ca-depleted cells induced aggregation that varied with [Ca]. (ii) Addition of Ca ionophores (A23187 and ionomycin) caused aggregation that varied with [Ca] and far exceeded that provoked by Ca alone. Glutaraldehyde-fixed cells did not respond to ionophores with or without Ca. (iii) Calcium antagonists inhibited aggregation. These included inhibitors of the Ca-calmodulin complex (N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide hydrochloride and 1-[bis(p-chlorophenyl)methyl]-3-[2,4-dichloro-beta-(2,4-dichlorobenzyloxyl)phenylethyl]imidazolinium chloride), Ca channel blockers (La, Co, Cd, and verapamil), and three nonsteroidal anti-inflammatory agents (indomethacin, ibuprofen, and piroxicam). Results indicated not only that early events of sponge aggregation can be quantified by continuous recording but that aggregation is not simply due to passive agglutination of inert cells by an extracellular proteoglycan. Rather, sponge cells recognize surface ligands to which they respond by Ca-dependent stimulus-response coupling.

Journal Article↗