scholarly journals Bone Marrow Stroma-Derived Prolactin Is Involved in Basal and Platelet-Activating Factor–Stimulated In Vitro Erythropoiesis

Blood ◽  
1997 ◽  
Vol 90 (1) ◽  
pp. 21-27 ◽  
Author(s):  
Graziella Bellone ◽  
Paola Astarita ◽  
Elisa Artusio ◽  
Stefania Silvestri ◽  
Katia Mareschi ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Cdna Probe ◽  
Platelet Activating Factor ◽  
Pcr Amplification ◽  
Erythroid Differentiation ◽  
Hematopoietic Progenitors ◽  
Gm Csf ◽  
Colony Efficiency

Cooperation between in vitro exogenous prolactin (PRL), granulocyte-macrophage colony-stimulating factor (GM-CSF), and interleukin-3 (IL-3) at an early step of in vitro erythroid differentiation has been shown in a previous study. To gain more insight into the role of PRL in in vivo hematopoiesis, we have now addressed the involvement of endogenous PRL in the growth of hematopoietic progenitors in a bone marrow (BM) stroma environment. The possible modulation of local PRL production by the inflammatory mediator platelet-activating factor (PAF), which is known to be produced by BM cells and to regulate pituitary PRL release, has also been evaluated. Development of burst-forming unit-erythroid (BFU-E) colonies from CD34+ hematopoietic progenitors cultured on a BM stroma cells (BMSC) layer was slightly, but significantly, reduced in the presence of an antihuman PRL antibody. Pretreatment of BMSC with PAF increased the BFU-E colony efficiency of cocultured CD34+ cells, and this effect was completely abrogated by the antiserum. PAF-modulated release of PRL by BMSC was confirmed by an enzyme-linked-immunospot (Elispot) technique. In addition, immunoprecipitation and Western blotting experiments showed two immunoreactive products in the BMSC culture medium. These corresponded to the nonglycosylated (23 kD) and glycosylated (25.5 kD) forms of pituitary PRL that are also expressed by the B-lymphoblastoid cell line IM9-P3. Specific increase of the nonglycosylated form and decrease of the glycosylated form was observed after PAF treatment. Polymerase chain reaction (PCR) amplification of reverse transcribed RNA using PRL-specific primers showed the presence of PRL message in BMSC and IM9-P3 cells. In situ hybridization experiments with a rat PRL cDNA probe cross-reacting with human PRL mRNA confirmed its presence in a small fraction of unstimulated BMSC and in the majority of PAF-stimulated BMSC. The enhancing effect of PAF on PRL-mediated colony formation, PRL release, and mRNA activation was counteracted by pretreating BMSC with the PAF-receptor (R) antagonist WEB 2170. Lastly, responsiveness of BMSC to PAF was substantiated by the presence of the PAF-R mRNA on these cells.

scholarly journals Bone Marrow Stroma-Derived Prolactin Is Involved in Basal and Platelet-Activating Factor–Stimulated In Vitro Erythropoiesis

Blood ◽  
1997 ◽  
Vol 90 (1) ◽  
pp. 21-27 ◽  
Author(s):  
Graziella Bellone ◽  
Paola Astarita ◽  
Elisa Artusio ◽  
Stefania Silvestri ◽  
Katia Mareschi ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Cdna Probe ◽  
Platelet Activating Factor ◽  
Pcr Amplification ◽  
Erythroid Differentiation ◽  
Hematopoietic Progenitors ◽  
Gm Csf ◽  
Colony Efficiency

Abstract Cooperation between in vitro exogenous prolactin (PRL), granulocyte-macrophage colony-stimulating factor (GM-CSF), and interleukin-3 (IL-3) at an early step of in vitro erythroid differentiation has been shown in a previous study. To gain more insight into the role of PRL in in vivo hematopoiesis, we have now addressed the involvement of endogenous PRL in the growth of hematopoietic progenitors in a bone marrow (BM) stroma environment. The possible modulation of local PRL production by the inflammatory mediator platelet-activating factor (PAF), which is known to be produced by BM cells and to regulate pituitary PRL release, has also been evaluated. Development of burst-forming unit-erythroid (BFU-E) colonies from CD34+ hematopoietic progenitors cultured on a BM stroma cells (BMSC) layer was slightly, but significantly, reduced in the presence of an antihuman PRL antibody. Pretreatment of BMSC with PAF increased the BFU-E colony efficiency of cocultured CD34+ cells, and this effect was completely abrogated by the antiserum. PAF-modulated release of PRL by BMSC was confirmed by an enzyme-linked-immunospot (Elispot) technique. In addition, immunoprecipitation and Western blotting experiments showed two immunoreactive products in the BMSC culture medium. These corresponded to the nonglycosylated (23 kD) and glycosylated (25.5 kD) forms of pituitary PRL that are also expressed by the B-lymphoblastoid cell line IM9-P3. Specific increase of the nonglycosylated form and decrease of the glycosylated form was observed after PAF treatment. Polymerase chain reaction (PCR) amplification of reverse transcribed RNA using PRL-specific primers showed the presence of PRL message in BMSC and IM9-P3 cells. In situ hybridization experiments with a rat PRL cDNA probe cross-reacting with human PRL mRNA confirmed its presence in a small fraction of unstimulated BMSC and in the majority of PAF-stimulated BMSC. The enhancing effect of PAF on PRL-mediated colony formation, PRL release, and mRNA activation was counteracted by pretreating BMSC with the PAF-receptor (R) antagonist WEB 2170. Lastly, responsiveness of BMSC to PAF was substantiated by the presence of the PAF-R mRNA on these cells.

Abstract 17293: Hyperglycemia Enhances Pro-Inflammatory Properties of Macrophage-Derived Exosomes to Drive Hematopoiesis in Apolipoprotein E-Deficient Mouse

Circulation ◽  
2020 ◽  
Vol 142 (Suppl_3) ◽  
Author(s):  
Laura Bouchareychas ◽  
Phat Duong ◽  
Tuan Anh Phu ◽  
Eric Alsop ◽  
bessie meechoovet ◽  
...  
Keyword(s):  
Bone Marrow ◽  
High Glucose ◽  
Vascular Inflammation ◽  
Cell Communication ◽  
Chow Diet ◽  
Hematopoietic Progenitors ◽  
Inflammatory Signaling ◽  
Accelerate Atherosclerosis

Introduction: Macrophage-derived exosomes have emerged as important mediators in cell-to-cell communication by influencing inflammatory signaling and the immune function. Hypothesis: We aimed to explore whether hyperglycemia can enhance intercellular communication between mature macrophages and hematopoietic progenitors via exosomes to promote inflammation and diabetic atherosclerosis. Methods: Bone marrow derived macrophages (BMDM) from C57BL/6 mice were cultured with normal (5.5 mM) or high glucose concentrations (25 mM). Exosomes were isolated by cushioned-density gradient ultracentrifugation method followed by nanoparticle tracking and western blot analysis. Inflammatory properties of high glucose exosomes (BMDM-HG-exo) or normoglycemic exosomes (BMDM-NG-exo) were tested in vitro by exposing them to naïve BMDM. The capacity for BMDM-derived exosomes to alter systemic and vascular inflammation were next tested by infusing 25-30 weeks-old ApoE -/- mice fed a chow diet with exosomes three times a week, for four weeks. Results: Our data show that BMDM-HG-exo can stimulate the expression of inflammatory cytokines and generate reactive oxygen species in recipient cultured BMDM. Furthermore, our findings show that intraperitoneally injected exosomes distribute to numerous organs and tissues including the bone marrow and the spleen. HG-exo enhance the expansion of multipotent and lineage committed hematopoietic progenitors in the spleen, leading to an enhanced atherosclerotic progression. Conclusions: We identify that exosomes derived from cultured BMDM exposed to high glucose have the capacity to exert inflammatory signaling in vitro , and in vivo. Our findings suggest that exosomes produced by macrophages exposed to hyperglycemia could represent an unsuspected source of inflammation to accelerate atherosclerosis in diabetes.

scholarly journals Use of 5-fluorouracil to analyze the effect of macrophage inflammatory protein-1 alpha on long-term reconstituting stem cells in vivo

Blood ◽  
1993 ◽  
Vol 81 (6) ◽  
pp. 1497-1504 ◽  
Author(s):  
VF Quesniaux ◽  
GJ Graham ◽  
I Pragnell ◽  
D Donaldson ◽  
SD Wolpe ◽  
...  
Keyword(s):  
Stem Cells ◽  
Bone Marrow ◽  
Inhibitory Effect ◽  
In Vivo Model ◽  
Hematopoietic Progenitors ◽  
Inflammatory Protein ◽  
Macrophage Inflammatory Protein

Abstract A macrophage-derived inhibitor of early hematopoietic progenitors (colony-forming unit-spleen, CFU-A) called stem cell inhibitor was found to be identical to macrophage inflammatory protein-1 alpha (MIP-1 alpha). We investigated the effect of MIP-1 alpha on the earliest stem cells that sustain long-term hematopoiesis in vivo in a competitive bone marrow repopulation assay. Because long-term reconstituting (LTR) stem cells are normally quiescent, an in vivo model was first developed in which they are triggered to cycle. A first 5-fluorouracil (5-FU) injection was used to eliminate later progenitors, causing the LTR stem cells, which are normally resistant to 5-FU, to enter the cell cycle and become sensitive to a second 5-FU injection administered 5 days later. Human MIP-1 alpha administered from day 0 to 7 was unable to prevent the depletion of the LTR stem cells by the second 5-FU treatment, as observed on day 7 in this model, suggesting that the LTR stem cells were not prevented from being triggered into cycle despite the MIP-1 alpha treatment. However, the MIP-1 alpha protocol used here did substantially decrease the number of more mature hematopoietic progenitors (granulocyte-macrophage colony-forming cells [CFC], burst- forming unit-erythroid, CFCmulti, and preCFCmulti) recovered in the bone marrow shortly after a single 5-FU injection. In vitro, MIP-1 alpha had no inhibitory effect on the ability of these progenitors to form colonies. This study confirms the in vivo inhibitory effect of MIP- 1 alpha on subpopulations of hematopoietic progenitors that are activated in myelodepressed animals. However, MIP-1 alpha had no effect on the long-term reconstituting stem cells in vivo under conditions in which it effectively reduced all later progenitors.

scholarly journals In vivo priming of platelet-activating factor-induced eosinophil chemotaxis in allergic asthmatic individuals

Blood ◽  
1992 ◽  
Vol 79 (7) ◽  
pp. 1836-1841 ◽  
Author(s):  
RA Warringa ◽  
HJ Mengelers ◽  
PH Kuijper ◽  
JA Raaijmakers ◽  
PL Bruijnzeel ◽  
...  
Keyword(s):  
Peripheral Blood ◽  
Platelet Activating Factor ◽  
Chemotactic Response ◽  
Healthy Individuals ◽  
Gm Csf ◽  
Asthmatic Patients ◽  
Allergic Asthmatic ◽  
Eosinophil Chemotaxis

Abstract The cytokines granulocyte-macrophage colony-stimulating factor (GM- CSF), interleukin (IL)-3, and IL-5 are important modulators of eosinophilia and eosinophil function. Eosinophil chemotaxis is known to be particularly sensitive for cytokine priming. In the present study, we compared chemotactic responses of eosinophils derived from peripheral blood of allergic asthmatics to responses of eosinophils from peripheral blood of healthy individuals. Eosinophils from allergic asthmatics exhibited a markedly increased sensitivity in their chemotactic response toward platelet-activating factor (PAF) compared with eosinophils from normal donors. In contrast, C5a-induced eosinophil chemotaxis between both groups was similar. This in vivo- primed phenotype could be mimicked in vitro, by preincubating eosinophils from peripheral blood of healthy individuals with picomolar concentrations of either GM-CSF, IL-3, or IL-5. The chemotactic response of eosinophils derived from the circulation of allergic asthmatic patients toward GM-CSF was significantly lower compared with the response of eosinophils of healthy individuals. Our data strongly suggest that release of cytokines may be an important in vivo priming mechanism for eosinophils in the circulation of allergic asthmatic patients. Such an in vivo priming can subsequently result in selective upregulation and downregulation of chemotactic responses toward various chemoattractants release in the lung tissue.

scholarly journals The immunosuppressant rapamycin blocks in vitro responses to hematopoietic cytokines and inhibits recovering but not steady-state hematopoiesis in vivo

Blood ◽  
1994 ◽  
Vol 84 (5) ◽  
pp. 1543-1552 ◽  
Author(s):  
VF Quesniaux ◽  
S Wehrli ◽  
C Steiner ◽  
J Joergensen ◽  
HJ Schuurman ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Steady State ◽  
T Cell ◽  
T Cell Response ◽  
Colony Stimulating Factor ◽  
Gm Csf ◽  
Hematopoietic Recovery ◽  
Stimulating Factor

Abstract The immunosuppressive drug rapamycin suppresses T-cell activation by impairing the T-cell response to lymphokines such as interleukin-2 (IL- 2) and interleukin-4 (IL-4). In addition, rapamycin blocks the proliferative response of cell lines to a variety of hematopoietic growth factors, including interleukin-3 (IL-3), interleukin-6 (IL-6), granulocyte-colony stimulating factor (G-CSF), granulocyte macrophage- colony stimulating factor (GM-CSF), and kit ligand (KL), suggesting that it should be a strong inhibitor of hematopoiesis. In this report, we studied the effects of rapamycin on different hematopoietic cell populations in vitro and in vivo. In vitro, rapamycin inhibited the proliferation of primary bone marrow cells induced by IL-3, GM-CSF, KL, or a complex mixture of factors present in cell-conditioned media. Rapamycin also inhibited the multiplication of colony-forming cells in suspension cultures containing IL-3 plus interleukin-1 (IL-1) or interleukin-11 (IL-11) plus KL. In vivo, treatment for 10 to 28 days with high doses of rapamycin (50 mg/kg/d, orally) had no effect on myelopoiesis in normal mice, as measured by bone marrow cellularity, proliferative capacity, and number of colony-forming progenitors. In contrast, the same treatment strongly suppressed the hematopoietic recovery normally seen 10 days after an injection of 5-fluorouracil (5- FU; 150 mg/kg, intravenously [i.v.]). Thus, rapamycin may be detrimental in myelocompromised individuals. In addition, the results suggest that the rapamycin-sensitive cytokine-driven pathways are essential for hematopoietic recovery after myelodepression, but not for steady-state hematopoiesis.

Leishmania donovani infection of bone marrow stromal macrophages selectively enhances myelopoiesis, by a mechanism involving GM-CSF and TNF-α

Blood ◽  
2000 ◽  
Vol 95 (5) ◽  
pp. 1642-1651 ◽  
Author(s):  
Sara E. J. Cotterell ◽  
Christian R. Engwerda ◽  
Paul M. Kaye
Keyword(s):  
Infectious Disease ◽  
Bone Marrow ◽  
Stromal Cell ◽  
Leishmania Donovani ◽  
Protozoan Parasite ◽  
Gm Csf ◽  
Tnf Α ◽  
Macrophage Colony

Alterations in hematopoiesis are common in experimental infectious disease. However, few studies have addressed the mechanisms underlying changes in hematopoietic function or assessed the direct impact of infectious agents on the cells that regulate these processes. In experimental visceral leishmaniasis, caused by infection with the protozoan parasite Leishmania donovani, parasites persist in the spleen and bone marrow, and their expansion in these sites is associated with increases in local hematopoietic activity. The results of this study show that L donovani targets bone marrow stromal macrophages in vivo and can infect and multiply in stromal cell lines of macrophage, but not other lineages in vitro. Infection of stromal macrophages increases their capacity to support myelopoiesis in vitro, an effect mediated mainly through the induction of granulocyte macrophage-colony stimulating factor and tumor necrosis factor-. These data are the first to directly demonstrate that intracellular parasitism of a stromal cell population may modify its capacity to regulate hematopoiesis during infectious disease.

Treatment with a MEK Inhibitor Improves Myeloproliferation, Anemia and Survival in a Mouse Model of CMML and JMML.

Blood ◽  
2009 ◽  
Vol 114 (22) ◽  
pp. 966-966
Author(s):  
Natalya Lyubynska ◽  
Jennifer Lauchle ◽  
Kevin Shannon ◽  
Benjamin S. Braun
Keyword(s):  
Bone Marrow ◽  
Mouse Model ◽  
Mek Inhibitor ◽  
Colony Growth ◽  
Dramatic Improvement ◽  
Low Concentration ◽  
Gm Csf ◽  
Myeloid Progenitors

Abstract Abstract 966 Mutations that deregulate cellular signaling are a hallmark of myeloproliferative neoplasms (MPNs), and pharmacologic inhibitors of MPN-associated proteins have redefined therapy for some MPNs. However, this strategy cannot yet be applied to juvenile- and chronic myelomonocytic leukemias (JMML and CMML). These diseases are characterized by aberrant N-Ras, K-Ras, Cbl, and SHP-2 proteins that are not easily targeted by drugs. An attractive alternative approach is to inhibit downstream effector pathways, which include the Raf/MEK/ERK, phosphoinositide-3-OH kinase (PI3K)/Akt, and Ral-GDS/Ral-A cascades. However, it is not known which of these pathways are crucial for the aberrant growth and survival of JMML and CMML cells and might therefore provide the best targets for therapy. To address these questions, we developed an accurate mouse model of JMML and CMML by expressing a conditional “knock-in” KrasLSL-G12D oncogene in bone marrow. We administered PD0325901, a potent and selective MEK inhibitor, to Mx1-Cre, KrasG12D mutant mice to test the hypothesis that the Raf→MEK→ERK cascade is necessary for MPN initiated by KrasG12D expression. Oral administration of PD0325901 5 mg/kg caused deep and durable MEK inhibition in primary bone marrow progenitors. Mx1-Cre, KrasG12D mice with established MPN and wild-type (WT) littermates were randomly assigned to receive PD0325901 5 mg/kg/day or a control vehicle. Treated Mx1-Cre, KrasG12D mice demonstrated rapid correction of leukocytosis and anemia, and reduction in splenomegaly. Treatment was also associated with dramatic improvement in the survival of Mx1-Cre, KrasG12D mice (8.1 vs. 2.0 weeks after entry, p=0.003). Two of three Mx1-Cre, KrasG12D mice that were treated for 12 weeks ultimately died with KrasG12D T-lineage leukemia/lymphoma, but none succumbed with progressive MPN. Flow cytometry of bone marrow and peripheral populations showed that PD0325901 reversed the granulocyte/monocyte progenitor bias and ineffective erythropoiesis in KrasG12D mice. However, PD0325901 did not eliminate the rearranged mutant Kras allele in myeloid progenitors, and these cells remained hypersensitive to GM-CSF in methylcellulose cultures. Therefore, PD0325901 did not eliminate Kras mutant cells, but rather modified their behavior in vivo so as to restore a normal output of the hematopoietic system. To further address the biologic effects of PD0325901 on growth of primary progenitor cells in vitro, we examined colony growth over a range of GM-CSF concentrations. Importantly, whereas in vitro exposure to PD0325901 did not selectively abrogate colony growth from bone marrow of naïve Mx1-Cre, KrasG12D mice in the presence of saturating doses of GM-CSF, a low concentration of PD0325901 eliminated the growth of cytokine-independent progenitor colonies. Even more strikingly, this also restored a normal GM-CSF dose response curve in clonogenic progenitors, eliminating the hypersensitive growth pattern that is a hallmark of MPN. Finally, even at saturating doses of GM-CSF, a low concentration of PD0325901 was sufficient to normalize the numbers and types of cells within the colonies. Together, these data show that a low concentration of PD0325901 is sufficient to impart a normal program of proliferation and differentiation in KrasG12D myeloid progenitors. These findings are highly consistent with the in vivo data. Collectively, our data suggest that aberrant MEK activation mediates most aspects of the MPN phenotype in the progenitor compartment and support the development of clinical trials to evaluate MEK inhibitors in patients with JMML and CMML. Disclosures: No relevant conflicts of interest to declare.

Angptl-4 Is Upregulated Under Inflammatory Conditions In The BM Of Mice, Expands Myeloid Progenitors and Accelerates Reconstitution Of Platelets After Myelosuppressive Therapy

Blood ◽  
2013 ◽  
Vol 122 (21) ◽  
pp. 3677-3677
Author(s):  
Anne Schumacher ◽  
Till Braunschweig ◽  
Bernd Denecke ◽  
Tim H. Brümmendorf ◽  
Patrick Ziegler
Keyword(s):  
Bone Marrow ◽  
Conflicts Of Interest ◽  
Myeloid Cell ◽  
Relative Increase ◽  
T Test ◽  
Gm Csf ◽  
Emergency Situations ◽  
Inflammatory Conditions

Abstract The concerted action of hematopoiesis supporting cytokines such as G-CSF, GM-CSF or IL-6 regulates hematopoiesis during steady state and emergency situations. Respective knockout mice show defects both in production and function of myelopoietic effector cells. However, alternative pathways are likely to exist as mice with single or combined deficiencies for G-CSF, GM-CSF, and IL-6 or G-CSF and GM-CSF are still able to mount reactive neutrophilia responses during inflammatory conditions. In order to identify pathways for inflammation induced enhancement of hematopoiesis as well as to find new cytokines, which enhance myeloid cell regeneration, we analyzed the bone marrow (BM) of lipopolysaccharide (LPS) and vehicle injected wild type (WT) mice (single IP- injection) by gene expression microarray. Focusing on the identification of genes encoding for secreted or membrane proteins, we found 83 candidates to be up- and 14 to be downregulated after LPS treatment. Among known candiates, we found angiopoietin-like 4 (Angptl-4) as a predominantly upregulated gene in the BM of LPS-treated WT-mice. Upregulation was confirmed by RT-PCR as well as by Elisa in the BM of LPS treated mice and bone marrow stromal cells (BMSC) were identified as candidate producer cells. Functionally, we found recombinant Angptl-4 to stimulate the proliferation of myeloid colony-forming units (CFU) in vitro. In mice, repeated injections of Angptl-4 increased BM progenitor cell frequency and this was paralleled by a relative increase in phenotypically defined granulocyte-macrophage progenitors (GMPs). Furthermore, in vivo treatment with Angptl-4 resulted in elevated platelet counts both in untreated animals and after myelosuppressive therapy. After lethal irradiation and transplantation of syngeneic BM cells repetitive injections of recombinant Angptl-4 for 5 consecutive days resulted in an accelerated reconstitution of platelets starting at day 8 after transplantation. The 50% pre-treatment platelet count was reached on day 14 in Angptl-4-treated animals as compared to day 21 for transplanted controls receiving no Angptl-4 (n=8; p=0.03, student´s T test). In contrast, transplantation of BM cells from Angptl-4 pre-treated donor mice had no effect on the recovery of platelets in this setting. The frequency of CD41lowCD61+ immature megakaryocytes was significantly increased in the BM of Angptl-4 injected as compared to control mice (27% vs 19% of total megakaryocytes; p= 0.008, student´s T test). Furthermore, bone marrow cytology revealed local accumulation of megakaryocytes carrying dysplastic features in Angptl-4 injected mice. In summary, our data suggest that Angptl-4 plays a complementary role on hematopoiesis during emergency situations like sepsis. The use of Angptl-4 in the setting of autologous stem cell transplantation could represent a potential approach to accelerate the reconstitution of megakaryopoiesis. Disclosures: No relevant conflicts of interest to declare.

Podocalyxin Negatively Regulates Stress Myelopoiesis, Directly Binds Rap-1A and Modulates Its G-CSF-Induced Activity

Blood ◽  
2015 ◽  
Vol 126 (23) ◽  
pp. 1184-1184
Author(s):  
Pan Li ◽  
Rose McGlauflin ◽  
Amanda J Favreau ◽  
Edward Jachimowicz ◽  
Calvin Vary ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Functional Role ◽  
Blood Analysis ◽  
Wild Type ◽  
Hematopoietic Progenitors ◽  
Gm Csf ◽  
Peripheral Blood Analysis ◽  
Specific Deletion

Abstract Podocalyxin (PodxL) is a CD34 family member previously identified to mark hematopoietic stem cells (HSCs) and other progenitor cells. Previously, we discovered PodxL as a potent erythropoietin (EPO) response gene and demonstrated to promote egression of immature reticulocytes from bone marrow into circulation. PodxL is upregulated in several cancers, including myeloid and lymphoid leukemia. Herein, we aim to define the functional role of PodxL in hematopoiesis - specifically myelopoiesis - by employing conditional PodxL knock out (KO) mouse models. Hematopoietic-specific deletion was achieved using Cre mice with a Vav1 driver and myeloid-specific deletion was achieved with Lyzm2 - Cre driver. We confirmed the deletion of exons 3-7 at the gene, transcript and protein levels using PCR, RT-qPCR and western blotting, respectively. Peripheral blood analysis revealed no difference in blood cell lineages for either KO mouse strain. At steady state, colony forming unit-granulocyte/macrophage (CFU-GM) assay also showed no difference between the KO strains and wild type. In order to examine the functional role of PodxL during stress myelopoiesis, PodxL-/- ; Vav1-Cre mice were treated with 5-Fluorouracil (5FU), a chemotherapeutic agent induces myeloablation. Notably, during rebound of neutrophils, the PodxL-/- ; Vav1-Cre mice showed a sharp increase in neutrophil counts at day 12.5, which at later time points reverted to normal levels comparable to wild type mice. Previously, our in silico analyses combined with outcomes from truncated EpoR knock-in alleles had revealed that PodxL is a potential STAT5 transcriptional target. Here, we tested if G-CSF induces PodxL expression in hematopoietic progenitors. In vivo, G-CSF significantly induced PodxL expression four fold. We then tested the role of PodxL in G-CSF induced neutrophil formation in vivo. Both KO strains (Podxl-/-;Vav1-Cre and Podxl-/-;Lyzm2-Cre) and wild type were treated with G-CSF (125ug/kg/day) for 5 days. Peripheral blood analysis revealed increased neutrophil and monocyte levels in the PodxL-/-;Vav1-Cremice. In order to then determine a possible role of PodxL at the progenitor level, CFU-GM assays were performed. PodxL-/- ; lyzm2-Cre mice had increased colony forming capabilities but there was no difference in PodxL-/-;Vav1-Cre mice compared to wild type. Our results imply that PodxL is playing a negative regulatory role in stress myelopoiesis. Interestingly, the deletion of PodxL in hematopoietic progenitors (Vav1-Cre) resulted in enhanced migration of neutrophils, whereas deletion of PodxL in myeloid compartment (Lyzm2-Cre) resulted in decreased neutrophil migration. This may be in part due to a compensatory effect by CD34 in the hematopoietic compartment. To dissect the molecular mechanism of PodxL during stress myelopoiesis, upon in vivo G-CSF treatment, bone marrow derived hematopoietic progenitors were isolated and PodxL protein was immunoprecipitated. LC-MS/MS proteomic analysis was performed to identify the interacting partners with PodxL. Rap-1A, a small GTPase and member of the RAS family, was among the top interacting proteins. Rap-1A has been shown to promote adhesion and migration of myeloid cells. The association of PodxL with Rap-1A was further confirmed in hematopoietic progenitors by immunoprecipitation and western blotting. To determine if the interaction of PodxL directly regulates Rap-1A activity, a GTP-Rap-1A activity assay was performed in response to G-CSF, GM-CSF and IL-3. Rap-1A activity was significantly elevated in hematopoietic progenitors upon G-CSF treatment in PodxL-/-:Vav1-Cre mice compared to wild type, followed by IL3; however, GM-CSF did not affect Rap-1A activity. In conclusion, our results indicate an important functional role for PodxL in stress myelopoiesis, a function likely mediated via Rap-1A. A complete understanding of the PodxL/Rap-1A axis may reveal important molecular insights into G-CSF-induced mobilization of neutrophils and provide mechanistic understanding into the pathological role of PodxL in aggressive cancers, including leukemia, which in turn may facilitate identification of novel therapeutic targets in PodxL associated cancers. Disclosures No relevant conflicts of interest to declare.

scholarly journals In vivo priming of platelet-activating factor-induced eosinophil chemotaxis in allergic asthmatic individuals

Blood ◽  
1992 ◽  
Vol 79 (7) ◽  
pp. 1836-1841 ◽  
Author(s):  
RA Warringa ◽  
HJ Mengelers ◽  
PH Kuijper ◽  
JA Raaijmakers ◽  
PL Bruijnzeel ◽  
...  
Keyword(s):  
Peripheral Blood ◽  
Platelet Activating Factor ◽  
Chemotactic Response ◽  
Healthy Individuals ◽  
Gm Csf ◽  
Asthmatic Patients ◽  
Allergic Asthmatic ◽  
Eosinophil Chemotaxis

The cytokines granulocyte-macrophage colony-stimulating factor (GM- CSF), interleukin (IL)-3, and IL-5 are important modulators of eosinophilia and eosinophil function. Eosinophil chemotaxis is known to be particularly sensitive for cytokine priming. In the present study, we compared chemotactic responses of eosinophils derived from peripheral blood of allergic asthmatics to responses of eosinophils from peripheral blood of healthy individuals. Eosinophils from allergic asthmatics exhibited a markedly increased sensitivity in their chemotactic response toward platelet-activating factor (PAF) compared with eosinophils from normal donors. In contrast, C5a-induced eosinophil chemotaxis between both groups was similar. This in vivo- primed phenotype could be mimicked in vitro, by preincubating eosinophils from peripheral blood of healthy individuals with picomolar concentrations of either GM-CSF, IL-3, or IL-5. The chemotactic response of eosinophils derived from the circulation of allergic asthmatic patients toward GM-CSF was significantly lower compared with the response of eosinophils of healthy individuals. Our data strongly suggest that release of cytokines may be an important in vivo priming mechanism for eosinophils in the circulation of allergic asthmatic patients. Such an in vivo priming can subsequently result in selective upregulation and downregulation of chemotactic responses toward various chemoattractants release in the lung tissue.

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