scholarly journals Platelet factor 4 inhibits human megakaryocytopoiesis in vitro

Blood ◽  
1990 ◽  
Vol 75 (6) ◽  
pp. 1234-1239 ◽  
Author(s):  
ZC Han ◽  
L Sensebe ◽  
JF Abgrall ◽  
J Briere
Keyword(s):  
Progenitor Cells ◽  
Colony Formation ◽  
Mononuclear Cells ◽  
Platelet Factor 4 ◽  
Immunoperoxidase Staining ◽  
High Concentration ◽  
Plasma Clot ◽  
Platelet Factor ◽  
Colony Forming Unit

Platelet factor 4 (PF4) is a multifunctional protein specific to platelets, synthesized in megakaryocytes and stored in alpha granules. This report of our work shows that PF4 potently inhibits human megakaryocyte colony formation in vitro. Colony formation by megakaryocyte progenitor cells from normal bone marrows was studied using the plasma clot culture system and indirect immunoperoxidase staining. Nonadherent mononuclear cells were co-cultured with various concentrations (0 to 20 micrograms/mL) of highly purified human PF4. Statistically significant inhibition of three classes of megakaryocyte progenitor cells, the mixed colony forming unit-megakaryocytes (mCFU- MK), the burst forming unit-megakaryocytes (BFU-MK), and the colony forming unit-megakaryocytes (CFU-MK), was seen at a PF4 concentration of 2.5 micrograms/mL or greater. PF4 had no effect on erythroid (BFU-E) and granulocyte/macrophage (CFU-GM) colony formation except at high concentration (5 micrograms/mL for BFU-E and 10 micrograms/mL for CFU- GM). When a concentration of 5 micrograms/mL PF4 was added at various time points during marrow culture, a reduction of megakaryocyte colony formation also occurred. In the presence of PF4 2.5 micrograms or 5 micrograms/mL, the percentage of mature type of colonies was found to be decreased compared with cultures with no added PF4. These data demonstrate that PF4 inhibits both proliferation and maturation of megakaryocyte progenitor cells in vitro and suggest that PF4 may play a role in autoregulating human megakaryocytopoiesis.

scholarly journals Platelet factor 4 inhibits human megakaryocytopoiesis in vitro

Blood ◽  
1990 ◽  
Vol 75 (6) ◽  
pp. 1234-1239 ◽  
Author(s):  
ZC Han ◽  
L Sensebe ◽  
JF Abgrall ◽  
J Briere
Keyword(s):  
Progenitor Cells ◽  
Colony Formation ◽  
Mononuclear Cells ◽  
Platelet Factor 4 ◽  
Immunoperoxidase Staining ◽  
High Concentration ◽  
Plasma Clot ◽  
Platelet Factor ◽  
Colony Forming Unit

Abstract Platelet factor 4 (PF4) is a multifunctional protein specific to platelets, synthesized in megakaryocytes and stored in alpha granules. This report of our work shows that PF4 potently inhibits human megakaryocyte colony formation in vitro. Colony formation by megakaryocyte progenitor cells from normal bone marrows was studied using the plasma clot culture system and indirect immunoperoxidase staining. Nonadherent mononuclear cells were co-cultured with various concentrations (0 to 20 micrograms/mL) of highly purified human PF4. Statistically significant inhibition of three classes of megakaryocyte progenitor cells, the mixed colony forming unit-megakaryocytes (mCFU- MK), the burst forming unit-megakaryocytes (BFU-MK), and the colony forming unit-megakaryocytes (CFU-MK), was seen at a PF4 concentration of 2.5 micrograms/mL or greater. PF4 had no effect on erythroid (BFU-E) and granulocyte/macrophage (CFU-GM) colony formation except at high concentration (5 micrograms/mL for BFU-E and 10 micrograms/mL for CFU- GM). When a concentration of 5 micrograms/mL PF4 was added at various time points during marrow culture, a reduction of megakaryocyte colony formation also occurred. In the presence of PF4 2.5 micrograms or 5 micrograms/mL, the percentage of mature type of colonies was found to be decreased compared with cultures with no added PF4. These data demonstrate that PF4 inhibits both proliferation and maturation of megakaryocyte progenitor cells in vitro and suggest that PF4 may play a role in autoregulating human megakaryocytopoiesis.

scholarly journals New Insights Into the Negative Regulation of Hematopoiesis by Chemokine Platelet Factor 4 and Related Peptides

Blood ◽  
1998 ◽  
Vol 91 (8) ◽  
pp. 2772-2780 ◽  
Author(s):  
Laurence Lecomte-Raclet ◽  
Mònica Alemany ◽  
Anabelle Sequeira-Le Grand ◽  
Jean Amiral ◽  
Gérard Quentin ◽  
...  
Keyword(s):  
Inhibitory Activity ◽  
Significant Inhibition ◽  
Platelet Factor 4 ◽  
Sequence Length ◽  
Functional Domain ◽  
Heparin Binding ◽  
Platelet Factor ◽  
Colony Forming Unit ◽  
Function Relationship

Platelet factor 4 (PF4) has been recognized as an inhibitor of myeloid progenitors. However, the mechanism of action of this chemokine remains poorly understood. The present study was designed to determine its structure/function relationship. A series of peptides overlapping the C-terminal and central regions of PF4 were analyzed in vitro for their action on murine hematopoietic progenitor growth to assess the minimal sequence length required for activity. The peptides p17-58 and p34-58 possessed an increased hematopoietic inhibitory activity when compared with PF4, whereas the shorter peptides p47-58 and p47-70 were equivalent to the native molecule and the peptide p58-70 was inactive. The PF4 functional motif DLQ located in 54-56 was required for the activity of these peptides. The peptide p34-58 impaired to a similar extent the growth of colony-forming unit-megakaryocyte (CFU-MK) as well as burst-forming unit-erythroid (BFU-E) and colony-forming unit–granulocyte-macrophage (CFU-GM), whereas PF4 was more active on CFU-MK. In the experiments using purified murine CD34+ marrow cells, statistically significant inhibition induced by p34-58 was shown at concentrations of 2.2 nmol/L or greater for progenitors of the three lineages, whereas that induced by PF4 was seen at 130 nmol/L for CFU-MK and 650 nmol/L for CFU-GM and BFU-E, indicating that the p34-58 acts directly on hematopoietic progenitors and its activity is approximately 60- to 300-fold higher than PF4. The p34-58, unlike PF4, lacked affinity for heparin and its inhibitory activity could not be abrogated by the addition of heparin. In addition, an antibody recognizing p34-58 neutralized the activity of p34-58 but not whole PF4 molecule. These results demonstrate that PF4 contains a functional domain in its central region, which is independent of the heparin binding properties, and provide evidence for a model of heparin-dependent and independent pathways of PF4 in inhibiting hematopoiesis.

Spontaneous in vitro Megakaryocyte Colony Formation in Primary Thrombocythemia: Relation to Platelet Factor 4 Plasma Level and Beta-Thromboglobulin/Platelet Factor 4 Ratio

1992 ◽  
Vol 87 (3) ◽  
pp. 118-121 ◽  
Author(s):  
Jean-François Abgrall ◽  
Christian Berthou ◽  
Jean-Michel Cauvin ◽  
Claudie Autrand ◽  
Isabelle Renard ◽  
...  
Keyword(s):  
Plasma Level ◽  
Colony Formation ◽  
Platelet Factor 4 ◽  
Platelet Factor ◽  
Primary Thrombocythemia

Megakaryocytic Colony Stimulating Activity A Potential Regulator Of Human Megakaryocytopoiesis

1981 ◽  
Author(s):  
R Hoffman ◽  
E Mazur ◽  
E Bruno ◽  
V Floyd
Keyword(s):  
Bone Marrow ◽  
Aplastic Anemia ◽  
Colony Formation ◽  
Mononuclear Cells ◽  
Growth Media ◽  
Severe Thrombocytopenia ◽  
Serum Samples ◽  
Plasma Clot ◽  
Colony Stimulating Activity

The regulation of megakaryocytopoiesis is presently poorly understood. Utilizing an in vitro clonal assay system for the human megakaryocytic progenitor cell (CFU-M) we have attempted to define factors which are important in the control of megakaryocytopoiesis at the stem cell level. Sera were obtained from individuals with clinical disorders associated with quantitative platelet abnormalities and were added to plasma clot cultures of bone marrow mononuclear cells obtained from nine normal individuals. When serum samples from nine patients with aplastic anemia comprised 10% of the growth media, each significantly increased CFU-M derived colony formation (400-1250%) when compared to cultures containing normal human AB serum. Under similar conditions, neither sera from eight individuals with thrombocytosis associated with myeloproliferative disorders nor sera from eight patients with severe thrombocytopenia but with normal or increased numbers of bone marrow megakaryocytes (ITP, hypersplenism, TTP, DIC, megakaryocytic leukemia) altered colony formation. When aplastic anemia sera was added in increasing amounts (0, 5, 10, 20, 30%) to bone marrow cultures, CFU-M derived colonies per 5x10$ cells plated increased in a linear fashion (14, 42, 89, 123 and 238, respectively). Preliminary characterization of this megakaryocytic colony stimulating activity (M-CSA) reveals that it is dialyzable and its effect is not neutralized by pretreatment with rabbit anti-erythropoietin antisera. These studies have defined a newly recognized serum factor M-CSA that regulates in vitro megakaryocytic colony formation. M-CSA levels in various disease states suggest that it has physiological significance and that its production might be inversely related to bone marrow megakaryocyte numbers.

scholarly journals Deoxycytidine preferentially protects normal versus leukemic myeloid progenitor cells from cytosine arabinoside-mediated cytotoxicity

Blood ◽  
1987 ◽  
Vol 70 (2) ◽  
pp. 568-571 ◽  
Author(s):  
K Bhalla ◽  
W MacLaughlin ◽  
J Cole ◽  
Z Arlin ◽  
M Baker ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Progenitor Cells ◽  
Colony Formation ◽  
Mononuclear Cells ◽  
Leukemic Cells ◽  
High Dose ◽  
Bone Marrow Mononuclear Cells ◽  
Myeloid Progenitor ◽  
Myeloid Progenitor Cells

Abstract We examined the ability of high concentrations of the naturally occurring nucleoside deoxycytidine (dCyd) to reverse the cytotoxicity of high (eg, greater than or equal to 10(-5) mol/L) concentrations of 1- B-D arabinofuranosylcytosine (Ara-C) toward normal (CFU-GM) and leukemic myeloid progenitor cells (L-CFU). Leukemic myeloblasts from patients with acute nonlymphocytic leukemia (ANLL) and normal human bone marrow mononuclear cells were cultured in soft agar in the continuous presence of 10(-5) to 5 X 10(-5) mol/L of Ara-C together with dCyd (10(-4) to 5 X 10(-3) mol/L). Administration of 10(-5) mol/L of Ara-C alone eradicated colony formation in all samples tested. Coadministration of 10(-3) mol/L of dCyd restored 72.2% of control colony formation for CFU-GM, but only 10.9% for L-CFU. When higher concentrations of Ara-C (eg, 5 X 10(-5) mol/L) were administered, dCyd- mediated protection toward CFU-GM decreased, but remained significantly greater than that observed for L-CFU. Incubation with 10(-3) mol/L of dCyd reduced the 4-hour intracellular accumulation of the triphosphate derivative of Ara-C (Ara-CTP) in both normal and leukemic cells by greater than 98%; under identical conditions, a significant expansion of the intracellular of the triphosphate derivative of dCyd (dCTP) pools was observed in normal bone marrow mononuclear cells but not in leukemic blasts. This finding was associated with a greater reduction in Ara-C DNA incorporation in normal elements. These in vitro studies suggest that dCyd may preferentially protect normal v leukemic myeloid progenitor cells from the lethal actions of high-dose Ara-C.

scholarly journals Deoxycytidine preferentially protects normal versus leukemic myeloid progenitor cells from cytosine arabinoside-mediated cytotoxicity

Blood ◽  
1987 ◽  
Vol 70 (2) ◽  
pp. 568-571
Author(s):  
K Bhalla ◽  
W MacLaughlin ◽  
J Cole ◽  
Z Arlin ◽  
M Baker ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Progenitor Cells ◽  
Colony Formation ◽  
Mononuclear Cells ◽  
Leukemic Cells ◽  
High Dose ◽  
Bone Marrow Mononuclear Cells ◽  
Myeloid Progenitor ◽  
Myeloid Progenitor Cells

We examined the ability of high concentrations of the naturally occurring nucleoside deoxycytidine (dCyd) to reverse the cytotoxicity of high (eg, greater than or equal to 10(-5) mol/L) concentrations of 1- B-D arabinofuranosylcytosine (Ara-C) toward normal (CFU-GM) and leukemic myeloid progenitor cells (L-CFU). Leukemic myeloblasts from patients with acute nonlymphocytic leukemia (ANLL) and normal human bone marrow mononuclear cells were cultured in soft agar in the continuous presence of 10(-5) to 5 X 10(-5) mol/L of Ara-C together with dCyd (10(-4) to 5 X 10(-3) mol/L). Administration of 10(-5) mol/L of Ara-C alone eradicated colony formation in all samples tested. Coadministration of 10(-3) mol/L of dCyd restored 72.2% of control colony formation for CFU-GM, but only 10.9% for L-CFU. When higher concentrations of Ara-C (eg, 5 X 10(-5) mol/L) were administered, dCyd- mediated protection toward CFU-GM decreased, but remained significantly greater than that observed for L-CFU. Incubation with 10(-3) mol/L of dCyd reduced the 4-hour intracellular accumulation of the triphosphate derivative of Ara-C (Ara-CTP) in both normal and leukemic cells by greater than 98%; under identical conditions, a significant expansion of the intracellular of the triphosphate derivative of dCyd (dCTP) pools was observed in normal bone marrow mononuclear cells but not in leukemic blasts. This finding was associated with a greater reduction in Ara-C DNA incorporation in normal elements. These in vitro studies suggest that dCyd may preferentially protect normal v leukemic myeloid progenitor cells from the lethal actions of high-dose Ara-C.

Half-Life of Platelet Factor 4 (PF-4) in Plasma and Platelets from Macaca Mulatta

1977 ◽  
Vol 37 (01) ◽  
pp. 073-080 ◽  
Author(s):  
Knut Gjesdal ◽  
Duncan S. Pepper
Keyword(s):  
Macaca Mulatta ◽  
Half Life ◽  
Human Platelet ◽  
Gel Filtration ◽  
Platelet Factor 4 ◽  
Active Protein ◽  
Platelet Factor ◽  
Membrane Bound

SummaryHuman platelet factor 4 (PF-4) showed a reaction of complete identity with PF-4 from Macaca mulatta when tested against rabbit anti-human-PF-4. Such immunoglobulin was used for quantitative precipitation of in vivo labelled PF-4 in monkey serum. The results suggest that the active protein had an intra-platelet half-life of about 21 hours. In vitro 125I-labelled human PF-4 was injected intravenously into two monkeys and isolated by immuno-precipita-tion from platelet-poor plasma and from platelets disrupted after gel-filtration. Plasma PF-4 was found to have a half-life of 7 to 11 hours. Some of the labelled PF-4 was associated with platelets and this fraction had a rapid initial disappearance rate and a subsequent half-life close to that of plasma PF-4. The results are compatible with the hypothesis that granular PF-4 belongs to a separate compartment, whereas membrane-bound PF-4 and plasma PF-4 may interchange.

scholarly journals Heparin-induced thrombocytopenia: in vitro studies on the interaction of dabigatran, rivaroxaban, and low-sulfated heparin, with platelet factor 4 and anti-PF4/heparin antibodies

Blood ◽  
2012 ◽  
Vol 119 (5) ◽  
pp. 1248-1255 ◽  
Author(s):  
Krystin Krauel ◽  
Christine Hackbarth ◽  
Birgitt Fürll ◽  
Andreas Greinacher
Keyword(s):  
Factor Xa ◽  
Platelet Factor 4 ◽  
Thrombin Inhibitors ◽  
Direct Thrombin Inhibitors ◽  
Platelet Factor ◽  
Heparin Induced Thrombocytopenia ◽  
Alternative Anticoagulation ◽  
Heparin Complexes ◽  
History Of

Abstract Heparin is a widely used anticoagulant. Because of its negative charge, it forms complexes with positively charged platelet factor 4 (PF4). This can induce anti-PF4/heparin IgG Abs. Resulting immune complexes activate platelets, leading to the prothrombotic adverse drug reaction heparin-induced thrombocytopenia (HIT). HIT requires treatment with alternative anticoagulants. Approved for HIT are 2 direct thrombin inhibitors (DTI; lepirudin, argatroban) and danaparoid. They are niche products with limitations. We assessed the effects of the DTI dabigatran, the direct factor Xa-inhibitor rivaroxaban, and of 2-O, 3-O desulfated heparin (ODSH; a partially desulfated heparin with minimal anticoagulant effects) on PF4/heparin complexes and the interaction of anti-PF4/heparin Abs with platelets. Neither dabigatran nor rivaroxaban had any effect on the interaction of PF4 or anti-PF4/heparin Abs with platelets. In contrast, ODSH inhibited PF4 binding to gel-filtered platelets, displaced PF4 from a PF4-transfected cell line, displaced PF4/heparin complexes from platelet surfaces, and inhibited anti-PF4/heparin Ab binding to PF4/heparin complexes and subsequent platelet activation. Dabigatran and rivaroxaban seem to be options for alternative anticoagulation in patients with a history of HIT. ODSH prevents formation of immunogenic PF4/heparin complexes, and, when given together with heparin, may have the potential to reduce the risk for HIT during treatment with heparin.

scholarly journals Interleukin-1β Augments Angiogenic Responses of Murine Endothelial Progenitor Cells in Vitro

2009 ◽  
Vol 29 (5) ◽  
pp. 933-943 ◽  
Author(s):  
Anna Rosell ◽  
Ken Arai ◽  
Josephine Lok ◽  
Tongrong He ◽  
Shuzhen Guo ◽  
...  
Keyword(s):  
Progenitor Cells ◽  
Endothelial Progenitor Cells ◽  
Mononuclear Cells ◽  
Therapeutic Angiogenesis ◽  
Interleukin 1Β ◽  
Endothelial Progenitor ◽  
Angiogenic Potential ◽  
Diphenyl Tetrazolium Bromide ◽  
In Vitro Angiogenesis

Endothelial progenitor cells (EPCs) may provide novel opportunities for therapeutic angiogenesis after ischemic diseases. However, it is unclear how the angiogenic potential of EPCs might be affected by an inflammatory environment. We examine how the potent cytokine interleukin-1β (IL-1β) affects angiovasculogenic responses in EPCs in culture. Mononuclear cells isolated from mouse spleen were plated on fibronectin-coated wells and grown in EGM-2 MV media. Endothelial progenitor cells were phenotyped using multiple markers (UEA-Lectin, ac-LDL, CD133, CD34, vWillebrand Factor, Flk-1) and to identify the IL-1 Receptor-I. We quantified cell and colony counts and performed MTT (3-(4,5-dimethylthiazol-2-yl)2,5-diphenyl-tetrazolium bromide) and Matrigel assays, in vitro, under control and IL-1β (10 ng/mL) conditions. Endothelial progenitor cells exposed to IL-1β increased in the number of cells and colonies compared with untreated cells, without any effect on cell metabolic integrity. Furthermore, IL-1β treatment augmented EPC angiogenic function, significantly increasing the number of vessel-like structures in the Matrigel assay. An early phosphorylation of ERK1/2 occurred after IL-1β stimulation, and this pathway was inhibited if IL-1 Receptor-I was blocked. Our results suggest that IL-1β is a potent stimulator of in vitro angiogenesis through ERK signaling in mouse EPCs. Further studies are warranted to assess how interactions between proinflammatory environments and EPC responses may be leveraged to enhance therapeutic angiogenesis.

Characterisation of the conformational changes in platelet factor 4 induced by polyanions: towards in vitro prediction of antigenicity

2014 ◽  
Vol 112 (07) ◽  
pp. 53-64 ◽  
Author(s):  
Sven Brandt ◽  
Krystin Krauel ◽  
Kay E. Gottschalk ◽  
Thomas Renné ◽  
Christiane A. Helm ◽  
...  
Keyword(s):  
Conformational Changes ◽  
Structural Changes ◽  
Cd Spectroscopy ◽  
Platelet Factor 4 ◽  
Drug Induced ◽  
Platelet Factor ◽  
Preclinical Drug Development ◽  
Varying Length ◽  
Endogenous Proteins

SummaryHeparin-induced thrombocytopenia (HIT) is the most frequent drug-induced immune reaction affecting blood cells. Its antigen is formed when the chemokine platelet factor 4 (PF4) complexes with polyanions. By assessing polyanions of varying length and degree of sulfation using immunoassay and circular dichroism (CD)-spectroscopy, we show that PF4 structural changes resulting in antiparallel β-sheet content >30% make PF4/polyanion complexes antigenic. Further, we found that polyphosphates (polyP-55) induce antigenic changes on PF4, whereas fondaparinux does not. We provide a model suggesting that conformational changes exposing antigens on PF4/polyanion complexes occur in the hairpin involving AA 32–38, which form together with C-terminal AA (66–70) of the adjacent PF4 monomer a continuous patch on the PF4 tetramer surface, explaining why only tetrameric PF4 molecules express “HIT antigens”. The correlation of antibody binding in immunoassays with PF4 structural changes provides the intriguing possibility that CD-spectroscopy could become the first antibody-independent, in vitro method to predict potential immunogenicity of drugs. CD-spectroscopy could identify compounds during preclinical drug development that induce PF4 structural changes correlated with antigenicity. The clinical relevance can then be specifically addressed during clinical trials. Whether these findings can be transferred to other endogenous proteins requires further studies.

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