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Biomedical subjects

G Weissmann

Publications and source records attributed to G Weissmann.

At least 91 records · Page 5Linked to original sources
PubMed1986

Phospholipid metabolism in human neutrophils activated by N-formyl-methionyl-leucyl-phenylalanine. Degranulation is not required for release of arachidonic acid: studies with neutrophils and neutrophil-derived cytoplasts.

Neutrophils respond to chemoattractants by aggregating, degranulating, remodelling of phospholipids and releasing arachidonic acid. To determine whether ligand-induced remodelling of phospholipids depends on redistribution of intracellular organelles (degranulation), we compared phospholipid remodelling of human neutrophils with that of neutrophil-derived cytoplasts. Cytoplasts, organelle-depleted vesicles of cytosol surrounded by plasmalemma, cannot degranulate. Without a stimulus, [3H]arachidonate was incorporated preferentially into phosphatidylinositol (PI) and phosphatidylcholine (PC). Exposure of cytoplasts and neutrophils prelabelled with [3H]arachidonate or [14C]glycerol to fMet-Leu-Phe (10(-7) M) induced rapid changes in distribution of label and mass of individual phospholipids: [3H]arachidonate in phosphatidic acid (PA) increased 500% (120 s), [14C]glycerol incorporation and mass of PA approached 200% of unstimulated values, and [3H]arachidonate in PI decreased continuously; these data are compatible with activity of a PI/PA cycle. However, the mass of PI in both preparations and [14C]glycerol label in intact neutrophils increased initially (5 s), suggesting net synthesis and mobilization of more than one pool of PI. Heterogeneity of PC pools was also observed: [3H]arachidonate was lost from PC immediately upon addition of stimulus, whereas mass and [14C]glycerol values increased. Thus, net phospholipid synthesis, redistribution of arachidonate and activation of the PI/PA cycle are immediate responses of the neutrophil to receptor occupancy by chemoattractants. Furthermore, the similarity in response to fMet-Leu-Phe of neutrophils and granule-free cytoplasts indicates that these processes are independent of degranulation.

Arachidonic Acids↗
PubMed1986

Aggregation of marine sponge cells induced by Ca pulses, Ca ionophores, and phorbol esters proceeds in the absence of external Ca.

Cells of the sponge Microciona prolifera dissociated in Ca,Mg-free sea water reaggregate upon addition of Ca, an observation classically attributed to the requirement for Ca of a species-specific aggregation factor. We now report that, unexpectedly, extracellular Ca is not required during aggregation; brief Ca pulses (1-3 sec) terminated by excess EDTA suffice to prepare the cells for aggregation by Ca ionophores (e.g. A23187). We also show that phorbol myristate acetate (PMA) promotes aggregation of pulse-prepared cells. Since PMA and A23187 act synergistically in Microciona, the "twin signal" hypothesis, signalling by Ca and protein kinase C in parallel, is validated in this primitive animal.

Animals↗
PubMed1986

Colchicine inhibits ionophore-induced formation of leukotriene B4 by human neutrophils: the role of microtubules.

Neutrophils which ingest particles (serum-treated zymosan, monosodium urate crystals) or are exposed to calcium ionophore A23187 generate leukotriene B4 (LTB4). Earlier work has shown that cells exposed to colchicine before exposure to monosodium urate crystals produce less LTB4; the formation of 5-HETE is unaffected. To determine whether inhibition by colchicine of LTB4 generation was stimulus-specific and was mediated by microtubule integrity, the effects of colchicine (10 microM, 60 min) on the release of lipoxygenase products from neutrophils exposed to ionophore A23187 (10 microM, 5 min) were examined. In the presence of exogenous arachidonic acid (100 microM, 15 min), colchicine decreased LTB4 to 48% +/- 11.7 of control and 5-HETE to 60.5% +/- 5.7 of control (mean +/- SEM); 15-HETE was also decreased to 61% +/- 10.3 of control. In the absence of exogenous arachidonate, LTB4 was decreased to 22.2% +/- 11.7 of control and 5-HETE to 13% +/- 4.8 of control. Lumicolchicine did not significantly affect formation of 5-HETE or LTB4. However, vinblastine sulfate (20 microM, 60 min), another microtubule-disruptive agent, decreased the formation of both 5-lipoxygenase products. The effects of colchicine and vinblastine were not due to impairment of cell viability because the release of cytoplasmic lactic dehydrogenase was unaffected. Ultrastructural analysis of centriolar microtubules showed that decrements in microtubule numbers of colchicine- and vinblastine-treated cells paralleled decrements in 5-lipoxygenase products. These pharmacologic manipulations suggested that functional microtubules might be required for optimal lipoxygenase activity. Consequently, we prepared neutrophil-derived cytoplasts, devoid of an intact microtubule system. No significant decreases in the 5- or 15-lipoxygenase products were found when cytoplasts were exposed to colchicine in the presence of exogenous arachidonate and A23187. The data show that colchicine inhibits the formation of lipoxygenase products from neutrophils stimulated with A23187, most likely via its effect on microtubules, the integrity of which appears necessary for full expression of 5- and 15-lipoxygenases.

Adult↗
PubMed1986

Leukotriene B4 synthesis and metabolism by neutrophils and granule-free cytoplasts.

Leukotriene B4 [LTB4, (5S,12R)-hydroxyeicosa-6,14-cis-8,10-trans-tetraenoic acid], a potent mediator of inflammation, is released from neutrophils by agonists that provoke degranulation of the cell. To examine whether degranulation is a necessary requirement for synthesis and metabolism of LTB4 (or of other arachidonate metabolites), we prepared neutrophil-derived cytoplasts (neutroplasts), organelle-depleted vesicles of cytoplasm surrounded by the plasma membrane. In the presence of extracellular Ca2+ with or without exogenous arachidonic acid (150 microM), neutroplasts were exposed to the Ca2+ ionophore A23187 (10 microM) and the resultant lipoxygenation products of arachidonate were determined. Neutrophils metabolize arachidonic acid to 5-HETE greater than 15-HETE greater than LTB4 greater than all-trans-LTB4 isomers. Neutroplast products of arachidonate lipoxygenation were 15-HETE greater than 5-HETE greater than LTB4 greater than all-trans-LTB4 isomers. Neutroplasts, like neutrophils, were capable of converting LTB4 into its 20-hydroxy and 20-carboxy metabolites. Finally, neutroplasts could utilize intrinsic arachidonate, since the neutroplasts synthesized LTB4 (30 pmol/mg of protein) in the absence of added arachidonic acid. The data demonstrate that neutrophil degranulation is not required for synthesis or metabolism of LTB4 by neutrophils.

Arachidonic Acid↗
PubMed1986

Complement activation during systemic lupus erythematosus. C3a and C5a anaphylatoxins circulate during exacerbations of disease.

To determine whether activated complement components appear in the circulation of patients with systemic lupus erythematosus (SLE), we measured C5a and C3a by radioimmunoassay. Mean C5a concentration in the plasma of acutely ill SLE patients was 46.0 ng/ml, compared with 17.1 ng/ml in normal controls (P less than 0.01). Mean C3a concentration in patients with severe disease was 526 ng/ml, compared with 134 ng/ml in controls (P less than 0.01). In patients with moderately active SLE, the mean C3a concentration, but not the mean C5a concentration, was also elevated. In addition, C3a was elevated in 15 or 21 patients with active SLE, whereas low levels of C3 or C4 were noted in only 7 of these 21 patients. We conclude that the measurement of complement-derived anaphylatoxins may be useful in the management of patients with SLE. In addition, we suggest that these circulating mediators may contribute to the pathogenesis of vascular injury in patients with the disease.

Complement Activation↗
PubMed1986

Serum complement values (C3 and C4) to differentiate between systemic lupus activity and pre-eclampsia.

It is often difficult to differentiate between an exacerbation of systemic lupus erythematosus (SLE) and intercurrent pre-eclampsia in a patient with SLE since the manifestations of both entities include proteinuria and hypertension. This study was undertaken to determine wether serum C3 and C4 values can help distinguish SLE activity from pre-eclampsia. In 21 nonpregnant women of child-bearing age, the mean C3 level was 124 +/- 5 mg/dl and the mean C4 was 31 +/- 1 mg/dl. In 24 normal women in the third trimester of pregnancy, the C3 and C4 levels were elevated (165 +/- 4 mg/dl, p less than 0.001 versus nonpregnant control women; 37 +/- 2 mg/dl, p less than 0.01 versus nonpregnant control women, respectively). In 17 women in the third trimester of pregnancy with documented pre-eclampsia, the mean C3 level was 162 +/- 4 mg/dl, no different from that in normal pregnant women (p less than 0.001 versus nonpregnant control women; p = NS versus normal pregnant women), and the mean C4 was 29 +/- 3 mg/dl, lower than that found in normal pregnant women (p less than 0.02 versus normal pregnant women). Antinuclear antibody was absent at titers of less than 1:20 in all of these pre-eclamptic patients. In contrast, pregnant women with SLE has significantly lower C3 (103 +/- 13 mg/dl) and C4 (15.3 +/- 3.6 mg/dl) values during the third trimester of pregnancy than either normal pregnant women (p less than 0.001 for C3 and C4) or women with pre-eclampsia (p less than 0.001 for C3 and p less than 0.004 for C4) during the third trimester of pregnancy. Of the eight women with SLE in whom serial complement values were determined, three had falling C3 or C4 levels, and in each, there was a flare of SLE activity either during or immediately after pregnancy. None of the five patients with a rising C3 concentration had a flare of disease activity; however, pre-eclampsia developed in one of these patients, characterized by hypertension and proteinuria. Thus, measurement of serum C3 and C4 can help differentiate between SLE activity and pre-eclampsia, since both C3 and C4 are significantly lower in women with SLE than women with pre-eclampsia, and serum C3 and C4 concentrations rise during uncomplicated or pre-eclamptic pregnancy in women with SLE.

Adult↗
PubMed1986

Synergy between phorbol esters, 1-oleyl-2-acetylglycerol, urushiol, and calcium ionophore in eliciting aggregation of marine sponge cells.

Aggregation of marine sponge cells (Microciona prolifera) resembles stimulus-response coupling of higher organisms in which activation of protein kinase C and movements of intracellular Ca provide twin signals. We now report that activators of protein kinase C (phorbol esters) and ionomycin act synergistically to aggregate sponge cells. Surprisingly--since extracellular Ca is required for integrity of the species-specific aggregation factor--synergistic aggregation proceeded in the complete absence of added extracellular Ca (2.5-20 mM EDTA). The order of activity of phorbol esters and related compounds was that of their effect on protein kinase C (phorbol myristate acetate, phorbol dibutyrate greater than phorbol diacetate much greater than phorbol, 4 alpha-phorbol). 1-Oleyl, 2-acetylglycerol a synthetic activator of protein kinase C, also showed synergy with ionomycin. Phorbol esters and 1-oleyl, 2-acetylglycerol acted in synergy with ionomycin to liberate membrane Ca as detected by decreased fluorescence of chlortetracycline in prelabeled cells. Moreover, urushiol, the toxic principle of poison ivy, but not pentadecanylcatechol, its inert analogue, showed synergy with ionomycin. Synergistic aggregation was inhibited by calmidazolium (10 microM), piroxicam (20-100 microM), and pertussis toxin (20 micrograms/ml). The data not only confirm that marine sponge cell aggregation follows the general sequence of stimulus-response coupling in the cells of higher organisms but also support, in this most ancient of multicellular creatures, the hypothesis that mobilization of intracellular Ca and activation of protein kinase C provide the twin signals for cell activation in the absence of added extracellular Ca.

Animals↗
PubMed1986

Adenosine: an endogenous inhibitor of neutrophil-mediated injury to endothelial cells.

Since adenosine and its analogue 2-chloroadenosine prevent neutrophils from generating superoxide anion in response to chemoattractants, we sought to determine whether these agents could inhibit neutrophil-mediated injury of endothelial cells. The chemoattractant N-formyl-methionyl-leucyl-phenylalanine (FMLP, 0.1 microM) enhanced the adherence of neutrophils to endothelial cells twofold (18 +/- 2% vs. 39 +/- 3% adherence, P less than 0.001) and caused substantial neutrophil-mediated injury to endothelial cells (2 +/- 2% vs. 39 +/- 4% cytotoxicity, P less than 0.001). 2-Chloroadenosine (10 microM) not only inhibited the adherence of stimulated neutrophils by 60% (24 +/- 2% adherence, P less than 0.001) but also diminished the cytotoxicity by 51% (20 +/- 4% cytotoxicity, P less than 0.002). Furthermore, depletion of endogenously released adenosine from the medium by adenosine deaminase-enhanced injury to endothelial cells by stimulated neutrophils (from 39 +/- 4% to 69 +/- 3% cytotoxicity, P less than 0.001). Indeed, in the presence of adenosine deaminase, even unstimulated neutrophils injured endothelial cells (19 +/- 4% vs. 2 +/- 2% cytotoxicity, P less than 0.001). These data indicate that engagement of adenosine receptors prevents both the adhesion of neutrophils and the injury they cause to endothelial cells. Adenosine inhibits injury provoked not only by cells that have been stimulated by chemoattractants but also by unstimulated cells. Based on this model of acute vascular damage we suggest that adenosine is not only a potent vasodilator, but plays the additional role of protecting vascular endothelium from damage by neutrophils.

2-Chloroadenosine↗
PubMed1985

Granules are necessary for death of neutrophils after phagocytosis of crystalline monosodium urate.

Crystalline monosodium urate (MSU) produces inflammation in vivo and kills phagocytes in vitro. A plausible hypothesis to account for crystal-induced cell death is that ingested crystals perforate the phagocytic vacuole into which lysosomes have degranulated: "lysis from within." However, it has also been contended that degranulation is not required for crystal-induced cell death. To resolve this controversy, we have prepared neutrophil-derived cytoplasts ("neutroplasts") which are devoid of most cellular organelles, including lysosomal granules. Both intact neutrophils and neutroplasts ingested MSU crystals, but inhibition of phagocytosis by cytochalasin B reduced crystal-induced death of neutrophils (release of lactate dehydrogenase) from 42% to 16% without altering lysis of neutroplasts (27% with MSU alone and 26% with MSU and cytochalasin B). Moreover, addition of serum, which prevents direct interaction of crystals with the outer plasma membrane, reduced lysis of neutrophils, reducing cell death from 42% to 25%. After 60 min incubation, serum was totally ineffective in reducing neutrophil death but continued to reduce lysis of neutroplasts from 61% to 13%. Thus, the MSU lysed neutroplasts under conditions in which it ruptured membranes of nonphagocytic structures (erythrocytes, liposomes), i.e., in the absence of serum: "lysis from without." These data suggested that death of neutrophils after internalization of MSU requires a component that is lacking in neutroplasts. Granules (lysosomes) are the best candidates for this component, supporting the general validity of the "lysis from within" hypothesis.

Cell Survival↗
PubMed1985

Hyperalgesic pseudothrombophlebitis. New syndrome in male homosexuals.

Five male homosexuals, four of whom had Kaposi's sarcoma, presented with painful swelling of the lower extremity. The overlying skin was erythematous and exquisitely tender. Deep vein thrombosis was strongly suspected in all patients. Venography, however, revealed no evidence of venous occlusion. This condition, which in this report is termed the hyperalgesic pseudothrombophlebitis syndrome, appears to be another unusual manifestation of the acquired immune deficiency syndrome. It should be considered among the entities known to mimic deep vein thrombosis and must be recognized in order to prevent unnecessary anticoagulation in these patients.

Acquired Immunodeficiency Syndrome↗
PubMed1985

Modes of action of aspirin-like drugs.

Current dogma holds that nonsteroidal anti-inflammatory drugs (NSAIDs) act by inhibition of the synthesis and release of prostaglandins. However, NSAIDs also inhibit the activation of neutrophils, which provoke inflammation by releasing products other than prostaglandins. We now report that NSAIDs (e.g., indomethacin, piroxicam) inhibit activation of neutrophils by inflammatory stimuli, such as C5-derived peptides and leukotriene B4, even when cyclooxygenase products generated in suspensions of stimulated neutrophils (prostaglandin E and thromboxanes) are present. Sodium salicylate (3 mM) greatly inhibited aggregation of neutrophils but had no effect on aggregation of platelets or production of thromboxane induced by arachidonate. Sodium salicylate and other NSAIDs also inhibit calcium movements (45Ca uptake, changes in fluorescence of chlortetracycline and quin-2). Aspirin, sodium salicylate, indomethacin, and piroxicam also enhanced the poststimulation increase in intracellular cyclic AMP. NSAIDs therefore inhibit early steps in neutrophil activation as reflected by their capacity to inhibit movements of Ca and to enhance intracellular levels of cyclic AMP.

Anti-Inflammatory Agents↗
PubMed1985

Circulating hydroxy fatty acids in familial Mediterranean fever.

Episodes of fever, serositis, and arthritis in familial Mediterranean fever (FMF) suggested circulating mediators of acute inflammation (e.g., neutrophil activation). The mean serum neutrophil-aggregating activity of 51 FMF patients was 2.5 +/- 0.2 cm2/min, compared to 1.0 +/- 0.1 cm2/min in 20 normal controls (P less than 0.0002). Lipid extracts of FMF sera retained neutrophil-aggregating activity and had UV absorbance peaks at 269 and 279 nm, indicating the presence of lipids with a conjugated triene structure. Chromatography of extracts yielded peaks that were coeluted with reference dihydroxyicosatetraenoic acids, had UV absorbance peaks at 259, 269, and 279 nm, and possessed neutrophil-aggregating activity. The presence of leukotriene B4 was excluded by chromatography following methyl-esterification. Monohydroxy compounds identified in FMF extracts by gas chromatography/mass spectrometry included 5-hydroxyicosatetraenoic acid, and 9- and 13-hydroxyoctadecadienoic acids. Hydroxy acids were present in 19 of 31 FMF sera and absent in extracts of sera from 8 patients with active systemic lupus erythematosus, 7 with fever from infection, and 12 normal controls. The finding of circulating mono- and dihydroxy fatty acids in FMF suggests that defects in the formation or elimination of these compounds might play a role in the pathogenesis of FMF.

Cell Aggregation↗