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V Praloran

Publications and source records attributed to V Praloran.

At least 55 records · Page 3Linked to original sources
PubMed1998

The presence in human serum of a circulating soluble leukemia inhibitory factor receptor (sgp190) and its evolution during pregnancy.

The specific binding of leukemia inhibitory factor (LIF) or oncostatin-M (OSM) to transmembrane gp190 or gp130 leads to their oligomerization which is necessary for signal transduction. Although, sgp190 and sgp130 counterparts also exist, their biological significance remains to be determined. Interestingly, sgp190 forms have been identified in large amounts in normal mouse sera but so far not in human sera. During gestation, murine sgp190 increases 20-fold to 30-fold, while sgp190 RNA levels increase mostly in the liver, uterus and placenta. Sandwich ELISAs were used to detect the presence and follow the evolution of LIF concentrations and its sgp190 receptor subunit in the sera of healthy pregnant and non-pregnant women. The LIF concentrations in whole blood of pregnant women were significantly lower than those of non-pregnant women, whereas they returned to these latter values soon after delivery. In 51 non-pregnant women, the mean sgp190 concentration was 4.3 0.3 ng/ml. It rose slowly but steadily, increasing 4-fold from the 4th to th 34th week of amenorrhea, at which time, it accelerated more rapidly until reaching 41 weeks of amenorrhea, 12 times the mean control value. Several hours prior to delivery, the sgp190 concentration dropped sharply before returning to control levels 2 days later. The marked increase of sgp190 measured in pregnant women extends to humans the observation previously made in mice and suggests a pivotal role for this cytokine system not only during implantation and early embryo development but also throughout pregnancy and more specifically in the biological function of placenta.

Adult↗
PubMed1997

Production, metabolism and effect of platelet-activating factor on the growth of the human K562 erythroid cell line.

The human immature K562 erythroid cell line was studied for its capacity to produce and to metabolize the phospholipid molecule platelet-activating factor (PAF). K562 cells produced PAF under calcium ionophore stimulation. Lyso PAF and acetyl-CoA (the acetate donor molecule for the acetylation of lyso PAF into PAF) had no effect on the amounts of PAF produced by ionophore-stimulated cells. The metabolism of PAF and lyso PAF by K562 cells was compared to that of freshly-isolated human bone marrow erythroblasts and blood erythrocytes. K562 cells rapidly metabolized [3H]PAF and [3H]lyso PAF with 1-alkyl analogue of phosphatidylcholine as the major metabolic product. In contrast, blood erythrocytes did not. PAF acetylhydrolase activity levels in K562 cells and bone marrow erythroblasts were similar and higher than in blood erythrocytes. PAF (1-100 nM) stimulated [3H]thymidine incorporation in K562 cells grown in low serum concentration, a non-metabolizable PAF agonist being more potent than PAF to stimulate thymidine incorporation. PAF receptor mRNA was detected in K562 cells by polymerase chain reaction on reverse transcripts. The present study demonstrates that K562 cells produce and metabolize PAF and underlines the putative role of erythroid precursors in the modulation of bone marrow PAF concentrations. The effect of PAF on the growth of K562 cells might be mediated through PAF receptors suggesting a potential role of PAF on the proliferation and functions of human erythroid marrow precursors.

1-Alkyl-2-acetylglycerophosphocholine Esterase↗
PubMed1997

AcSDKP plasma concentrations in patients with solid tumours: comparison of two chemotherapeutic regimens.

The tetrapeptide AcSer-Asp-Lys-Pro (AcSDKP) is a physiological inhibitor of the proliferation of haematopoietic stem cells and progenitors. In Ara-C-treated mice, its plasmatic concentrations decrease while the CFU-S start cycling. Infusion of synthetic AcSDKP (Goralatide) at this time protects them from haematoxicity by blocking early cycling of CFU-S. Both in vitro and in vivo, this effect seems to be optimal in a narrow range of concentrations. Thus, a better knowledge of the kinetics of endogenous AcSDKP during cancer treatment could help to optimize the treatments with Goralatide. AcSDKP plasma levels have been measured by a specific EIA in 14 cancer patients during the two initial monthly 5 day courses of chemotherapy with 5-FU alone administered either by continuous infusions (six patients) or by 1 h daily infusions (eight patients). AcSDKP concentrations did not vary significantly during the first and the second course. Together with our previous results in AML patients treated with high doses chemotherapy (Ara-C and Anthracyclin), our present data suggest that the variations of endogenous AcSDKP in patients are dependent of the type, doses and schedule of chemotherapy.

Adult↗
PubMed1997

Spontaneous and inducible production of leukaemia inhibitory factor by human bone marrow stromal cells.

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.

Bone Marrow Cells↗
PubMed1997

Is treatment with hydroxyurea leukemogenic in patients with essential thrombocythemia? An analysis of three new cases of leukaemic transformation and review of the literature.

From 1981 to 1995, we diagnosed, followed and treated at our institution fifty-eight cases of essential thrombocythemia (ET), using hydroxyurea (HU) as first-line therapy in these patients. Three patients who were continuously receiving HU had a leukemic transformation after a chronic phase of respectively 47, 81 and 90 months. One patient developed an acute leukemia with minimal myeloid differentiation (AML MO) and soon died of refractory disease; the second developed a refractory anemia with excess blasts in transformation (t-RAEB) and survived one year; the third patient developed a chronic myelomonocytic leukemia (CMML) and is alive at 21 months. The two former patients had complex nonrandom bone marrow karyotypic abnormalities, suggestive of therapy-related leukemia, whereas the latter one had a normal karyotype throughout the chronic and leukemic phase. These findings, together with recently published results on myeloproliferative disorders (MPD) treated with HU, suggest that this drug might be as leukemogenic as other myelosuppressive therapies in patients with ET. Longterm HU therapy should be reserved for patients in whom the treatment benefits obviously outweigh the risk of inducing leukemia.

Aged↗
PubMed1997

Thrombocytopenia in the sepsis syndrome: role of hemophagocytosis and macrophage colony-stimulating factor.

BACKGROUND: Thrombocytopenia is frequently encountered in critically ill patients with the sepsis syndrome, but its mechanisms frequently remain undetermined. Hemophagocytosis has been reported as a cause of thrombocytopenia in various diseases. This prospective study was designed to assess: (1) the incidence of hemophagocytosis in patients suffering from both the sepsis syndrome and unexplained thrombocytopenia, and (2) the circulating level of the macrophage-colony-stimulating factor (M-CSF) according to the presence or absence of hemophagocytosis. METHODS: Fifty consecutive patients diagnosed with both the sepsis syndrome and thrombocytopenia of undetermined origin were studied. Hemophagocytosis was diagnosed based on microscopical examination of sternal bone marrow aspiration by two independent observers. Serum M-CSF concentrations were measured in each patient and compared with levels of a normal population (n = 59). Causes and severity of sepsis syndromes as well as serum M-CSF levels were compared between patients with and without hemophagocytosis. RESULTS: Hemophagocytosis was diagnosed in 32 patients (64%). Mean serum M-CSF levels were increased in patients when compared with normal subjects (539 +/- 141 versus 208 +/- 82 IU/mL: P < 0.001), and higher in patients with than without hemophagocytosis (580 +/- 145 versus 457 +/- 89 IU/mL: P = 0.01). Multiorgan dysfunction and infection were independent risk factors of hemophagocytosis (odds ratio = 31.3 and 6.8, 95% confidence interval (CI) = 5.4 to 177.6 and 1.0 to 47.4, P <0.0001 and P = 0.03, respectively). CONCLUSIONS: Hemophagocytosis is a frequent cause of unexplained thrombocytopenia in patients with severe sepsis syndrome. Our results suggest that M-CSF is overproduced in the sepsis syndrome, particularly when hemophagocytosis is present. The role of M-CSF in the initiation and development of hemophagocytosis remains to be determined.

Adult↗
PubMed1997

Production and metabolism of platelet-activating factor by human bone marrow cells.

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↗
PubMed1997

Presence and metabolism of lyso platelet-activating factor in human bone marrow.

Lyso platelet-activating factor (PAF) is the precursor of PAF, an inflammatory phospholipid molecule present in human bone marrow. The present study shows that in healthy volunteers lyso PAF concentrations are significantly lower (P = 0.0001, Mann-Whitney U-test) in bone marrow plasma (594 +/- 67 ng/ml, n = 47) than in blood plasma (1448 +/- 99 ng/ml, n = 31). Marrow plasma lyso PAF concentrations are similar in patients with lymphoid and nonlymphoid malignancies as compared with controls. Freshly isolated mononuclear marrow cells and cultures of marrow stromal cells contain lyso PAF. Experiments with [3H]lyso PAF indicate that human mononuclear bone marrow cells and marrow stromal cells actively acylate lyso PAF into a 1-alkyl analogue of phosphatidylcholine. Results of this investigation indicate: (1) that lyso PAF is present in human marrow cells and plasma; and (2) that marrow cells and stromal cells metabolize it, thus suggesting their role in the regulation of lyso PAF amounts in human bone marrow.

Aged↗
PubMed1997

Effects of lipidic mediators on the growth of human myeloid and erythroid marrow progenitors.

Freshly isolated human marrow mononuclear cells produce lipidic compounds such as PAF and leukotrienes. These lipidic molecules act on human marrow myelopoiesis and erythropoiesis by modulating the growth of committed progenitors (CFU-GM and BFU-E) in vitro. Nanomolar concentrations of leukotriene B4 and C4 stimulate the growth of human marrow CFU-GM. In contrast, micromolar concentrations of lipoxygenase inhibitors (NDGA and BW755C) decrease their growth suggesting a role for endogenous lipoxygenase metabolites in this process. Micromolar concentrations of prostaglandin E2 up-regulate and down-regulate the growth of marrow BFU-E and CFU-GM, respectively. In contrast, the other cyclooxygenase metabolites have no effect. Recent studies indicate that nanomolar concentrations of PAF decrease the growth of CFU-GM and BFU-E from purified marrow CD34+ cells. Together these results indicate that lipidic mediators act on human myelopoiesis and erythropoiesis. However at this time the mechanisms and molecular signals mediating the effects of lipidic molecules on human marrow cells are unexplored.

Bone Marrow↗
PubMed1997

Platelet-activating factor and antagonists modulate DNA synthesis in human bone marrow stromal cell cultures.

Platelet-activating factor (PAF) is present in the human bone marrow. We have investigated the effect of PAF and antagonists (BN 52,021 and CV 3988) on the growth of human marrow stromal cells. PAF (1 microM) stimulates and PAF antagonists (0.1-1 microM) inhibit [3H]thymidine incorporation in cells grown in 5% serum. The catabolism of PAF by stromal cells was inhibited by CV 3988 suggesting the presence of specific PAF receptor on cells. PAF and antagonists (0.1 nM-10 microM) had no effect on cells cultured in high serum concentration (20%) or in low serum concentration (1%) with 0.5 ng/ml of basic fibroblast growth factor (bFGF). This study indicates for the first time that PAF modulates the serum-induced but not the bFGF-induced growth of marrow stromal cells. The interactions between PAF and stromal cells during inflammatory marrow events such as myelofibrosis deserve to be assessed.

1-Alkyl-2-acetylglycerophosphocholine Esterase↗
PubMed1997

Elevated levels of basic fibroblast growth factor in megakaryocytes and platelets from patients with idiopathic myelofibrosis.

Idiopathic myelofibrosis, or agnogenic myeloid metaplasia, is a chronic myeloproliferative disorder characterized by clonal expansion and marrow fibrosis. Although marrow fibrosis appears to be a reactive process, it substantially contributes to impaired haemopoiesis. During the last few years the implication of megakaryocyte-derived growth factors in its pathogenesis has been documented. We previously reported increased expression of TGF-beta in patients with idiopathic myelofibrosis. In the present study we show that circulating megakaryocytic cells from such patients expressed high levels of basic fibroblast growth factor (bFGF). An increased expression of bFGF was also detected in patients' platelets. Under culture conditions, bFGF present in megakaryocytic cells was not exported into the medium. consistent with the fact that bFGF is devoid of a secretion peptide signal. Interestingly, this lack of bFGF secretion was observed in all patients but one, who was in an accelerated phase of the disease and presented an important percentage of circulating megakaryoblasts.

Aged↗
PubMed1997

Cytogenetic study of 30 patients with multiple myeloma: comparison of 3 and 6 day bone marrow cultures stimulated or not with cytokines by using a miniaturized karyotypic method.

Cytogenetics in multiple myeloma (MM) cases are generally difficult to perform due to the low proliferation index of malignant plasma cells (PC) in most cases. Although IL-6 and GM-CSF stimulate the in vitro proliferation of malignant plasma cells, their usefulness for improving cytogenetic results in multiple myeloma patients remains questionable, because results which compare various culture conditions in a sufficient number of patients are not available. By using a miniaturized karyotypic method, we compared in 30 multiple myeloma patients the number and percentage of clonal abnormal mitoses obtained from 3 and 6 d bone marrow cultures performed without or with two combinations of cytokines: IL-6 + GM-CSF or IL-6 + GM-CSF + IL-2 + IL-4 + TNFalpha. The percentage of patients with an abnormal karyotype, which varied with the Durie and Salmon stage of the disease, as well as the type of numerical and structural karyotypic abnormalities that we detected, were in agreement with published results. The detection of clonal karyotypic abnormalities was better after 3d of culture without cytokine than in all other culture conditions. The higher percentage of patients at all stages of MM with an abnormal karyotype in our study (76.6%) than in previous ones (20% to 60%) is largely explained by the large number of mitoses analysed in six different culture conditions due to the use of a miniaturized karyotypic method.

Bone Marrow↗
PubMed1997

Effects of the angiotensin-converting enzyme inhibitor enalapril on blood haematopoietic progenitors and acetyl-N-Ser-Asp-Lys-Pro concentrations.

Acetyl-N-Ser-Asp-Lys-Pro (AcSDKP) is a physiological inhibitor of the proliferation of haematopoietic stem cells. In 12 healthy volunteers treated with the angiotensin-converting enzyme (ACE) inhibitor enalapril (20 mg day-1 for 15 days), we studied plasma and urinary AcSDKP levels, the in vitro degradation of AcSDKP by plasma ACE and the numbers of circulating haematopoietic progenitors (granulocyte-monocytic colony forming unit: CFU-GM; burst forming unit-erythroid: BFU-E; and mixed colony forming unit: CFU-mixed). During treatment, plasma and urinary AcSDKP concentrations increased 2- to 5-fold, degradation of AcSDKP was reduced, and CFU-mixed significantly increased by 100% while BFU-E and CFU-GM significantly decreased by 16% and 26%, respectively. These results indicate that ACE inhibitors may be of value during chemotherapy or radiotherapy, warranting further study.

Adult↗
PubMed1997

Production and consumption of the tetrapeptide AcSDKP, a negative regulator of hematopoietic stem cells, by hematopoietic microenvironmental cells.

This study was performed to evaluate the role of human microenvironmental cells in the metabolism of AcSDKP, a physiological inhibitor of hematopoietic stem cells. Using long-term marrow cultures (LTMCs), whose medium already contained a baseline value of AcSDKP, we found after 2 weeks a net output in the culture supernatant indicating that release by cells from the adherent layer was superior to consumption of the peptide. Since human microenvironmental cells consist of macrophages and vascular smooth-muscle-like stromal cells we generated pure populations of macrophages (by culturing cord blood cells in the presence of granulomonocytic colony-stimulating factor) and of stromal cells (generated by stromal colonies). We found in supernatants of macrophage cultures a significantly (p < 0.01) increased level of AcSDKP (compared with value in medium) while in supernatants of stromal cell cultures the level was decreased. Cell content of angiotensin-converting enzyme (ACE) in stromal cells was higher than in macrophages, which suggests a degradation of AcSDKP by stromal cells because of their higher amount of ACE. Finally, we analyzed the content of AcSDKP in adherent layers of LTMCs (with or without extracellular matrix [ECM] components), macrophages, and stromal cells. We found levels of AcSDKP of 1.5 pMol per 106 cells in extracts from macrophages or from stromal cells. On the contrary, extracts from primary layers of LTMCs contained 3 times more AcSDKP; however, after treatment of primary layers by collagenase, AcSDKP level fell to 1 pMol per 10(6) cells. Immunofluorescence using an anti-AcSDKP monoclonal antibody showed an extracellular network in certain areas of LTMCs. This study shows that 1) macrophages synthesize and release in the supernatant AcSDKP, 2) stromal cells probably degrade the peptide via ACE, and 3) components of the ECM from LTMCs serve as a reservoir for the peptide. These results are reminiscent of what has been described for growth factors, produced by microenvironmental cells, and stored in the ECM in close vicinity to hematopoietic precursors.

Adipose Tissue↗
PubMed1997

Leukemia inhibitory factor concentrations in the bone marrow plasma of healthy subjects and patients with hematologic malignancies.

Several cytokines may play a role in the pathogenesis of various hematopoietic malignancies. As cytokines work locally, we have investigated leukemia inhibitory factor (LIF) concentrations in the bone marrow plasma of healthy subjects and patients with hematopoietic malignancies by using a specific enzyme-linked immunosorbent assay. LIF levels in patient's samples were significantly higher in bone marrow plasmas (330.3 +/- 43.6 pg/ml; n = 29) than LIF levels in blood plasmas (178.9 +/- 16.8 pg/ml; n = 43) (p = 0.0006, Mann-Whitney U-test). Marrow stromal cells which constitutively produce LIF and enhance their synthesis in response to LPS and PMA might be the cell source of the bone marrow-derived LIF. No statistical difference was documented between marrow plasma LIF concentrations of 24 patients with hematological malignancies and healthy controls. At the present time, the role of LIF in the human marrow cytokine network requires further evaluation.

Bone Marrow↗
PubMed1997

Spontaneous and inducible production of macrophage colony-stimulating factor by human bone marrow stromal cells.

Macrophage Colony-Stimulating Factor (M-CSF), which is permanently present in blood and human bone marrow, regulates the proliferation, differentiation and functions of cells of the mononuclear-phagocytic lineage. By using Reverse-Transcriptase Polymerase Chain Reaction (RT-PCR) we demonstrate that human marrow stromal cells express two types of M-CSF transcripts that are translated into the secreted form and the membrane anchored form. By using a specific and sensitive ELISA, we found that the spontaneous production of M-CSF by human marrow stromal cells is enhanced after stimulation with lipopolysaccharide (LPS), phorbol myristic acetate (PMA) and most interestingly by the lipidic mediator of inflammation platelet-activating factor (PAF). Thus, marrow stromal cells might represent a regulated cell source of bone marrow-derived M-CSF. These results not only emphasize the importance of the bone marrow environment in the control of human hematopoiesis but also evidence, for the first time, the potential role of PAF in the marrow cytokine network during inflammatory processes.

Bone Marrow↗