Search

Numerous B-cell lymphomas feature translocations linking oncogenes to different locations in the immunoglobulin heavy chain (IgH) locus. During Burkitt lymphoma (BL), IgH breakpoints for c-myc translocation stand either close to J(H) segments or within switch regions. Transcription, accessibility, and remodeling of the IgH locus are under the control of the 2 potent cis-acting enhancer elements: E(μ) and the 3′ regulatory region (3′RR). To ensure their respective contributions to oncogene deregulation in the context of the endogenous IgH locus, we studied transgenic mice harboring a knock-in of c-myc in various positions of the IgH locus (3′ to J(H) segments, 5′ to C(μ) with E(μ) deletion and C(α)). The observed spectrum of tumors, kinetics of emergence, and transcriptome analysis provide strong evidence that both E(μ) and 3′RR deregulate c-myc and cooperate together to promote B-cell lymphomagenesis. Transgenics mimicking endemic BL (with c-myc placed 3′ to J(H) segments) exhibited the highest rate of B-cell lymphoma emergence, the highest Ki67 index of proliferation, and the highest transcriptomic similarities to human BL. The 3′RR enhancer alone deregulated c-myc and initiated the development of BL-like lymphomas, suggesting that its targeting would be of therapeutic interest to reduce c-myc oncogenicity in vivo.

Perforin is known to display a membranolytic activity on tumor cells. Nevertheless, perforin release during natural killer (NK)–cell activation is not sufficient to induce membrane target-cell damage. On the basis of the ability of perforin to interact with phospholipids containing a choline phosphate headgroup, we identify the platelet-activating factor (PAF) and its membrane receptor as crucial components in tumor cell killing activity of human resting NK cells. We demonstrate for the first time that upon activation, naive NK cells release the choline phosphate–containing lysolipid PAF, which binds to perforin and acts as an agonist on perforin-induced membrane damage. PAF is known to incorporate cell membranes using a specific receptor. Here we show that interferon-γ (IFN–γ) secreted from activated NK cells ends in PAF-receptor expression on perforin-sensitive K562 cells but not on perforin-resistant Daudi cells. In order to prove the capacity of PAF to interact simultaneously with its membrane PAF receptor and with perforin, we successfully co-purified the 3 components in the presence of bridging PAF molecules. The functional activity of this complex was further examined. The aim was to determine whether membrane PAF-receptor expression on tumor cells, driven to express this receptor, could render them sensitive to the perforin lytic pathway. The results confirmed that transfection of the PAF-receptor complementary DNA into major histocompatibility complex class I and Fas-receptor negative tumor cells restored susceptibility to naive NK cells and perforin attack. Failure of IFN-γ to induce membrane PAF receptor constitutes the first described mechanism for tumor cells to resist the perforin lytic pathway.

In this study we have investigated the presence of PAF receptor (PAF-R) on 5 myeloma cell lines (U266, L363, IM9, OPM2 and XG1), their metabolism of PAF and lyso PAF, and the effect of PAF on their growth. All myeloma cell lines express a PAF acetylhydrolase activity and metabolize [ 3 H]PAF and [ 3 H]lyso PAF in 1-alkyl-2-acyl analogue of phosphatidylcholine. Polymerase chain reaction on reverse transcript (RT-PCR) experiments indicate that OPM2, U266, IM9, XG1 and L363 cells express the PAF-R transcript 1 but not the PAF-R transcript 2. Flow cytometry experiments reveal that PAF-R are present on these myeloma cell lines. PAF and the non-metabolizable PAF agonist 1- O -hexadecyl-2- N -methycarbamyl-glycero-3-phosphocholine have no effect on the growth of OPM2, U266, IM9, XG1 and L363 assessed by [ 3 H]thymidine incorporation into DNA. As a positive control of PAF effect on myeloma cells, PAF (1 μM) enhances by 100% the immunoglobulin synthesis by IM9 cells cultured for 48 h. In conclusion the five myeloma cell lines used in this study metabolize PAF through the deacetylation/reacylation pathway. They express membrane PAF-R through the PAF-R mRNA transcript 1 but PAF does not affect their growth.

Platelet-activating factor (PAF) is a phospholipid mediator of inflammation present in the human bone marrow. Freshly isolated human mononuclear bone marrow cells and marrow stromal cell cultures produced PAF under calcium ionophore (2 microM) and LPS (10 micrograms/ml) stimulation. By contrast, M-CSF (1000 U/ml), GM-CSF (100 ng/ml), IL1, IL3, IL6 and stem cell factor (10 ng/ml) did not stimulate PAF production. Marrow stromal cells produced 50-fold more PAF than freshly isolated mononuclear marrow cells, suggesting that stromal cells might be the major source of the human marrow-derived PAF. Mononuclear marrow cells and stromal cell cultures metabolized PAF with 1-alkyl-2-acyl-glycerophosphocholine as the major metabolic product. PMSF and p-BPB decreased the catabolism of PAF by freshly isolated marrow cells, but not by stromal cell cultures. While stromal cells rather than haematopoietic progenitors might be a major source of the human bone-marrow-derived PAF, both cell types metabolize it, suggesting their putative role in the regulation of PAF concentration in the human bone marrow.

Bone marrow fibroblasts regulate hematopoiesis by interacting directly (cell-to-cell contact) with hematopoietic cells and by secreting regulatory molecules (such as GM-CSF, M-CSF, IL6 and LIF) that modulate hematopoiesis either in a positive or a negative manner. Several cytokines (such as bFGF, EGF, PDGF and TGF-beta) affect the growth of human marrow fibroblasts in vitro. Further in vivo studies are still required to clarify the role of marrow fibroblasts and their interactions with hematopoietic progenitors during myelofibrosis and leukemic diseases.

The authors have previously reported that platelet-activating factor (PAF), a phospholipid mediator with potent proinflammatory activities, is produced in the gastric mucosa and stimulates gastric acid secretion in humans and animals. In the present study they used the human gastric tumour cells HGT1 (clone 6) to examine whether PAF production is regulated by neuromediators. PAF was extracted by ethanol and assayed by the washed platelet aggregation test. HGT1 cells produced PAF spontaneously (110 +/- 20 pg 10(6) cells). The addition of vasoactive intestinal peptide (VIP; 10(-9) to 10(-7) mol L(-1)) or of histamine (10(-5) to 10(-3) mol L(-1)) increased PAF production by three- to fivefold, while the addition of carbachol (10(-7) to 10(-4) mol L(-1)) increased PAF production up to sevenfold. PAF production was also increased up to 10- to 13-fold, in a dose- and time-dependent manner, by the addition of calcium and two- to threefold by the addition of phorbol myristate acetate (PMA; 10(-7) to 10(-5) mol L(-1)). However, the addition of dibutyryl cyclic AMP (dBcAMP; 10(-6) to 10(-4) mol L(-1) was without any effect. This is the first report showing PAF production by gastric epithelial cells in response to histamine, VIP and carbachol. Furthermore, the findings are consistent with a central role of calcium in this production. The results of this study, together with those of previous studies from the authors' laboratory, support the hypothesis that PAF is a physiological mediator of gastric acid secretion.

The spleen and thymus of mice were examined for the presence of PAF after injection of 5-fluorouracil (5-FU) (200 mg/kg). A significant increase of the spleen (P = 0.005) and thymus (P < 0.05) PAF concentrations was noted 48 h after 5-FU infusion. PAF levels in thymus are similar to those of controls from days 4 to 14. By contrast, spleen PAF significantly decreased (0.005 < P < 0.03) from days 7 to 14. Conversely, the 5-FU administration did not modify the spleen and plasma acetylhydrolase activity, suggesting that the variations of PAF levels in thymus and spleen were mainly due to differences of local PAF production. Thus, the chemotherapeutic drug 5-FU modulates in vivo PAF production in haematopoietic organs of mice. Considering the effects of PAF in the processes of B- and T-cell proliferation and functions, these results could be of importance for the role of PAF during human cancer therapy and haematopoiesis in vivo.

De nombreux travaux ont rapporte l'action du mediateur lipidique PAF (platelet-activating factor) sur le monocyte qui est une cellule regulatrice clef de la reponse immune. L'ensemble des donnees publiees suggere un role important entre le PAF et le monocyte, non seulement dans la regulation de la reponse immune mais egalement dans la production de cytokines comme l'IL1 et le TNF. Les relations PAF/monocyte sont tres complexes puisqu'elles dependent de la presence de cellules auxiliaires comme les cellules endotheliales vasculaires, de la concentration locale de PAF et d'un stimulus associe, comme les endotoxines bacteriennes. Si les resultats obtenus dans des modeles experimentaux suggerent un role biologique important du PAF dans ses relations avec le monocyte, l'absence de donnees sur les interactions PAF/monocyte in vivo lors de desordres immunohematologiques et le manque de travaux rapportant ses relations avec les facteurs de croissance monocytaires/macrophagiques (M-CSF et GM-CSF) laissent encore subsister de nombreux points d'interrogations sur son veritable role physiologique lors de la regulation de la reponse immune.

Blood platelet-activating factor (PAF) levels are regulated by a plasma PAF acetylhydrolase. We investigated its levels in cancer patients during the course of a 5-day 5-fluorouracil (5-FU) treatment. PAF acetylhydrolase increased in nine patients with daily bolus infusion of 0.4 g 5-FU per m2 of body surface (81.7 +/- 8.7 nmol PAF/min/ml vs. 66.6 +/- 7.0; P0.001 for day 5 as compared to day 1). By contrast PAF acetylhydrolase did not change in seven patients with continuous infusion of 5-FU. The meaning of these results is discussed in respect of the immunoregulatory role of PAF.

HGT cells are a human gastric tumor cell line. Preliminary data have shown that HGT cells incorporate exogenous arachidonic acid (AA) in their membrane lipids. However, we found that HGT cells are unable to produce significant amounts of AA metabolites after stimulation with calcium ionophore A23187. Furthermore, no lipoxygenase activity was detected in crude HGT cell extracts by employing an assay monitoring the in vitro utilization of linoleic acid. The meaning of these results is discussed in respect of the role of eicosanoids during cell proliferation.

HGT cells are a human gastric cell line derived from a tumour of the stomach. We have investigated the effects of lipoxygenase and cyclooxygenase metabolism inhibitors on HGT cell proliferation, on fatty acid composition of HGT cells and on the incorporation and distribution of arachidonic acid (AA) in HGT lipids. The cyclooxygenase inhibitor aspirin and both cyclooxygenase and the lipoxygenase inhibitor BW 755C suppressed cell proliferation in a concentration-dependent manner. The inhibition of HGT proliferation did not result from a modulation of the fatty acid composition of membrane lipid, which was not affected by treatment with the various inhibitors. Inhibitors of AA metabolism did not alter acylation of exogenous AA into HGT cells nor its subsequent distribution in the lipid and phospholipid species. The role of cyclooxygenase eicosanoids in HGT proliferation is discussed.

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, p0.01). 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.

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.

Platelet-activating factor is an endogenous phospholipid produced by a wide variety of inflammatory cells. Platelet-activating factor induces severe pathological changes in various organs and, among numerous potent effects, causes bowel necrosis. Pouchitis is a poorly understood complication of ileoanal pouch anastomosis which occurs in patients who undergo surgery for ulcerative colitis. The aim of this study was to measure ileal or fecal platelet-activating factor and lyso platelet-activating factor contents in normal volunteers (n = 12), in patients with terminal ileostomy (n = 7), and in patients with ileoanal anastomosis (n = 15) (8 patients have pouchitis defined by the presence of ulcerations on the reservoir). Fecal samples were processed and assessed for platelet-activating factor by platelet aggregation assay. The aggregating material was further characterized as platelet-activating factor by the following: inhibition of the platelet aggregation it induced by specific platelet-activating factor receptor antagonist (BN 52021; IHB, Le Plessis Robinson, France); abolition of platelet aggregation after incubation with phospholipase A2 but not with lipase A1; and retention time on high-performance liquid chromatography. Stool platelet-activating factor content (in nanograms per gram of stool, mean +/- 1SD) was significantly increased in patients with pouchitis (22.2 +/- 16 ng/g) compared with patients with normal reservoir (1.59 +/- 0.63 ng/g, P less than 0.01), terminal ileostomy (0.59 +/- 0.43 ng/g, P less than 0.01), and healthy controls (0 +/- 0 ng/g of stool, P less than 0.001). Lyso platelet-activating factor (nanograms per gram of stool) was increased in patients with pouchitis (10,704 +/- 5499 ng/g) compared with patients with normal reservoir (4721 +/- 4549 ng/g of stool, P less than 0.05), terminal ileostomy (3042 +/- 4019 ng/g, P less than 0.02), and healthy volunteers (128 +/- 107 ng/g, P less than 0.001). In patients with ileoanal anastomosis and pouchitis, increased platelet-activating factor production could be implicated in the inflammation and ulcerations observed in the reservoir.

Clinical studies suggest that Helicobacter pylori may play a role in the pathogenesis of gastroduodenal ulcers in man but direct evidence of mucosal injury by this microorganism is still lacking. Paf-acether (paf) causes a number of disorders including ischaemic bowel necrosis and gastroduodenal ulceration. Since paf is produced by Escherichia coli, we investigated whether it could be synthesised by H pylori. Five H pylori isolates were collected from antral biopsy specimens from patients with gastritis and duodenal ulcer and cultured with selective antibiotics. Colonies obtained from both blood agar and brucella broth medium were used. Paf was determined by platelet aggregation assay after ethanolic extraction and subsequent purification by high performance liquid chromatography. Paf was detected in H pylori in blood agar plates (680 (390) pg paf/1 x 10(6) organisms) but not in bacteria cultured on brucella broth medium. Supplementation of the latter medium with lyso paf and acetyl-CoA, two paf precursors present in high amounts in the mammalian intestine, induced paf production in three of five isolates. The platelet aggregating material extracted from H pylori exhibited biological and physiochemical characteristics identical to those of paf released from eukaryotic cells. These findings suggest that H pylori may add to the local production of paf in inflamed gastric mucosa.

Comparison between holoxenic and axenic mice led to the conclusion that the presence of an intestinal microflora produced a decrease in wall paf in conventional mouse caecum, whereas an increase in wall lyso-paf and alkyl-acyl-glycerophosphocholine (A-A-GPC) content was noticed. By contrast, the presence of flora had no significant incidence on wall paf, lyso-paf and A-A-GPC content of conventional mouse jejunum. Thus, the modulation of gut wall phospholipid composition by intestinal microflora is evidenced for the first time.

Haematopoietic organs of rats were examined for the presence of platelet-activating factor (PAF) and acetylhydrolase before and after treatment with 5-fluoro-uracil (5-FU) (200 mg/kg) a chemotherapeutic compound with apoptotic effects. PAF was reported in thymus, spleen and femoral bone marrow of rats with or without 5-FU. Although acetylhydrolase activity in organs was not affected by 5-FU treatment, elevated levels of PAF were observed in thymus and spleen. For the first time PAF is reported in haematopoietic organs of rats, strengtheningin vitrodata suggesting its role in the apoptotic processes in thymus, in the modulation of the immune response, and in the regulation of haematopoiesis.

Perforin is known to display a membranolytic activity on tumor cells. Nevertheless, perforin release during natural killer (NK)-cell activation is not sufficient to induce membrane target-cell damage. On the basis of the ability of perforin to interact with phospholipids containing a choline phosphate headgroup, we identify the platelet-activating factor (PAF) and its membrane receptor as crucial components in tumor cell killing activity of human resting NK cells. We demonstrate for the first time that upon activation, naive NK cells release the choline phosphate-containing lysolipid PAF, which binds to perforin and acts as an agonist on perforin-induced membrane damage. PAF is known to incorporate cell membranes using a specific receptor. Here we show that interferon-gamma (IFN-gamma) secreted from activated NK cells ends in PAF-receptor expression on perforin-sensitive K562 cells but not on perforin-resistant Daudi cells. In order to prove the capacity of PAF to interact simultaneously with its membrane PAF receptor and with perforin, we successfully co-purified the 3 components in the presence of bridging PAF molecules. The functional activity of this complex was further examined. The aim was to determine whether membrane PAF-receptor expression on tumor cells, driven to express this receptor, could render them sensitive to the perforin lytic pathway. The results confirmed that transfection of the PAF-receptor complementary DNA into major histocompatibility complex class I and Fas-receptor negative tumor cells restored susceptibility to naive NK cells and perforin attack. Failure of IFN-gamma to induce membrane PAF receptor constitutes the first described mechanism for tumor cells to resist the perforin lytic pathway.

Lipoxygenase inhibitors reduce the growth of K562 cells (chronic myelogenous human leukaemia blasts) suggesting a role for endogenous lipoxygenase products of arachidonic acid (AA) in their proliferation. The objectives of this work are to investigate the incorporation of AA into K562 cells and to assess the effects of the exogenous addition of AA and lipoxygenase products on their growth. The mechanism of acylation of [3H]-AA indicates that K562 cells incorporate AA into their membrane phospholipids and triglycerides. PLA2-treatment and base hydrolysis experiments confirm that [3H]-AA is incorporated unmodified into K562 phospholipids and is linked by an ester bond. Prelabelling-chase experiments indicate a transfer of labelled AA from phosphatidylcholine to phosphatidylethanolamine. The addition of AA and lipoxygenase products of AA (leukotriene B4 and C4, lipoxin B4, 12-hydroxyeicosatetraenoic acid (12-HETE) and 15-HETE) has no effect on K562 cell proliferation assessed by [3H]thymidine incorporation into DNA. In conclusion, while K562 cells readily incorporate AA into their membrane phospholipids and triglycerides, AA and lipoxygenase products are not important modulators of their proliferation.

Leukaemia inhibitory factor (LIF) acts on the growth and differentiation of haematopoietic cells. By using a specific enzyme-linked immunosorbent assay for human LIF, we demonstrate that human bone marrow stromal cells produce LIF. LIF synthesis is enhanced in a dose-dependent manner after stimulation with lipopolysaccharide (LPS) and phorbol 12-myristate 13-acetate (PMAS). LIF production in response to PMA is PKC-dependent since the two PKC inhibitors sphingosine and staurosporine markedly diminished it. Interleukin 1alpha (IL-1alpha), IL-1beta, IL-3, IL-6, IL-8, tumour necrosis factor (TNF-alpha) and SCF (both at 10 ng/ml) stimulate LIF production. By contrast macrophage colony-stimulating factor (M-CSF), granulocyte (G)-CSF, GM-CSF, basic fibroblast growth factor (bFGF), platelet-activating factor (PAF), protaglandin E2 (PGE2), leukotriene B4 (LTB4), and leukotriene C4 (LTC4) did not. These results suggest that bone marrow stromal cells might represent a major source for the cytokine-regulated local production of LIF inside human bone marrow.

Some of the most potent inflammatory mediators share a lipidic origin. Upon cell activation, the action of lipases on membrane phospholipids produces free fatty acids and the phospholipid backbone. Among the former are eicosanoids (prostaglandins and leukotrienes); among the latter, platelet-activating factor (PAF; Samuelsson et al. 1987; Wallace 1990; Fig. 1). Studies carried out during the past decade demonstrated that PAF induces biological responses detectable at levels as low as 10 fM (Braquet et al. 1987). In 1972, Benveniste et al. reported that a compound originating from sensitized basophils generated aggregation of platelets. After elucidation of the PAF structure, 1-alkyl-2-acetyl-sn-glycero-3-phosphocholine (Fig. 2), numerous fields of research have emerged, and the subsequent results on PAF biological activities profoundly changed the perspective on its action (Braquet et al. 1987; Pinckard et al. 1988). PAF is an endogenous compound synthesized by a wide range of inflammatory cell types. However, non-inflammatory cells also produce PAF, suggesting that it may be a molecule that has been conserved through evolution. This chapter briefly reviews PAF biosynthesis and degradation in eukaryotic and prokaryotic cells, the immunoregulatory actions of PAF, and some of its actions on cells and tissue structures.

Platelet-activating factor (PAF) is a phospholipid mediator with major immunoregulatory activities. Macrophages produce PAF acetylhydrolase activity, which regulates blood PAF concentrations. Macrophage colony-stimulating factor (M-CSF) is involved in the differentiation and functions of cells from the monocytic/macrophagic lineage. We found that murine macrophagic J774 cells metabolized PAF with lyso PAF as the major metabolite product. As in mouse plasma, the metabolism of PAF by J774 cells was not inhibited by PMSF, p-BPB, DTNB and quinacrine, M-CSF (100-5000 U/ml) significantly decreased PAF acetylhydrolase activity of the J774 cell without exhibiting a significant effect on cell growth. Elevated concentrations of M-CSF are found in blood and tissues during inflammatory states. It could be suggested that a decreased PAF catabolism by tissue macrophages in response to M-CSF may induce local elevated PAF concentrations, thus amplifying the inflammatory response.

Human bone marrow stromal cells were studied for their ability to synthesize and to metabolize platelet-activating factor (PAF), a lipidic compound with potent immunoregulatory properties. When stimulated with 2 microM calcium ionophore for 60 minutes, cultures of stromal cells increased their PAF production (3.52 +/- 0.91 ng/1 x 10(6) cells) compared with controls (0.82 +/- 0.13 ng/1 x 10(6) cells). Addition of exogenous lyso PAF (100 nM) and acetyl-CoA (100 microM) during calcium ionophore stimulation did not change the PAF production. The synthesis of PAF was not influenced by the concentration of albumin in the incubation buffer. The PAF from stromal cells exhibited a hexadecyl chain at the sn-1 position of the molecule, as determined by reverse-phase HPLC. While stromal cells contained low amounts of PAF acetylhydrolase activity and did not secrete it in the culture medium, they metabolized exogenous PAF with 1-alkyl-2-acyl-glycero-phosphocholine and neutral lipids as the major metabolic products. The present results are the first to demonstrate the synthesis and metabolism of PAF by human bone marrow stromal cells. These data suggest that they might be a source of the PAF found in the human bone marrow and/or might be important in the regulation of its levels. The role of PAF on the proliferation and functions of human hematopoietic cells deserves investigation.

PAF is a phospholipid mediator of inflammation with stimulates IL-6 production by murine skin fibroblasts. Although PAF is present in human bone marrow, its role in haematopoiesis is unknown. We have assessed whether PAF stimulates IL-6 and TNF-alpha production by human bone marrow stromal cells (mostly fibroblast-like cells). We report that PAF (1 nM to 10 microM) has no effect on the synthesis of IL-6 and TNF-alpha by human bone marrow stromal cells. This difference may be due to the widely accepted concept "tissue-specific fibroblasts". The role of PAF in the regulation of human haematopoiesis remains to be elucidated.

To assess after cardiopulmonary bypass (CPB) the role of paf-acether (paf), a phospholipid mediator whose injection in animal mimics the hemodynamics observed after CPB.Prospective double-blind randomized study.Single institutional university hospital.18 patients scheduled to undergo coronary artery bypass graft.18 patients randomly received a placebo (n = 8) or 120 mg BN52021 (n = 10), a paf-receptor antagonist injected twice just before vascular cannulation and before cross-clamp release.Hemodynamic measurements were performed with a pulmonary artery and a radial artery catheter before and after the first injection of BN52021 or placebo, at the end of CPB, 1, 15, and 30 minutes after protamine infusion, then 6 hours and 24 hours postoperatively. BN52021 infusion, did not affect hemodynamic parameters. After CPB, the pulmonary artery pressures, the cardiac index, and the pulmonary artery occlusion pressures were statistically the same between groups. By contrast, the pulmonary vascular resistances (1.5 +/- 0.5 IU v 4.5 +/- 0.6 IU, p0.05), the right ventricular systolic work index (5.3 +/- 0.91 g m m-2 v 9.37 +/- 1.02 g m m-2, p0.05) and the transpulmonary gradient (4.7 +/- 1.1 mmHg v 12.0 +/- 1.2 mmHg, p0.05) were lower in the BN52021 group as compared with the placebo group. After protamine infusion, these differences between groups disappeared.Because the inotropic and vasodilator therapy and the volume loading were the same between groups, this study suggests that pretreatment with a paf-receptor antagonist improves post-CPB pulmonary resistance. Nevertheless, this beneficial effect is transient without consequences on left ventricular function indices.

Prelabeling-chase experiments with [14C]arachidonic acid in human cancer gastric cells (HGT) indicated a preferential incorporation of arachidonic acid into triglycerides followed by a transfer to phospholipids. This phenomenon was quicker using cells in log phase growth than in quiescent phase and was not linked to modification of HGT membrane fluidity assessed by the fluorescence polarization of the 1,6-diphenyl hexatriene probe. By contrast, growing cells in a medium enriched with oleic or linoleic acids increase plasma membrane fluidity. The importance of the site of arachidonic incorporation in HGT lipid is discussed.

Au cours des dernieres annees, de nombreux travaux ont decrit l'action du PAF (platelet-activating factor) dans la regulation de la reponse immune, et plus particulierement son action sur les lymphocytes T et B. Les donnees publiees suggerent un role du PAF lors de la proliferation lymphocytaire T et B in vitro ainsi que dans le controle de la production d'immunoglobulines par les lymphocytes B. L'action du PAF depend de sa concentration locale, de la cellule cible, du type de signal mitogenique associe et de la presence ou non de cellules comme les monocytes/macrophages. Cependant, aussi bien le faible nombre de travaux portant sur des modeles animaux in vivo que les multiples interactions entre le PAF et les cytokines ne permettent pas encore d'apporter une reponse definitive sur son veritable role physiologique ou physiopathologique in vivo

Generation of platelet activating factor by intestinal mucosal epithelial cells and lamina propria mononuclear cells was evaluated to elucidate the possible role of this mediator in the pathogenesis of inflammatory bowel disease. Epithelial and lamina propria mononuclear cells were isolated from surgical specimens from control, Crohn's disease, and ulcerative colitis patients. Platelet activating factor was extracted from highly purified cell preparations with 80% ethanol after stimulation with and without 0.2 uM calcium ionophore A23187 and was measured by platelet aggregation assay. Both cell types generated platelet activating factor activity and this was generally comparable for epithelial and lamina propria cells. Basal and stimulated platelet activating factor activity of epithelial and lamina propria cells from ulcerative colitis but not Crohn's disease patients was appreciably higher than that of control. Stimulation with calcium ionophore increased appreciably platelet activating factor activity in lamina propria cells from all groups. In contrast, only epithelial cells from ulcerative colitis showed an appreciable increase after calcium ionophore induction. These results suggest that epithelial cells are important contributors to intestinal platelet activating factor generation under normal and inflammatory conditions and that epithelial cells actively play a part in the pathogenesis of ulcerative colitis.

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.

Four out of 23 consecutive patients treated with high-dose Ara-C for lymphomas in our institution developed a strikingly similar syndrome during the perfusion. It was characterized by the onset of fever, diarrhea, shock, pulmonary edema, acute renal failure, metabolic acidosis, weight gain and leukocytosis. Thorough bacteriological screening failed to provide evidence of infection. Sequential biological assays of IL-1, IL-2, TNF and PAF were performed during Ara-C infusion to ten patients, including the four who developed the syndrome. TNF and PAF activity was found in the serum of respectively two and four of the cases, but not in the six controls. As TNF and PAF are thought to be involved in the development of septic shock and adult respiratory distress syndrome, we hypothesize that high-dose Ara-C may be associated with cytokine release.

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, P0.05), but not in the pulmonary artery (0.10 +/- 0.03 v 0.56 +/- 0.21 ng/mL, P0.05). 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, P0.05), 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)