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Y Denizot

Publications and source records attributed to Y Denizot.

At least 37 records · Page 2Linked to original sources
PubMed2000

Platelet-activating factor acetylhydrolase and haemophagocytosis in the sepsis syndrome.

Sepsis syndrome (SS) is associated with depressed PAF acetylhydrolase, the enzyme responsible for the degradation of platelet activating factor. PAF acetylhydrolase is in a large part produced by macrophages, whose inadequate activation with haemophagocytosis is frequent in patients with SS. The aim of this study was to test the hypothesis that PAF acetylhydrolase levels could be affected in these critically ill patients, because of the large amounts produced by activated macrophages in vitro and in vivo in animal models. The levels of serum PAF acetylhydrolase were assessed in 90 SS patients, who were divided into three groups: patients with (n = 34) or without haemophagocytosis (n = 31), and patients without thrombocytopenia (n = 25) who were used as a control group. The number of organ dysfunctions was matched between patients with haemophagocytosis and controls. Normal reference values were obtained in 59 randomly selected blood donors. Circulating levels of PAF acetylhydrolase were significantly (p = 0.0001) decreased in patients with SS (57+/-3 nmol/ml/min, n = 90) when compared with healthy subjects (69+/-3 nmol/ml/min, n = 59). PAF acetylhydrolase levels were greater in the presence of a haemophagocytosis but without statistical significance (64.2+/-6.5 vs. 50.1+/-2.8:p = 0.25). Despite the fact that macrophagic activation stimulates the in vitro release of PAF acetylhydrolase, no difference was found between patients with or without haemophagocytosis. The mechanism and the role of the PAF acetylhydrolase reduction in SS patients remain to be determined.

1-Alkyl-2-acetylglycerophosphocholine Esterase↗
PubMed2000

Deregulated platelet-activating factor levels and acetylhydrolase activity in patients with idiopathic IgA nephropathy.

BACKGROUND: Platelet-activating factor (PAF) is a phospholipid mediator with potent inflammatory activities. PAF stimulates IgA synthesis by B cells while IgA aggregates enhance PAF production by neutrophils and mesangial cells. These results led us to investigate blood PAF levels and plasma acetylhydrolase (AHA, the PAF catabolic enzyme) activity in patients with idiopathic IgA nephropathy (IgAN). METHODS: PAF and AHA levels were investigated using the platelet aggregation assay and degradation of (3)H-labelled PAF, respectively. The genotype of AHA with regard to the G994-->T mutation in exon 9 was assessed by an allele-specific polymerase chain reaction. RESULTS: Blood PAF levels were significantly (P:=0.003, Mann-Whitney U:-test) elevated in IgAN patients (50.6+/-6.8 pg/ml, n=33) compared with healthy controls (18+/-5 pg/ml, n=18). In contrast, plasma AHA levels were significantly (P:=0.0001, Mann-Whitney U:-test) reduced in patients with IgAN (61+/-2 nmol/ml/min, n=51) compared with healthy controls (78+/-4 nmol/ml/min, n=53). G994-->T transversion in exon 9 of AHA was not found in any of the IgAN patients. CONCLUSION: Elevated circulating levels of PAF in IgAN patients might result from an insufficient AHA probably related to environmental factors rather than genetic ones. The mechanism and the precise role of the PAF/AHA deregulation in IgAN patients remain to be clarified.

1-Alkyl-2-acetylglycerophosphocholine Esterase↗
PubMed1999

Prostaglandin E2 regulates macrophage colony stimulating factor secretion by human bone marrow stromal cells.

Bone marrow stromal cells regulate marrow haematopoiesis by secreting growth factors such as macrophage colony stimulating factor (M-CSF) that regulates the proliferation, differentiation and several functions of cells of the mononuclear-phagocytic lineage. By using a specific ELISA we found that their constitutive secretion of M-CSF is enhanced by tumour necrosis factor-alpha (TNF-alpha). The lipid mediator prostaglandin E2 (PGE2) markedly reduces in a time- and dose-dependent manner the constitutive and TNF-alpha-induced M-CSF synthesis by bone marrow stromal cells. In contrast, other lipid mediators such as 12-HETE, 15-HETE, leukotriene B4, leukotriene C4 and lipoxin A4 have no effect. EP2/EP4 selective agonists (11-deoxy PGE1 and 1-OH PGE1) and EP2 agonist (19-OH PGE2) inhibit M-CSF synthesis by bone marrow stromal cells while an EP1/EP3 agonist (sulprostone) has no effect. Stimulation with PGE2 induces an increase of intracellular cAMP levels in bone marrow stromal cells. cAMP elevating agents (forskolin and cholera toxin) mimic the PGE2-induced inhibition of M-CSF production. In conclusion, PGE2 is a potent regulator of M-CSF production by human bone marrow stromal cells, its effects being mediated via cAMP and PGE receptor EP2/EP4 subtypes.

12-Hydroxy-5,8,10,14-eicosatetraenoic Acid↗
PubMed1999

Incorporation and effect of arachidonic acid on the growth of the human K562 cell line.

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.

Arachidonic Acid↗
PubMed1999

Interleukin-4 (IL-4), but not IL-10, regulates the synthesis of IL-6, IL-8 and leukemia inhibitory factor by human bone marrow stromal cells.

Leukemia inhibitory factor (LIF), interleukin 6 (IL-6) and IL-8 are important regulators of inflammation and hematopoiesis. Human bone marrow stromal cells regulate marrow hematopoiesis by secreting cytokines. By using reverse-transcriptase polymerase chain reaction (RT-PCR), we demonstrate that human bone marrow stromal cells constitutively express LIF, IL-6 and IL-8 transcripts. By using specific ELISAs, we found that their spontaneous productions of LIF, IL-6 and IL-8 are elevated in response to serum and after stimulation with the pro-inflammatory cytokines IL-1alpha and TNF-alpha. The anti-inflammatory cytokine IL-4 reduces their serum- and cytokine-induced LIF secretion. By contrast, IL-4 stimulates their serum- and IL-1alpha-induced IL-6 synthesis. IL-4 has no effect on the serum-induced IL-8 synthesis by marrow stromal cells, but stimulates their cytokine-induced IL-8 production. The anti-inflammatory cytokine IL-10 has no effect on the serum- and cytokine-induced LIF, IL-6 and IL-8 synthesis by bone marrow stromal cells. RT-PCR experiments reveal the presence of IL-4 receptor alpha-chain mRNA and IL-10 receptor mRNA in cultured bone marrow stromal cells. The differential regulation by IL-4 of two related cytokines, such as LIF and IL-6, and the enhanced effect of this 'anti-inflammatory' cytokine on IL-6 and IL-8 synthesis highlight the tightly controlled regulation and the complexity of the cytokine production within the human bone marrow.

Bone Marrow↗
PubMed1999

Expression of platelet-activating factor receptor transcript-1 but not transcript-2 by human bone marrow cells.

The presence of platelet-activating factor receptor (PAF-R) transcripts 1 and 2 was investigated in human bone marrow cells by a reverse transcriptase polymerase chain reaction (RT-PCR) procedure which detected their simultaneous presence. RT-PCR experiments reveal PAF-R transcript 1 (but not 2) in freshly isolated mononuclear marrow cells, CD34+ hematopoietic stem/progenitor cells and cultured marrow stromal cells. For these experiments, the 5637 human bladder carcinoma cell line is used as a positive control for the presence of PAF-R transcripts 1 and 2. Flow cytometry experiments confirm the presence of PAF-R on marrow stromal cells and CD34+ stem/progenitor cells. In conclusion, the expression of PAF-R transcript 1, which mainly exists in circulating leukocytes, is also found in CD34+ stem/progenitor cells and cells of the marrow microenvironment, strengthening the potential role of PAF during marrow hematopoiesis.

Antigens, CD34↗
PubMed1999

Are lipid mediators implicated in the production of pro- and anti-inflammatory cytokines during cardiopulmonary bypass graft with extracorporeal circulation?

In this study the authors assessed the sequential release of lipid mediators (TXB2, PGE2, 6-keto-PGF1alpha, LTB4, LTC4, PAF), pro-inflammatory cytokines (IL-6, IL-8, TNF-alpha) and anti-inflammatory cytokines (IL-4, IL-10) in 17 patients undergoing coronary artery bypass graft (CABG) with extracorporeal circulation (ECC). Time course of appearance of inflammatory mediators revealed the early and transient increase in lipid mediator plasma concentrations (6-keto-PGF1alpha, LTB4, LTC4, PAF) whereas cytokines (IL-6, IL-8, IL-10) were involved only in late pre- and post-operative periods. No variation of TXB2, PGE2, IL-4 and TNF-alpha levels were found. No correlation was documented between the levels of lipid mediators and pro- or anti-inflammatory cytokines suggesting that lipidic compounds are not implicated in the genesis of cytokines which appear much later involved. Despite the common use of high doses of aprotinin (a non-specific enzyme inhibitor) in hope to abrogate the inflammatory response to cardiopulmonary bypass procedure, this study reports the persistent release of several inflammatory compounds that might be involved in the post-CABG multiple organ failure syndromes.

6-Ketoprostaglandin F1 alpha↗
PubMed1999

Lipid mediators modulate the synthesis of interleukin 8 by human bone marrow stromal cells.

Bone marrow stromal cells regulate marrow haematopoiesis by secreting interleukins (IL) such as IL-8. Lipid mediators modulate IL-8 synthesis in numerous cell types. We have investigated the effects of 5 lipid mediators (PAF, PGE(2), LTB(4), 12-HETE and 15-HETE) on the spontaneous and cytokine-induced IL-8 synthesis by human bone marrow stromal cells. By using reverse-transcriptase polymerase chain reaction (RT-PCR) we demonstrate that these cells constitutively express IL-8 transcripts. By using a specific ELISA, we found that the production of IL-8 by marrow stromal cells is enhanced after stimulation with 12-HETE (1 microM) both in serum-free and serum-containing culture medium. LTB(4)(1 microM) enhances IL-8 production only in serum-supplemented medium. PAF, PGE(2)and 15-HETE (1 microM to 0.1 nM) have no effect on the spontaneous and serum-induced production of IL-8 by human bone marrow stromal cells. PGE(2)(1 microM or 10 nM) reduces marrow stromal cell IL-8 synthesis in response to IL-1alpha or TNF-alpha. In contrast, PAF, 12-HETE, 15-HETE and LTB(4)have no effect. In conclusion, various lipid mediators modulate the spontaneous, serum- or cytokine-induced IL-8 synthesis by bone marrow stromal cells, highlighting, for the first time, their potential role in the regulation of IL-8 production within the human bone marrow.

12-Hydroxy-5,8,10,14-eicosatetraenoic Acid↗
PubMed1999

Incorporation and effect of arachidonic acid on the growth of human myeloma cell lines.

The objectives of this work are to investigate the incorporation of arachidonic acid (AA) in the human myeloma cell lines OPM2, U266 and IM9, and to assess the effect of AA and lipoxygenase products of AA on their growth. The kinetics of acylation of [3H]AA indicates that myeloma cells incorporate AA into their membrane phospholipids and triglycerides. PLA2-treatment and base hydrolysis experiments confirm that [3H]AA is incorporated unmodified in U266, IM9 and OPM2 phospholipids, and is linked by an ester bond. Prelabeling-chase experiments indicate no trafficking of labeled AA among the various phospholipid species. Addition of AA and lipoxygenase products of AA (leukotriene B4 and C4, lipoxin A4 and B4, 12- and 15-hydroxyeicosatetraenoic acid) have no effect on U266, IM9 and OPM2 proliferation assessed by [3H]thymidine incorporation into DNA. In conclusion, while human myeloma cells readily incorporate AA in their membrane phospholipids and triglycerides, AA and lipoxygenase products are not important modulators of their proliferation.

12-Hydroxy-5,8,10,14-eicosatetraenoic Acid↗
PubMed1999

Arachidonic acid and freshly isolated human bone marrow mononuclear cells.

Arachidonic acid (AA), a fatty acid found in the human bone marrow plasma, is the precursor of eicosanoids that modulate bone marrow haematopoiesis. To further our understanding of the role of AA in the bone marrow physiology, we have assessed its incorporation in human bone marrow mononuclear cells. Gas chromatography analysis indicates the presence of AA in their fatty acid composition. In bone marrow mononuclear cells, [3H]-AA is incorporated into triglycerides and is later delivered into phospholipids, a result not observed with blood mononuclear cells. Prelabelling-chase experiments indicate a trafficking of labelled AA from phosphatidylcholine to phosphatidylethanolamine. Stimulation of prelabelled bone marrow mononuclear cells with granulocyte-macrophage colony-stimulating factor (GM-CSF) results in the release of a part of the incorporated labelled AA. Finally, exogenous AA (up to 1 microM) has no significant effect on cell growth. In conclusion, human bone marrow mononuclear cells participate to the control of marrow AA concentrations by incorporating AA into phospholipids and triglycerides. In turn, bone marrow mononuclear cells can release AA in response to the potent haematopoietic growth factor GM-CSF.

Arachidonic Acid↗
PubMed1998

Arachidonic acid and human bone marrow stromal cells.

Human bone marrow stromal cells regulate the growth of marrow hematopoietic progenitors by secreting cytokines. Arachidonic acid (AA) is the fatty acid precursor of prostaglandin E2 (PGE2) and leukotriene B4 (LTB4) that modulate the growth of human bone marrow progenitors. We have investigated the incorporation of AA in human bone marrow stromal cell cultures, their production of PGE2 and LTB4 and the effect of AA on their growth. Gas chromatography analysis reveals the presence of AA in the human bone marrow plasma and in bone marrow stromal cell cultures. In stromal cells, [3H]-AA is incorporated into triglycerides and is later delivered into phospholipids. Prelabeling-chase experiments indicate a preferential incorporation of AA into phosphatidylethanolamine and no trafficking of labeled AA between phospholipid species. Bone marrow stromal cells release PGE2 and LTB4 in response to phorbol myristic acetate (PMA) (1 microM) and tumor necrosis factor alpha (TNF-alpha) (10 ng/ml). Exogenous AA (up to 1 microM) has no significant effect on cell growth. In conclusion, human bone marrow stromal cells capt exogenous AA and, thus, may participate to the control of marrow AA concentrations. They may also regulate human marrow hematopoiesis by secreting AA metabolites such as PGE2 and LTB4.

6-Ketoprostaglandin F1 alpha↗
PubMed1998

IL-6 and IL-8 production by human bone marrow stromal cells.

By using a specific enzyme-linked immunosorbent assay, the authors demonstrated that human bone marrow stromal cells produce IL-6 and IL-8. Their synthesis is enhanced in a dose-dependent manner after stimulation with lipopolysaccharide (LPS) and phorbol myristate acetate (PMA). Interleukin 6 (IL-6) and IL-8 production in response to PMA were markedly diminished by the PKC inhibitor staurosporine. IL-6 (10 ng/ml) stimulated IL-8 production with 0% and 10% fetal calf serum (FCS) in the culture medium. In similar conditions, IL-8 (10 ng/ml) enhanced IL-6 production. IL-1 alpha, IL-1 beta, and IL-3, tumour necrosis factor alpha (TNF-alpha), Stem cell factor (SCF) and granulocyte-macrophage colony-stimulating factor (GM-CSF) (at 10 ng/ml) stimulated IL-6 and IL-8 production in 0% and 10% FCS. G-CSF stimulated and IL-4 inhibited IL-8 production in 10% FCS. IL-2, IL-4 and bFGF stimulated IL-6 production in 0% FCS. These results suggest that bone marrow stromal cells might represent a major source for the cytokine-regulated local production of IL-6 and IL-8 inside human bone marrow.

Bone Marrow Cells↗
PubMed1998

Plasma leukaemia inhibitory factor, interleukin 6 and soluble interleukin 6 receptor levels during cardiopulmonary bypass with extracorporeal circulation.

In this study the authors assessed plasma leukaemia inhibitory factor (LIF), interleukin 6 (IL-6) and soluble IL-6 receptor (sIL-6R) concentrations in 28 patients undergoing coronary artery bypass graft (CABG) with extracorporeal circulation (ECC). Plasma IL-6 levels increased during ECC, reaching a 33-fold increase 6 h after surgery as compared to pre-operative values. In contrast, plasma sIL-6R and LIF concentrations did not vary significantly during cardiac surgery. Thus, LIF is not implicated in the haematological changes and in the inflammatory syndrome observed after CABG. Despite the fact that LIF and IL-6 exhibit several common biological activities, the production of these two cytokines is differently regulated during cardiac surgery with ECC. Plasma IL-6 levels increased during cardiac surgery while sIL-6R levels did not changed. These data contrast with the decreased sIL-6R concentrations with concomitantly high IL-6 levels in patients with sepsis syndrome suggesting that inflammatory reactions in sepsis and after cardiopulmonary bypass are triggered by different mechanisms.

Aged↗
PubMed1998

Effects of lipid mediators on the synthesis of leukaemia inhibitory factor and interleukin 6 by human bone marrow stromal cells.

Human bone marrow stromal cells regulate haematopoiesis by releasing cytokines such as leukaemia inhibitory factor (LIF) and interleukin 6 (IL-6). We have investigated the effects of 5 lipid mediators (i.e. 12-HETE, 15-HETE, platelet-activating factor (PAF), LTB4 and prostaglandin E2 (PGE2)) on their LIF and IL-6 synthesis. 12-HETE, 15-HETE and LTB4 (both at 1 microM) stimulate the LIF production by human bone marrow stromal cells grown in 10% fetal calf serum (FCS). In contrast, PAF and PGE2 have no effect. 12-HETE (1 microM) enhances LIF synthesis in serum free medium 7.7-fold and stimulates IL-1 induced LIF production. 12-HETE, 15-HETE, PAF and LTB4 have no effect on the spontaneous, serum- and cytokine-induced IL-6 synthesis by bone marrow stromal cells. In contrast PGE2 significantly stimulates serum-induced IL-6 synthesis. This study reports for the first time that lipid mediators may act on human haematopoiesis by modulating LIF and IL-6 synthesis by bone marrow stromal cells. Particularly, 12-HETE enhances LIF but not IL-6 synthesis. The different regulation of IL-6 and LIF synthesis in response to lipid mediators highlights the complexity of the cytokine regulation into the human bone marrow.

12-Hydroxy-5,8,10,14-eicosatetraenoic Acid↗
PubMed1998

Effect of platelet-activating factor on the growth of human erythroid and myeloid CD34+ progenitors.

We have assessed the effect of platelet-activating factor (PAF), a biologically active phospholipid present in the human marrow, on the growth of human marrow and blood CD34+ progenitors. While the metabolization rate of PAF by CD34+ cells is low (weak acetylhydrolase and acylation processes) it is readily catabolized by the acetylhydrolase activity present in the growth medium (10% fetal calf serum + 10% 5637-conditioned medium). Treatment of marrow CD34+ cells with the non-metabolizable PAF agonist C-PAF (1 nM to 100 nM) immediately before semi-solid culture significantly (P < 0.01) decreased the number of BFU-E but not of CFU-GM colonies. Treatment of marrow or blood CD34+ cells with C-PAF (10-100 nM) for 3 days in liquid medium before semi-solid culture significantly (P < 0.01) decreased the number of BFU-E and CFU-GM colonies. Treatment of blood CD34+ cells with the two PAF receptor antagonists CV 3988 and BN 52021 (1 microM) had no significant effect on the number of BFU-E and CFU-GM colonies suggesting no role of endogenous PAF in these processes. These results show that exogenous PAF downregulates human erythropoiesis and myelopoiesis, a result that might be of importance during inflammatory states.

Antigens, CD34↗