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Biomedical subjects

Y Denizot

Publications and source records attributed to Y Denizot.

At least 19 recordsLinked to original sources
PubMed2006

Platelet-activating factor and human meningiomas.

Meningiomas are common primary intracranial tumours. Platelet-activating factor (PAF) is an inflammatory and angiogenic lipid mediator involved in several types of cancer. The presence of PAF receptor (PAF-R) transcripts, the levels of PAF, the phospholipase A2 activity (PLA2, the enzymatic activity implicated in PAF formation) and the PAF acetylhydrolase activity (AHA, the PAF degrading enzyme) were investigated in 49 human meningiomas. PAF-R transcripts, PAF, PLA2 and AHA were detected in meningiomas. However, their levels did not correlate with biological parameters such as the tumour grade, the presence of associated oedema, necrosis, mitotic index as well as intensity of the neovascularization and chronic inflammatory response. In conclusion, PAF is present in meningiomas where it might act on tumour growth by altering the local angiogenic and/or cytokine networks as previously suggested for human breast and colorectal cancer.

1-Alkyl-2-acetylglycerophosphocholine Esterase↗
PubMed2004

Mouse embryonic stem cell sorting for the generation of transgenic mice by sedimentation field-flow fractionation.

Mouse embryonic stem (ES) cells are an important tool for generation of transgenic mice and genetically modified mice. A rapid and efficient separation of ES cells that respects cell integrity, viability, and their developmental potential while also allowing purified ES fraction collection under sterile conditions might be of great interest to facilitate the generation of chimeric animals. In this study, we demonstrated for the first time the effectiveness of a sedimentation field-flow fractionation (SdFFF) cell sorter to provide, with a characteristic DNA content, a purified ES cell fraction and with a high in vivo developmental potential to prepare transgenic mice by generation of chimeras having a high percentage of chimerism.

Animals↗
PubMed2004

Detection of functional platelet-activating factor receptors on leukemic B cells of chronic lymphocytic leukemic patients.

Although platelet-activating factor receptors (PAF-R) are reported on normal B cells, few results are available concerning leukemic ones. We demonstrated functional PAF-R on cell and nuclear surfaces of leukemic B cells of chronic lymphocytic leukemic (CLL) patients. Analysis of 102 patients revealed dramatic differences for their membrane PAF-R expression, a result that might be related to their plasma IL-4 levels. In the light of the potent immunoregulatory role of PAF on B cell physiology, it is suggested that the presence or absence of PAF-R on leukemic B cells may profoundly affect their in vivo behavior.

Aged↗
PubMed2002

Membrane and intracellular platelet-activating factor receptor expression in leukemic blasts of patients with acute myeloid and lymphoid leukemia.

Platelet-activating factor (PAF), a phospholipid mediator with a wide range of actions on mature leukocytes, acts through PAF-receptors (PAF-Rs) on the membranes of responsive cells. No results are available concerning the putative presence of PAF-Rs on leukemic blasts. Using multiparameter flow cytometry, we assessed intracellular and membrane PAF-Rs on blast cells of acute myeloid leukemic (AML) and acute lymphoid leukemic (ALL) patients. Membrane PAF-Rs were documented in 7/15 cases of ALL and 0/28 cases of AML. Putative intracellular PAF-Rs were found in blasts of 8/8 ALL and 13/13 AML patients. Vitamin D(3) and dimethyl sulfoxide that induced the expression of PAF-Rs on the membrane of the human promyelocytic leukemia cell line, HL60, failed to induce their expression on the membranes of CD34(+) AML blasts. The lack of membrane PAF-Rs on the membranes of AML blasts confirms that these receptors represent a marker of mature cells and that their membrane induction is a consequence of cell maturation and differentiation.

Acute Disease↗
PubMed2002

Analysis of three genetic markers in IgA nephropathy patients from a single region.

BACKGROUND: IgA nephropathy (IgA-N) is the most common glomerular disease. Various genetic factors have been suspected to influence the disease, but they never have been studied in the same cohort of patients. METHODS: In 125 IgA-N biopsy-proven cases, we studied by DNA techniques the allele distribution of 3 polymorphic loci: the angiotensin-converting enzyme (ACE) gene, the specific HLA-DQB1 gene and the hs1,2 enhancer of the alpha1 gene of the IgH locus. Patients were classified as progressive and non-progressive based on a creatininemia above 150 microl/ml or/and a deterioration of the clearance greater than 3 ml/min/year. We analyzed the influence of the polymorphism on the development and the progression of the disease. The control group consisted of 83 heathly subjects. RESULTS: The frequency of HLA-DQB1*0602 was decreased in IgA-N patients (3.6% vs 10.2%, Pc = 0.04, RR = 0.36), suggesting a protective effect of this allele for IgA-N. Kaplan-Meyer analysis with the Cox-proportional hazard model revealed a shorter time between diagnosis and renal failure in patients with the B allele for the al gene hs1,2 enhancer (p = 0.04). ACE polymorphism did not influence the development or the progression of the disease. CONCLUSION: Genes controlling the immune response, such as HLA DQB1 and the alpha1 transcriptional enhancer gene, may influence the development and/or the progression of IgA-N nephropathy. Patients who develop an IgA-N nephropathy have a higher risk of severe evolution if they have a profile of high IgA humoral responder.

Adolescent↗
PubMed2001

Differential alterations in plasma colony-stimulating factor concentrations after coronary artery bypass graft surgery with extracorporeal circulation.

To determine whether colony-stimulating factor (CSF) might participate to the inflammatory response after cardiac surgery, plasma concentrations of granulocyte-CSF (G-CSF), macrophage-CSF (M-CSF) and GM-CSF were measured in 31 patients undergoing coronary artery bypass graft (CABG) surgery with extracorporeal circulation (ECC). Plasma G-CSF and M-CSF concentrations increased after weaning of ECC, reached maximum value at the sixth post-operative hour, and remained elevated at the 24th post-operative hour. In contrast, plasma GM-CSF levels did not change. Plasma M-CSF, G-CSF and GM-CSF values were not different whether patients developed post-operative complications or not. In conclusion, M-CSF and G-CSF are produced after CABG surgery despite the use of high aprotinin doses in hope to abrogate the inflammatory response. G-CSF and M-CSF might play a role in the inflammatory process often observed after CABG surgery.

Colony-Stimulating Factors↗
PubMed2001

Polymorphism of the human alpha1 immunoglobulin gene 3' enhancer hs1,2 and its relation to gene expression.

We studied the hs1,2 transcriptional enhancer identified downstream of the human alpha1 gene of the immunoglobulin H (IgH) locus, for which two different allelic configurations (a and b) were previously reported by Southern blotting. By using a polymerase chain reaction (PCR) method we amplified minisatellites within the hs1,2 core enhancer, with variable numbers of tandem repeats (VNTR) defining three 'PCR alleles' alpha1A, alpha1B and alpha1C (including one, two and three repeats, respectively). Five different alpha1 h1,2 genotypes were encountered in a population of 513 donors, representing 13.8, 34.5, 49.7, 1.3 and 0.6% for the AA, BB, AB, AC and BC genotypes, respectively. Luciferase assays showed that increasing the number of minisatellites increased the transcriptional strength of the alpha1 hs1,2 enhancer. Simultaneous determination of Southern blot alleles and VNTR alleles only showed a partial linkage between both types of polymorphism, altogether defining at least six different allelic forms of the 3'alpha1 region. In conclusion, the present study further demonstrates the genetic instability of the 3'alpha region, for which multiple alleles have been generated through inversions and internal deletions and/or duplications. This study also strengthens the hypothesis that the polymorphism at the IgH 3' regulatory region of the alpha1 gene could play a role in the outcome of diseases involving immunoglobulin secretion.

3' Untranslated Regions↗
PubMed2000

Interferon-gamma-induced membrane PAF-receptor expression confers tumor cell susceptibility to NK perforin-dependent lysis.

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.

Adult↗
PubMed2000

Metabolism and effect of platelet-activating factor on the growth of human myeloma cell lines.

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 [3H]PAF and [3H]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 [3H]thymidine incorporation into DNA. As a positive control of PAF effect on myeloma cells, PAF (1 microM) 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.

Cell Division↗
PubMed2000

Effects of lipoxygenase metabolites of arachidonic acid on the growth of human blood CD34(+) progenitors.

The influence of lipoxygenase metabolites of arachidonic acid on proliferation and differentiation of CD34(+) cells was studied. Their effects on the CFU-GM and BFU-E progenitors were investigated by culture of CD34(+) cells in liquid or semisolid medium. Only 12-HETE (1 microM) stimulated the [(3)H]thymidine as well as BrdU incorporation and increased the number of cell divisions (PKH2 tracking). Addition of 12-HETE and 15-HETE but not of LXA(4), LXB(4), LTB(4), and LTC(4) to liquid cultures of CD34(+) cells for 3 and 8 days reduced in a time-dependent manner the number of CFU-GM and BFU-E. Both HETEs also increased the percentage of glycophorin A(+) cells while they reduced the percentage of CD34(-)/CD33(+) cells after 3 and 5 days of liquid cultures. These results show that HETE treatment stimulates proliferation and accelerates the differentiation of CD34(+) cells, mostly toward the erythroid lineage.

12-Hydroxy-5,8,10,14-eicosatetraenoic Acid↗
PubMed2000

Effect of cytokines and lipid mediators on the synthesis of interleukin 1 beta by human bone marrow stromal cells.

This study investigates the production of interleukin (IL-)1beta by cultured human bone marrow stromal cells. RT-PCR experiments indicate that two-thirds of cultures constitutively express IL-1beta mRNA transcripts. Their cell-associated IL-1beta levels are elevated after stimulation with tumour necrosis factor (TNF-)alpha but not with cytokines such as IL-1alpha, IL-3, IL-4, IL-6, IL-7, IL-10, SCF, G-CSF, M-CSF and TGF-beta or lipid mediators such as PGE2, LTB4, LXA4, LXB4, 12-HETE, 15-HETE and PAF. Addition of IL-4, but not IL-10 or TGF-beta, reduces the TNF-alpha-induced cell-associated IL-1beta. IL-1beta is never detected in bone marrow stromal cell supernatants whatever the stimulant added. In conclusion the pro-inflammatory molecule TNF-alpha stimulates bone marrow stromal cell-associated IL-1beta levels while the anti-inflammatory cytokine IL-4 reduces the TNF-alpha-induced effect. These results strengthen the key regulatory role of IL-4 on the production of haematopoietic cytokines by human bone marrow stromal cells.

12-Hydroxy-5,8,10,14-eicosatetraenoic Acid↗
PubMed2000

Effect of cytokines and growth factors on the macrophage colony-stimulating factor secretion by human bone marrow stromal cells.

We have investigated the effect of growth factors, inflammatory and anti-inflammatory cytokines on the macrophage colony-stimulating factor (M-CSF) secretion by cultured human bone marrow stromal cells. Their production of M-CSF cultured in serum-free medium is enhanced in a time-dependent manner in response to tumour necrosis factor (TNF-)alpha and interleukin (IL-)4 but not to IL-1, IL-3, IL-6, IL-7, IL-10, SCF, granulocyte-macrophage colony-stimulating factor (GM-CSF), G-CSF, bFGF and transforming growth factor (TGF-)beta. The co-addition of IL-4 and TNF-alpha has a greater than additive effect on the secretion of M-CSF suggesting that they act synergistically. The anti-inflammatory molecules IL-10 and TGF-beta have no effect on the TNF-alpha-induced M-CSF synthesis by marrow stromal cells. In conclusion TNF-alpha and IL-4 are potent stimulators of the M-CSF synthesis by human bone marrow stromal cells, a result of importance regarding the role of M-CSF in the proliferation/differentiation of mononuclear-phagocytic cells and the role of marrow stromal cells as regulators of marrow haematopoiesis.

Bone Marrow Cells↗
PubMed2000

Plasma interleukin-4, interleukin-10, and interleukin-13 concentrations and complications after coronary artery bypass graft surgery.

OBJECTIVES: To determine whether plasma interleukin (IL)-4, IL-10, and IL-13 concentrations are associated with complications after coronary artery bypass graft (CABG) surgery with cardiopulmonary bypass (CPB). STUDY DESIGN: Prospective descriptive study. SETTING: University teaching hospital. PARTICIPANTS: Thirty-two patients during and 24 hours after CABG surgery. MEASUREMENTS AND MAIN RESULTS: Hemodynamic measurements and blood samples were obtained from 32 patients during and after surgery. Coagulation, pulmonary, and cardiovascular functions were specifically assessed during the first 24 hours postoperatively. Plasma IL-4 and IL-13 levels remained unchanged during CABG surgery. In contrast, plasma IL-10 concentrations increased by 117-fold in the immediate postoperative period and returned to pre-CPB values by 24 hours postoperatively. Plasma IL-10 levels were not different in patients with or without cardiovascular impairment, coagulation disorders, and lung injury. Plasma IL-10 levels did not correlate with the leukocyte count, the amount of catecholamines infused, or the duration of CPB. CONCLUSION: The present results suggest that the development of post-CABG surgery complications might be linked to an insufficient production of anti-inflammatory cytokines, such as IL-4, IL-10, or IL-13, which are unable to counteract the overproduction of inflammatory cytokines.

Aged↗
PubMed2000

Alleles of the alpha1 immunoglobulin gene 3' enhancer control evolution of IgA nephropathy toward renal failure.

BACKGROUND: IgA nephropathy is the most common glomerular disease. Mechanisms leading to its occurrence and controlling the evolution of the disease remain largely unknown. Various genetic factors have been found, mostly implicating immunologically relevant genes (IgH, TCR, human lymphocyte antigen, and complement loci). A regulatory region recently identified downstream, the alpha1 gene of the IgH locus, was a likely candidate for the control of IgA1 production in patients. Alleles of this region, differing by size, sequence, and orientation of the alpha1 hs1,2 transcriptional enhancer, were first identified through Southern blot hybridization. METHODS: We established a polymerase chain reaction (PCR) method suitable for routine testing that amplifies minisatellites within the alpha1 hs1, 2 enhancer, with variable numbers of tandem repeats (VNTR) defining the two alleles. This assay allowed the typing of 104 patients with IgAN and 83 healthy volunteers. Results from typing of alpha1 hs1,2 alleles were compared with long-term clinical outcome in patients. Enhancer alleles were compared in a luciferase reporter gene assay. RESULTS: The alpha1 hs1,2 alleles do not constitute a predictive factor for IgA nephropathy, since similar allelic frequencies were observed in healthy individuals and in unrelated European patients. In contrast, among patients, homozygosity for the weakest enhancer allele (AA genotype) was significantly correlated with a milder form of the disease, whereas the allele B was associated with severe evolution. The minisatellite region within the alpha1 hs1,2 enhancer carried potential transcription factor-binding sites, and its duplication increased the transcriptional strength of the alpha1 hs1, 2 allele B over that of allele A. CONCLUSION: Altogether, these alleles may constitute a risk factor for the prognosis of IgA nephropathy.

3' Untranslated Regions↗