Search PubMed⌕ Search

Biomedical subjects

J Benveniste

Publications and source records attributed to J Benveniste.

At least 37 records · Page 2Linked to original sources
PubMed1994

Regulation of human basophil activation; the role of Na+ and Ca2+ in IL-3-induced potentiation of IgE-mediated histamine release from human basophils.

The release of mediators from human basophils is strongly enhanced by IL-3. However, the signalling pathways of IL-3 are poorly defined in these cells. Since external Ca2+ and Na+ play important regulating roles in histamine release, the possibility that these cations could be involved in the potentiation by IL-3 of the anti-IgE-induced histamine release from human basophils was considered, and it was observed that: (i) IL-3 dramatically decreased the external Ca2+ requirement for IgE-mediated histamine release. However, histamine release from IL-3-treated basophils became only partially independent of external Ca2+, since addition of EGTA in the external medium abolished the effect of IL-3; (ii) decreasing Na+ influx by lowering external Na+ concentration in isosmotic medium inhibited the potentiating effect of IL-3 on IgE-mediated release; (iii) amiloride, an inhibitor of Na+/Ca2+ and Na+/H+ exchanges, and its derivative, benzamil, more specific for Na+/Ca2+ exchanges, inhibited the release potentiated by IL-3. In contrast, the amiloride derivative 5-(N,N-dimethyl)-amiloride, more specific for Na+/H+ exchanges, slightly increased the IL-3-enhanced release. Thus, the decreased requirement for external Ca2+ and the dependence on external Na+, taken with the effect of the Na+/Ca2+ exchange inhibitors, suggest that Na+/Ca2+ exchanges are involved in the IL-3-induced enhancement of IgE-mediated human basophil histamine release.

Amiloride↗
PubMed1994

Anti-IgE induces the opening of non selective cation channels on human basophils.

Basophils play a major role in allergic reactions-particularly in late phase reactions-by releasing histamine and other mediators of inflammation. Although transmembrane ion fluxes are thought to play an important role in the modulation of histamine release, little is known about ion pathways through the basophil membrane. We thus studied human basophils from normal subjects (n = 25 cells) with the patch-clamp method. We observed that IgE-dependent activation of human basophils led to the opening of non selective cation channels with a 20pS conductance. This was obtained when the patch pipette was applied onto the cell surface and sealed onto it in order to measure transmembrane currents on a small surface of intact basophils (cell-attached configuration). Non selective channels with the same 20pS conductance were also observed when a membrane patch was detached from basophil and its inner side placed in a Ca(2+)-containing medium (inside-out configuration). These data are a first contribution of the patch-clamp method in the understanding of ion movements in human basophils.

Antibodies↗
PubMed1993

Immunoregulatory functions of paf-acether. IX. Modulation of apoptosis in an immature T cell line.

We investigated the ability of a phospholipid cytokine, paf-acether to modulate programmed cell death in an immature human T cell line CEM-C12. Paf-acether alone did not cause cell death, but when it was added to CEM-C12 cells in the presence of calcium ionophore, a marked increase in cell mortality and DNA fragmentation was observed compared with calcium ionophore alone. This effect was dose-dependent between 2 and 10 microM paf-acether and specific in that lysophosphatidylcholine had a minimal effect. Thus, in association with another signal, paf modulates apoptotic processes in an immature human T cell line. This may be relevant to intrathymic lymphocyte maturation.

Apoptosis↗
PubMed1993

Human platelets release a paf-acether: acetylhydrolase similar to that in plasma.

Intact washed human platelets aggregated in response to paf-acether (paf) and did not metabolize [3H]paf at concentrations up to 10 nM. However, when platelets were lysed by exposure to pH 9.5, resulting in 37.5 +/- 2.5% (mean +/- SD, n = 3) lactic dehydrogenase (LDH) release, 20.5 +/- 5.7% of the radioactivity was detected as labeled lyso paf and 5.7 +/- 3.1% as labeled alkylacylglycerophosphocholine. When platelets were aggregated with 0.5 IU/mL thrombin or high concentrations of paf (100 nM), they released a part of their acetylhydrolase without releasing LDH. In supernatants obtained from aggregated platelets, 21 +/- 2% or 10 +/- 2% (n = 3), respectively, of the total platelet acetylhydrolase activity was detected vs. none in supernatants of resting cells. The release of acetylhydrolase was concentration- and time-dependent and paralleled the release of PF 4, a marker for alpha-granules. The acetylhydrolase affinity for paf (Km) measured in sonicates of resting and thrombin-activated platelets was 8.3 +/- 1.5 microM vs. 10.6 +/- 1.5 microM, n = 5, n.s. in a "Mann Whitney" test. The latter Km was slightly but significantly different (P < 0.05, n = 5) from that of the thrombin-released acetylhydrolase (7.9 +/- 1.5 microM) and that of the latter was itself different from plasma acetylhydrolase (5.3 +/- 0.5, P < 0.05, n = 5). Addition of plasma (acid-treated to inactivate acetylhydrolase) decreased the Km value of supernatant acetylhydrolase to 6.1 +/- 1.4 microM. All preparations of acetylhydrolase exhibited similar pH requirements and sensitivity to various inhibitors.(ABSTRACT TRUNCATED AT 250 WORDS)

1-Alkyl-2-acetylglycerophosphocholine Esterase↗
PubMed1993

Inhibition by cardiolipins of platelet-activating factor-induced rabbit platelet activation.

Evidence is presented that cardiolipin, a naturally occurring phospholipid, inhibits the aggregatory effect of platelet-activating factor (paf) on rabbit platelets in vitro. Bovine heart cardiolipin was shown to inhibit the aggregation of washed rabbit platelets induced by 1 x 10(-10) M and 2 x 10(-10) M paf with IC50 values (doses for half-maximal inhibition) of 8.4 +/- 0.8 x 10(-7) M and 2.6 +/- 0.6 x 10(-6) M, respectively. Phosphonocardiolipin was also able to inhibit platelet aggregation induced by 1 x 10(-10) M paf with an IC50 value of 3 +/- 1 x 10(-7) M. Both compounds, in concentrations up to 1 x 10(-5) M, were unable to aggregate washed rabbit platelets and failed to inhibit the aggregation induced by 0.9 and 1.8 microM adenosine diphosphate or 0.2-1.0 microM arachidonic acid. By contrast, the acetylated derivative of cardiolipin exerted an aggregatory effect on aspirin-treated rabbit platelets in the presence of creatine phosphate/creatine phosphokinase. This aggregation was inhibited by the specific paf antagonists BN 52021 and WEB 2086. Also, platelets treated with acetyl-cardiolipin were insensitive to the aggregatory effect of paf. Phosphatidic acid, phosphatidylglycerol, bis(dipalmitoylglycero)phosphate and their phosphono analogues were totally inactive. Similar data were obtained when platelet-rich plasma was used instead of washed rabbit platelets. Our results support the hypothesis that the effect of cardiolipin is mediated through specific paf receptors that act on the rabbit platelet membrane.

Animals↗
PubMed1993

The effects of Zn2+ on guinea pig isolated heart preparations.

Isolated guinea pig hearts were perfused, by the Langendorff technique, with 30, 15, 7.5, and 1.5 microM Zn2+ in Chenoweth solution. Contractile force, coronary flow, and heart rate were recorded by means of Narco IV Physiograph. Calcium inhibitor (Verapamil 1 microM) and anion inhibitor (DIDS: 0.1, 1, and 5 microM) were used subsequently in the perfusing solutions in order to distinguish some of the possible mechanisms that Zn2+ uses to exert its action on cardiac myocytes. Isomolar to zinc concentration of Pb (II) and Co (II) were used to elucidate whether zinc effects on heart are specific for this metal. All hearts were used to estimate their zinc and calcium content by means of AAS (Atomic Absorption Spectrometry). Our findings suggest that the higher the Zn2+ concentration, the more toxic effects on heart are expressed by rapid reversible contractile force reduction and reversible specific changes of heart rate and flow. Zinc 1.5 microM in the perfusing solution benefits heart performance, but not significantly. Furthermore, the metal exerts specific effects on guinea pig heart, and it is rather possible that these effects on cardiac myocytes are held through cell membrane receptors.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗
PubMed1993

Gastric secretion of platelet activating factor and precursors in healthy humans: effect of pentagastrin.

The release of platelet activating factor (PAF-ACETHER or PAF) and its precursors in the gastric lumen was assessed in 13 normal subjects in basal condition and after stimulation by gastrin. Acid, pepsin, and sialic acid outputs were determined under the same conditions. Gastric juice was collected using a nasogastric tube after overnight fast in basal condition for 60 minutes, then under pentagastrin infusion (6 micrograms/kg/hr for 60 minutes). Platelet activating factor was detected at low concentration in 4/13 subjects under basal condition (mean (SEM) 1.2 (0.6) pg/hr) while high concentrations of lyso platelet activating factor (6.1 (1.8) microgram/hr) and of alkyl-acyl-glycerophosphocholine (AAGPC) (11.5 (3) micrograms/hr) were found in 13 and 11 subjects, respectively. Platelet activating factor was not detected during pentagastrin infusion, while lyso platelet activating factor and alkyl-acyl-glycerophosphocholine were detected in 13 and in 12 subjects, respectively. Compared with the basal condition these platelet activating factor precursors increased significantly (p < 0.001) going up to fivefold baseline (31.8 (6.8) micrograms/hr and 53 (9.3) micrograms/hr respectively) in response to pentagastrin. There was a positive correlation between platelet activating factor precursors and acid or pepsin output but not between platelet activating factor precursors and sialic acid. As sialic acid may be considered an index of mucus glycoprotein degradation, it seems that gastrin stimulation of gastric epithelial cells results in a concomittant secretion of platelet activating factor precursors, acid, and pepsin irrespective of mucus glycoprotein degradation.

Acetylation↗
PubMed1993

Presence of anti-insulin reaginic auto-antibodies of the IgG4 class in insulin-dependent (type I) diabetic patients before insulin therapy.

The autoimmune aetiology of type I diabetes has been well documented. We studied whether anti-insulin anaphylactic antibodies were present on the membrane of basophils from type I diabetics by the toluidine blue method (detecting basophil activation after stimulation by insulin). We observed that basophils of recently diagnosed insulin-dependent diabetic patients (n = 13) were statistically more frequently activated by insulin than basophils from noninsulin-dependent diabetics (p < 0.002, n = 8) or non-diabetic subjects (p < 0.05, n = 9). Basophils from normal donors were passively sensitized with plasma from insulin-dependent diabetics and could then be activated by insulin. This sensitization still occurred when using plasma previously heated to 56 degrees C, indicating that the sensitizing antibodies were not of the IgE class. When basophils from type I diabetics were preincubated with anti-IgG subclasses, only anti-IgG4 monoclonal antibodies inhibited the insulin-induced basophil activation. By contrast, preincubation with blocking concentrations of anti-IgG1-3 antibodies or desensitization of the IgE pathway did not modify basophil activation. These experiments strongly suggest the presence of anti-insulin antibodies of the IgG4 subclass in insulin-dependent diabetics before any insulin administration and provide a simple tool to complement the usual method of detecting auto-antibodies in diabetes.

Adult↗
PubMed1992

Regulation of paf-acether receptor expression in human B cells.

Paf-acether (paf) is a phospholipid cytokine alloted with potent inflammatory and immunoregulatory properties. Recent reports indicated that in human B cell lines, paf modulated both early and late activation events. In our study, we showed that four of six human B cell lines specifically bound [3H]paf irrespective of the stage of differentiation, the presence of EBV genome or cell surface phenotype. Binding was saturated and fit a one receptor model with a dissociation constant ranging from 1 to 6 nM and a number of sites per cell ranging from approximately equal to 4000 in Rjc13 to approximately equal to 30,000 in Raji or IM9. In addition, our data indicate that 1) maximal expression occurred during the log phase growth; 2) paf itself (10-100 nM) or rIL-4 (100 U/ml) up-regulated by two- to threefold the number of paf binding sites without affecting the affinity. Finally, we found that activated normal B lymphocytes exhibited a higher capacity than resting B cells to incorporate and metabolize [3H]paf at 37 degrees C. Resting B lymphocytes lacked specific binding capacity for paf, yet specific paf receptors were induced upon stimulation via Staphylococcus aureus Cowan I or phorbol 12,13 dibutyrate plus ionomycin. These results suggest that B cell activation is a critical event for paf receptor expression and modulation.

B-Lymphocytes↗
PubMed1992

Regulation of human basophil activation. II. Histamine release is potentiated by K+ efflux and inhibited by Na+ influx.

Na+ and K+ are the major extra- and intracellular cations, respectively. We have thus studied the role of these ions on human basophil histamine release by modifying their transmembrane gradients or by increasing membrane ion fluxes using ionophores. 1) When external Na+ (reduced to 4 mM) was replaced by the nonpermeating Na+ substitute N-methyl-D-glucamine, the release of histamine was enhanced in 2 mM Ca2+ (from 37.5 +/- 8.0% in 140 mM Na+ to 68.5 +/- 9.1% in low Na+) and became possible in the presence of low Ca2+ (at 1 microM Ca2+: from 0.6 +/- 0.7% in 140 mM Na+ to 36.2 +/- 8.0% in low Na+); moreover, in low Na+, the release of histamine became partly independent on Ca2+ influx. 2) Increasing the Na+ influx with the cation channel-forming gramicidin D inhibited the release of histamine by 33.2 +/- 13.6% (n = 6) in an external Na(+)-dependent manner. 3) Decreasing K+ efflux using K+ channel blockers (4-aminopyridine, quinine, sparteine) inhibited histamine release in a dose-response manner. 4) The K+ ionophore valinomycin, which increases K+ efflux, slightly enhanced IgE-mediated histamine release when used alone, whereas it potentiated the release of histamine from leukocytes previously treated with 4-aminopyridine by 57.0 +/- 18.6% (n = 7). 5) Decreasing K+ efflux by increasing external K+ inhibited IgE-mediated release in a similar manner as Na+ did. The inhibitory effects of Na+ and high K+ were not additive, thus suggesting that both cations inhibited the release by a common mechanism. In conclusion 1) our data evidence that histamine release from human basophils is inhibited by Na+ influx and potentiated by K+ efflux; 2) they suggest that K+ channels are present on the basophil membrane and that Na+ and K+ fluxes act on histamine release most probably via modulation of membrane potential.

4-Aminopyridine↗
PubMed1992

Induction of high-affinity paf receptor expression during T cell activation.

Activated human T cells via the CD2 or the CD3 pathways exhibited a higher capacity than resting T lymphocytes to incorporate and metabolize [3H]pafacether (paf) at 37 degrees C. Resting T lymphocytes lacked specific binding capacity for paf, yet high-affinity paf receptors (paf-R) were induced on CD3- or CD2-dependent activation. This up-regulation in the number of paf-R became apparent by day 1 of culture, reached a maximum of about 25,000 sites cell by days 4 to 6 and subsequently declined. Interestingly, human recombinant interleukin-2 in a dose-dependent manner prevented the decrease of high-affinity paf-R expression on T cells. By contrast, the receptor affinity was constant throughout the culture period. Thus, paf-R at different stages of T cell activation were indistinguishable with respect to receptor-ligand interaction, and differed only in their number. Together, these data demonstrate that after activation human T cells develop membrane high-affinity paf-binding sites. They also suggest for the first time that expression of the paf-R are coupled to T cell activation and/or differentiation.

Antigens, Differentiation, T-Lymphocyte↗
PubMed1992

Significance and regulation of gastric secretion of platelet-activating factor (PAF-acether) in man.

Platelet-activating factor (PAF) has been implicated in the pathogenesis of acute inflammatory and ulcerative diseases of the upper gastrointestinal tract. In the present study, we compared the gastric output of PAF and its precursors with gastric acid output, in patients with various upper gastrointestinal tract diseases and healthy controls. PAF and precursors were also extracted from gastric biopsies from subjects with chronic gastritis and/or gastric colonization by Helicobacter pylori. Under basal conditions, hourly gastric PAF output increased in esophagitis and erosive gastritis, but not in duodenal ulcer or Zollinger-Ellison syndrome. In the gastric juice of duodenal ulcer patients, PAF output rose after secretin, but in patients with Zollinger-Ellison syndrome, PAF was only detected when gastric acid secretion had been reduced by antisecretory drugs and no concurrent changes were observed in serum gastrin levels. After pentagastrin, patients and controls exhibited a significant decrease in PAF output and a negative correlation was found between PAF and acid outputs (r = -0.57, p < 0.01). When PAF was incubated with gastric juice in vitro, it underwent degradation irrespective of the medium pH. We found no relation between the outputs of PAF and precursors and the severity of gastritis or gastric colonization by H. pylori. Overall, these results suggest that PAF might be released in the stomach by gastric epithelial cells and could be responsible for mucosal injury of the upper gastrointestinal tract.

Adult↗
PubMed1992

PAF-acether and acetylhydrolase in stool of patients with Crohn's disease.

PAF-acether (PAF) is a phospholipid mediator with potent biological effects on the digestive tract. We report the presence of PAF in stool of patients with active Crohn's disease (39.1 +/- 13.5 ng/g of stool, mean +/- SEM, N = 19) and its absence in patients with irritable bowel syndrome with diarrhea and diarrhea with malabsorption. Fecal PAF acetylhydrolase activity was higher (P less than 0.04) in patients with Crohn's disease as compared to patients with irritable bowel syndrome with diarrhea and diarrhea with malabsorption. We also report a solid-phase extraction of fecal PAF using silica minicolumns, which yielded results highly correlated with those obtained with a high-performance liquid chromatography method (r = 0.86, P less than 0.001, N = 16). These findings may allow us to implicate PAF in the onset and perpetuation of digestive tract inflammatory symptoms observed during Crohn's disease. They would warrant to investigate the influence of various therapeutic agents, including PAF antagonists, on fecal PAF levels during inflammatory digestive ailments.

1-Alkyl-2-acetylglycerophosphocholine Esterase↗
PubMed1992

Variations of blood PAF-acether levels during coronary artery surgery.

Extracorporeal circulation (ECC) is associated with thrombocytopenia and transient leukopenia. After ECC and coronary artery bypass graft (CABG) surgery, some patients can develop pulmonary and cardiac dysfunction, which might be related to the release of various mediators such as thromboxane A2, C5a, and C3a anaphylatoxins. The involvement of PAF-acether (PAF), a potent vasoactive thrombocytopenic and leukoneutropenic agent, has not been determined. Therefore, 10 patients were studied during and after CABG. The release of PAF, lipo PAF (PAF bound to blood lipoproteins), and lyso PAF (PAF precursor and metabolite) was measured in blood from the left atrium, radial artery, and pulmonary artery before and after CABG. PAF, lipo PAF, and lyso PAF were also determined during ECC at the entry and exit points of the oxygenator. Hemodynamic parameters, platelet, and leukocyte counts in the pulmonary artery were measured simultaneously. PAF did not increase significantly during ECC; it showed a transitory six-fold increase immediately after CABG in the radial artery (0.18 +/- 0.13 v 1.09 +/- 0.36 ng/mL, P < 0.05), but not in the pulmonary artery (0.10 +/- 0.03 v 0.56 +/- 0.21 ng/mL, P > 0.05). Blood PAF amounts in the radial artery were significantly higher than in the left atrium following ECC (1.09 +/- 0.36 v 0.06 +/- 0.04, P < 0.05), probably indicating PAF production in the heart. No variation of blood lipo PAF and lyso PAF was observed. No correlation was seen between PAF amounts and blood cell count.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Pressure↗
PubMed1992

Regulation of human basophil activation. III. Impairment of the inhibitory effect of Na+ on IgE-mediated histamine release in patients with allergic rhinitis.

We recently observed that external Na+ inhibited the IgE-dependent human basophil histamine release (HR) in normal subjects. In this article we report differences in the Na+ effect on basophil HR between normal subjects (n = 16) and age matched patients with allergic rhinitis (AR) (n = 18). As expected, in vitro anti-IgE-stimulated basophils from the group with AR released greater amounts of histamine than basophils from the normal group. However, removal of external Na+ (and replacement by N-methyl-D-glucamine) abolished this difference between the two groups. HR in the normal group increased to the same high level as that of the group with AR. By contrast, the release of histamine in the group with AR was not further increased by Na+ removal. Although high releasers were more frequent in the group with AR, the absence of effect after Na+ removal was not due to the high basal release level (in the presence of Na+) because no effect after Na+ removal was also observed with medium releasers. These results strongly suggest that increased basophil HR in populations with AR, and possibly in other allergic populations, is linked to a defect in the inhibitory effect of Na+.

Adult↗
PubMed1992

Cystatin C levels in sera of patients with human immunodeficiency virus infection. A new avidin-biotin ELISA assay for its measurement.

A solid-phase enzyme-linked immunosorbent assay (ELISA) for determining human serum cystatin C is described. In 50 normal samples, cystatin C concentration was 1247 +/- 224 micrograms/L (mean +/- SD) which is in agreement with previously reported levels. Serum levels of cystatin C and beta 2-microglobulin (beta 2-M) were investigated in a time-course study during the development of human immunodeficiency virus (HIV) infection. We found a persistent and uniform increase in the beta 2-M concentration (2762 +/- 1239 micrograms/L). In contrast to beta 2-M, on the basis of cystatin C levels, we found two distinct populations, one of which demonstrated an increased concentration (1620 +/- 618 micrograms/L). Interestingly a second group (21% of patients) exhibited an initial significant decrease in cystatin C concentration with a mean value of 377 (range 55-850) micrograms/L, followed by an increase. The biphasic pattern of cystatin C serum, a major cysteine proteinase inhibitor, during the course of HIV infection suggests a possible role for these proteinases (or proteinase inhibitors) in the development of this syndrome.

Adolescent↗
PubMed1992

Variations in blood platelet-activating-factor levels after protamine reversal of heparin in humans.

The potent inflammatory mediator PAF-acether (PAF = platelet-activating factor) can produce the same hemodynamic and hematological effects as protamine infusion. In 10 patients, blood PAF and precursor levels were measured in the left atrium, the pulmonary and the radial artery before and after protamine reversal of heparin during coronary artery bypass graft. Blood PAF level in the left atrium increased 6-fold (17 +/- 12 pg.ml-1 vs 98 +/- 46 pg.ml-1, P = 0.03) after protamine infusion. By contrast, a 4-fold decrease was observed in the pulmonary artery blood (130 +/- 48 pg.ml-1 vs 31 +/- 23 pg.ml-1, P = 0.03) and a 9-fold decrease was noted in the radial artery blood (285 +/- 104 pg.ml-1 vs 31 +/- 15 pg.ml-1, P = 0.01). No cardiovascular impairment was observed but all patients exhibited thrombocytopenia. After protamine, PAF in the left atrium reached lower levels than those observed in the pulmonary and radial artery before protamine infusion. Moreover, no significant correlation was observed between platelet counts and PAF levels. Thus PAF seems not to mediate the platelet drop induced by heparin-protamine complexes. A positive correlation was obtained between leukocyte counts in the pulmonary artery and PAF levels in the left atrium (r = 0.78, P = 0.02). Protamine infusion may stimulate PAF biosynthesis by leukocytes in the lung, on the one hand, and accelerate the disappearance of PAF in the arterial bed, on the other hand.

Coronary Artery Bypass↗