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Biomedical subjects

J E Layton

Publications and source records attributed to J E Layton.

At least 19 recordsLinked to original sources
PubMed1996

Tyrosine residues in the granulocyte colony-stimulating factor (G-CSF) receptor mediate G-CSF-induced differentiation of murine myeloid leukemic (M1) cells.

The cytoplasmic tyrosine residues of many growth factor receptors have been shown to be important for receptor signal transduction via the recruitment of proteins containing phosphotyrosine-binding domains. This study demonstrates the importance of specific tyrosine residues in the granulocyte colony-stimulating factor (G-CSF) receptor cytoplasmic domain in G-CSF-induced macrophage cell differentiation. Site-directed mutagenesis was used to generate a series of G-CSF receptor (G-CSF-R) mutants in which the tyrosine residues were replaced with phenylalanine either singly or in combination. The mouse myeloid leukemic cell line (M1) transfected with G-CSF-R cDNA can be induced to differentiate into macrophages in response to G-CSF. The effect of the tyrosine mutations on this differentiation response was assessed by examining cell morphology and differentiation in soft agar colony assays. Although three of the four cytoplasmic tyrosine residues appeared to contribute to the differentiation response, mutation of a single residue (Tyr744) significantly reduced the ability of the M1 cells to differentiate. The STAT family of signaling molecules (Stat1, Stat3, and Stat5) were activated by G-CSF in M1 cells expressing those G-CSF-R tyrosine mutants unable to mediate G-CSF-induced differentiation. Furthermore, activation of STAT proteins was shown to occur in the absence of all four cytoplasmic tyrosine residues, suggesting an alternative mechanism for STAT activation other than direct interaction with receptor phosphotyrosines.

Animals↗
PubMed1996

Expression of granulocyte-colony stimulating factor and its receptor is regulated during the development of the human placenta.

The development of the placenta is dependent upon the regulated proliferation, invasion and differentiation of trophoblast. Expression of cytokines at the feto-maternal interface suggests that these molecules may participate in placentation. The expression of granulocyte-colony stimulating factor (G-CSF) and G-CSF receptor (G-CSFR) during the development of the human placenta was studied by immunohistochemistry using an anti-G-CSF monoclonal antibody (mAb) and two novel anti-G-CSFR mAbs. G-CSF was present in the stroma of fetal chorionic villi and maternal decidual tissues throughout pregnancy. G-CSFR was detected at high levels in fetal first and third, but not second trimester placental tissues. Staining for G-CSFR was undetectable in maternal decidual tissue from all gestational stages. In first trimester tissues, staining for placental G-CSFR was strongest in differentiated syncytiotrophoblast and invasive, extravillous cytotrophoblast, and weak staining was evident in undifferentiated cytotrophoblast. Immunohistochemical data suggesting temporal regulation of G-CSFR were corroborated by Western blotting and amplification by reverse transcription and PCR of G-CSFR mRNA. These data suggested that expression of G-CSFR in the human placenta is regulated both temporally and spatially, and that placental G-CSF is involved in paracrine regulation, and indicate a role for G-CSF and G-CSFR in trophoblast growth or function during placentation.

Base Sequence↗
PubMed1995

Optimizing dose and scheduling of filgrastim (granulocyte colony-stimulating factor) for mobilization and collection of peripheral blood progenitor cells in normal volunteers.

To define an optimal regimen for mobilizing and collecting peripheral blood progenitor cells (PBPC) for use in allogeneic transplantation, we evaluated the kinetics of mobilization by filgrastim (recombinant met-human granulocyte colony-stimulating factor [r-metHuG-CSF]) in normal volunteers. Filgrastim was injected subcutaneously for up to 10 days at a dose of 3 (n = 10), 5 (n = 5), or 10 micrograms/kg/d (n = 15). A subset of volunteers from each dose cohort underwent a 7L leukapheresis on study day 6 (after 5 days of filgrastim). Granulocyte-macrophage colony-forming cell (GM-CFC) numbers in the blood were maximal after 5 days of filgrastim; a broader peak was evident for CD34+ cells between days 4 and 6. The 95% confidence intervals (CI) for mean number of PBPC per milliliter of blood in the three dose cohorts overlapped on each study day. However, on the peak day, CD34+ cells were significantly higher in the 10 micrograms/kg/d cohort than in a pool of the 3 and 5 micrograms/kg/d cohorts. Mobilization was not significantly influenced by volunteer age or sex. Leukapheresis products obtained at the 10 micrograms/kg/d dose level contained a median GM-CFC number of 93 x 10(4)/kg (range, 50 x 10(4)/kg to 172 x 10(4)/kg). Collections from volunteers receiving lower doses of filgrastim contained a median GM-CFC number of 36 x 10(4)/kg (range, 5 x 10(4)/kg to 204 x 10(4)/kg). The measurement of CD34+ cells per milliliter of blood on the day of leukapheresis predicted the total yield of PBPC in the leukapheresis product (r = .87, P < .0001). Assuming a minimum GM-CFC requirement of 50 x 10(4)/kg (based on our experience with autologous PBPC transplantation), all seven leukapheresis products obtained at the 10 micrograms/kg/d dose level were potentially sufficient for allogeneic transplantation purposes. We conclude that in normal donors, filgrastim 10 micrograms/kg/d for 5 days with a single leukapheresis on the following day is a highly effective regimen for PBPC mobilization and collection. Further studies are required to determine whether PBPC collected with this regimen reliably produce rapid and sustained engraftment in allogeneic recipients.

Antigens, CD34↗
PubMed1995

Distinct regions of the granulocyte colony-stimulating factor receptor are required for tyrosine phosphorylation of the signaling molecules JAK2, Stat3, and p42, p44MAPK.

The protein tyrosine kinases JAK1 and JAK2 are phosphorylated tyrosine after the interaction of granulocyte colony-stimulating factor (G-CSF) with its transmembrane receptor. So too is Stat3, a member of the STAT family of transcriptional activators thought to be activated by the JAK kinases. Truncated G-CSF receptor (G-CSF-R) mutants were used to determine the different regions of the cytoplasmic domain necessary for tyrosine phosphorylation of the signaling molecules JAK2, Stat3, and p42, p44MAPK. We have shown that G-CSF-induced tyrosine phosphorylation and kinase activation of JAK2 requires the membrane proximal 57 amino acids of the cytoplasmic domain. In contrast, maximal Stat3 tyrosine phosphorylation required amino acids 96 to 183 of the G-CSF-R cytoplasmic domain, Stat3 DNA binding could occur with a receptor truncated 96 amino acids from the transmembrane domain and containing a single tyrosine residue, but was reduced in comparison with the full-length receptor. Together with the tyrosine phosphorylation of Stat3, this finding suggests that additional Stat3 does not appear to be required for proliferation. MAP kinase tyrosine phosphorylation correlated with both the proliferative response and JAK2 activation.

Amino Acid Sequence↗
PubMed1995

Differential alterations in plasma colony-stimulating factor concentrations in meningococcaemia.

To determine whether circulating levels of any of the colony-stimulating factors (CSF) might contribute to the host response in severe sepsis, plasma concentrations of granulocyte CSF (G-CSF), granulocyte-macrophage CSF (GM-CSF), and macrophage CSF (M-CSF) were measured by immunoassays in 20 subjects with meningococcaemia, a bloodstream infection caused by Neisseria meningitidis, that has proven to be a valuable model to study the responses of other inflammatory mediators during sepsis and septic shock in humans. Plasma G-CSF concentrations were transiently elevated in most subjects during the early phase of meningococcaemia, and were higher in subjects with septic shock (mean +/- s.d. = 165 +/- 142 ng/ml, n = 9) compared with those who remained normotensive (mean +/- s.d. = 7 +/- 2 ng/ml, n = 10) (P < 0.05). Peak plasma G-CSF concentrations > 10 ng/ml were associated with the development of septic shock (P < 0.01), disseminated intravascular coagulation (P < 0.01), fulminant infection (P < 0.05), and a fatal outcome (P < 0.01). Plasma GM-CSF concentrations > 1 ng/ml were briefly present in subjects with life-threatening septic shock (1-15 ng/ml, n = 5), and were strongly associated with fulminant meningococcaemia (P < 0.01). Plasma M-CSF concentrations were marginally elevated in all subjects, but were not associated with complications related to or arising from sepsis-induced organ injury. This study demonstrates that plasma levels of G-CSF, GM-CSF and M-CSF show very different responses during meningococcaemia, changes which presumably reflect the different roles played by these mediators in sepsis and, potentially, in septic shock.

Adolescent↗
PubMed1994

Tyrosine kinase JAK1 is associated with the granulocyte-colony-stimulating factor receptor and both become tyrosine-phosphorylated after receptor activation.

Granulocyte-colony-stimulating factor (G-CSF) stimulates the proliferation and differentiation of cells of the neutrophil lineage by interaction with a specific receptor. Early signal transduction events following G-CSF receptor activation were studied. We detected tyrosine phosphorylation of both the G-CSF receptor and the protein tyrosine kinase JAK1 following G-CSF binding to the human G-CSF receptor. In vitro, the kinase activity of JAK1 was increased by G-CSF stimulation. Coimmunoprecipitation of JAK1 with the G-CSF receptor suggested a physical association which existed prior to G-CSF stimulation.

Animals↗
PubMed1994

Cytomegalovirus infection of vascular endothelial cells alters production of GM-CSF and G-CSF.

Infection of human umbilical vein endothelial cells with the clinical isolate of human cytomegalovirus (HCMV; at a multiplicity of infection of 2) severely suppresses the production of granulocyte-CSF and granulocyte-macrophage-CSF at late stages of infection (6 days post infection onwards). The effect was produced by actively multiplying virus which indicates that HCMV antigen expression is important for this suppression. The suppression in the production of these two cytokines was not due to their accumulation inside the cell nor to cell damage or lysis after infection.

Cells, Cultured↗
PubMed1994

Endogenous haemopoietic growth factors in neutropenia and infection.

Haemopoietic growth factors (HGFs) are being administered to patients with neutropenic fever; however, little is known about the endogenous HGF response in these patients. Specific assays were used to study four HGFs, granulocyte (G-) CSF, granulocyte-macrophage (GM-) CSF, macrophage (M-) CSF and interleukin (IL-) 6 levels in the blood of patients with neutropenic fever (46 episodes). For comparison, levels were also measured in three control populations: normals (20), afebrile neutropenic (14), and bacteraemic but not neutropenic patients (20). In febrile patients, levels of G-CSF (median, range) (0.46, < 0.10-142 ng/ml). IL-6 (0.054, 0.005-24.3 ng/ml) and M-CSF (18.5, 9.9-79.1 ng/ml) were elevated compared with afebrile subjects (< 0.10, < 0.10-1.62 ng/ml). (0.008, 0.002-0.024 ng/ml) and (6.45, < 5.0-31.3 ng/ml) respectively. GM-CSF was not elevated (< 0.02, < 0.02-8.0 ng/ml) compared with afebrile subjects (0.021, < 0.02-0.20 ng/ml). Variables significantly associated (P < 0.05) with elevated cytokine levels were determined by multiple regression analyses. Factors associated with G-CSF elevation were fever, neutropenia, pathogen type and raised bilirubin and creatinine. In contrast, neutropenia was not associated with IL-6 elevation although there was an association between IL-6 elevation and fever, Gram-negative and fungal infections and raised creatinine and bilirubin. M-CSF elevation was associated with fever, renal impairment and known pathogen. Elevated G-CSF and IL-6 levels normalized rapidly (hours-days) with the resolution of infection, whereas M-CSF concentrations remained elevated for up to 10 d. Cytokine levels remained elevated in septic neutropenic patients who did not recover. In summary, G-CSF, IL-6 and M-CSF levels were significantly elevated in sepsis. In contrast, GM-CSF levels were not elevated. These studies should assist the development of therapeutic strategies using HGFs in the treatment of sepsis.

Adolescent↗
PubMed1993

Neutralizing and nonneutralizing monoclonal antibodies to the human granulocyte-macrophage colony-stimulating factor receptor alpha-chain.

A panel of monoclonal antibodies was raised against the low-affinity human granulocyte-macrophage colony-stimulating factor (hGM-CSF) receptor alpha-chain expressed as recombinant protein on murine FDC-P1 cells. All the selected antibodies were of the IgG2A isotype and bound to protein A. They each recognized both native and recombinant receptors by indirect surface immunofluorescence and by immunoprecipitation. Several of the antibodies also recognized presumably denatured receptors as detected by immunoblotting of sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Three different epitopes on the extracellular domain of the GM-CSF receptor alpha-chain were defined by these antibodies, and two of the epitopes did not appear to be involved in binding hGM-CSF or in interactions with the beta-chain of the GM-CSF receptor that are required for high-affinity binding of GM-CSF. On the other hand, the epitope recognized by antibody 2B7-17-A appeared to be critically involved in the binding of GM-CSF because this antibody completely abrogated both high- and low-affinity binding of GM-CSF to native and recombinant receptors. Antibody 2B7-17-A had a relatively high affinity for the GM-CSF receptor alpha-chain (kd = 3 nmol/L) and slow dissociation kinetics (kd = 0.002 min-1). These properties made the 2B7-17-A antibody a potent inhibitor of hGM-CSF biologic action in several different bioassays, with a half-maximal inhibitory dose of about 6 nmol/L (1 microgram/mL). This antibody could prove useful in alleviating any pathologic states mediated by excess GM-CSF levels and in defining the domains of the GM-CSF receptor required for ligand binding.

Animals↗
PubMed1993

Contrasting effects of interleukin-4 on colony-stimulating factor and interleukin-6 synthesis by vascular endothelial cells.

Endothelial cells (EC) may regulate both local and systemic aspects of inflammation through the synthesis of cytokines such as granulocyte-macrophage colony-stimulating factor (GM-CSF), granulocyte colony-stimulating factor (G-CSF), macrophage colony-stimulating factor (M-CSF), and interleukin-6 (IL-6). EC are known to synthesize these cytokines in response to interleukin-1 (IL-1 alpha), tumor necrosis factor-alpha (TNF-alpha) and lipopolysaccharide (LPS). In this paper, we illustrate the effect of interleukin-4 (IL-4) in reducing the synthesis of GM-CSF by EC stimulated with IL-1 alpha, TNF-alpha, or LPS. This is compared with the previously reported strong synergy between IL-4 and IL-1 alpha, TNF-alpha, or LPS in the synthesis of IL-6 by EC. No clear effect of IL-4 was seen in the synthesis of G-CSF or M-CSF. The range of concentrations of IL-4 at which these effects were seen was identical for both reduced GM-CSF synthesis and increased IL-6 synthesis. The effect of IL-4 on IL-6 synthesis was seen by 4 h of treatment, while that on GM-CSF was apparent between 4 and 8 h. It is suggested that these contrasting effects of IL-4 may reflect a biological role for this cytokine in the regulation of leukocytosis and the acute phase response.

Acute-Phase Reaction↗
PubMed1992

Human arterial smooth muscle cells synthesize granulocyte colony-stimulating factor in response to interleukin-1 alpha and tumor necrosis factor-alpha.

Vascular smooth muscle cells (SMC) are a major cell type comprising the walls of blood vessels. We report the synthesis of granulocyte colony-stimulating factor (G-CSF) by cultured human SMC obtained from the internal mammary artery and thoracic aorta. Interleukin-1 alpha (IL-1 alpha) greatly increased in a dose-dependent manner the amount of this cytokine produced by the SMC, with tumor necrosis factor-alpha (TNF-alpha) being less effective. Newly formed G-CSF could be detected in culture supernatants within 6 hours after IL-1 alpha or TNF-alpha treatment. Northern blot analysis of SMC stimulated with IL-1 alpha and TNF-alpha showed an increase in the amount of mRNA for G-CSF as compared with control cells. Enhanced G-CSF mRNA levels were observed when SMC were treated with cycloheximide in the absence or presence of added cytokine. In vasculitis, the walls of blood vessels become inflamed as evidenced by a leucocytic infiltrate usually dominated by polymorphonuclear neutrophil leukocytes (PMNs). G-CSF is known to stimulate PMNs, and our findings raise the possibility that G-CSF made by SMC contributes to the development of vasculitis lesions.

Aorta↗
PubMed1992

Cytokine regulation of colony-stimulating factor (CSF) production in cultured human synovial fibroblasts. II. Similarities and differences in the control of interleukin-1 induction of granulocyte-macrophage CSF and granulocyte-CSF production.

Synovial fibroblasts are likely to be a significant source of granulocyte-macrophage colony-stimulating factor (GM-CSF) and granulocyte-CSF (G-CSF), which could be crucial to the pathogenesis of rheumatoid arthritis. Using specific enzyme-linked immunosorbent assays (ELISAs) and Northern analysis, GM-CSF and G-CSF expression were followed in human synovial fibroblast-like cells in response to a number of agents, either alone or in the presence of an optimal stimulatory concentration of interleukin-1 (IL-1). For both CSFs, interferon-gamma (100 U/mL) did not increase their levels but dramatically suppressed the stimulatory action of IL-1, while basic fibroblast growth factor (10(-8) mol/L), although nonstimulatory by itself, potentiated IL-1 action. The glucocorticoid, dexamethasone (10(-7) mol/L), inhibited IL-1-stimulated CSF production. However, evidence was obtained for noncoordinated CSF regulation. Cyclooxygenase inhibitors potentiated the action of IL-1 on GM-CSF synthesis but suppressed G-CSF synthesis, suggesting that endogenous cyclooxygenase products can have opposite effects in modulating the levels of each CSF. Also, the lymphokine, IL-4 (250 pmol/L), slightly inhibited GM-CSF formation in the presence of IL-1 but elevated the G-CSF levels in these cultures without having an effect by itself. Transforming growth factor beta (less than or equal to 20 ng/mL) did not modulate levels of either CSF. Mesenchymal cell production of both GM-CSF and G-CSF is generally viewed as being under coordinate control; our findings suggest that their synthesis in IL-1-stimulated human synoviocytes can be modulated by a number of agents, in some cases with divergent actions depending on which CSF is examined.

Cells, Cultured↗
PubMed1992

Interleukin-4 suppresses granulocyte colony-stimulating factor and granulocyte-macrophage colony-stimulating factor levels in stimulated human monocytes.

Granulocyte colony-stimulating factor (G-CSF) was quantitated in the supernatants of lipopolysaccharide (LPS)-treated human monocytes by ELISA. Unlike previous reports, the lymphokines, interleukin-4 (IL-4) and interferon-gamma (IFN-gamma), were unable to induce the synthesis of G-CSF. Both IL-4 (> or = 10 pM) and the glucocorticoid, dexamethasone (10(-7) M), inhibited G-CSF production in the LPS-treated monocytes; in contrast, IFN-gamma had a weak potentiating effect on the LPS action. Changes in antigen expression were manifested at the level of messenger RNA (mRNA). Granulocyte-macrophage (GM)-CSF in the LPS-treated monocyte supernatants was also quantitated by ELISA but its levels were somewhat lower than for G-CSF; IL-4, dexamethasone and IFN-gamma had similar effects on GM-CSF levels as on G-CSF levels. The suppression of CSF production in the stimulated monocytes by IL-4 and glucocorticoid extends the list of monocyte cytokines whose levels can be down-regulated by these agents and suggests another potential anti-inflammatory and immunosuppressive function for IL-4.

Cells, Cultured↗
PubMed1991

Identification of a functional domain of human granulocyte colony-stimulating factor using neutralizing monoclonal antibodies.

Human granulocyte colony-stimulating factor (G-CSF) is a hemopoietic growth factor that is being used successfully to treat various forms of neutropenia. To define functionally important regions of G-CSF, we have prepared 37 monoclonal anti-G-CSF antibodies and mapped the regions of G-CSF recognized by different antibody groups. Antibodies recognizing similar epitopes were identified by competition assays, neutralization assays, conformation dependence and cross-reactivity with canine G-CSF. Seven of eight neutralizing antibodies fell into two related epitope groups and were conformation-dependent. The eighth was unrelated and conformation-independent. Peptides of G-CSF were generated by chemical or enzymatic digestion and tested for antibody reactivity. One of the neutralizing antibodies (LMM351) recognized a small, disulfide-bonded peptide from the V8 protease digest (residues 34-46). A synthetic peptide (residues 20-58) was recognized by all the neutralizing antibodies, implicating this disulfide-bonded loop in receptor binding. The epitopes recognized by nonneutralizing antibodies were found throughout G-CSF. Thus, regions of G-CSF that are not involved in receptor binding have also been defined. A CNBr peptide (residues 1-121) had greatly reduced biological activity, indicating that the COOH terminus is required for receptor binding. We predict that residues 20-46 and the COOH terminus bind to the G-CSF receptor.

Amino Acid Sequence↗
PubMed1991

Human articular cartilage and chondrocytes produce hemopoietic colony-stimulating factors in culture in response to IL-1.

The hemopoietic CSF, granulocyte-macrophage CSF (GM-CSF) and granulocyte CSF (G-CSF), are cytokines that mediate the clonal proliferation and differentiation of progenitor cells into mature macrophages and/or granulocytes. We have employed an all-human cell culture system, specific ELISA for GM-CSF and G-CSF, and Northern analysis to investigate whether chondrocytes are a potential source of CSF in rheumatoid disease. We report that human rIL-1 stimulated in a dose-dependent manner the production of GM-CSF and G-CSF by human articular cartilage and chondrocyte monolayers in organ and cell culture, respectively. Increased levels of the CSF Ag were detected after 2 to 8 h stimulation with IL-1, and the optimum dose of IL-1 was 10 to 100 U/ml (0.06 to 0.6 nM IL-1 alpha; 0.02 to 0.2 nM IL-1 beta); neither CSF was detectable in nonstimulated cultures nor in IL-1-stimulated cultures treated with actinomycin D or cycloheximide, indicating the requirement for de novo RNA and protein synthesis. The IL-1-mediated increase in GM-CSF could also be inhibited by the corticosteroid, dexamethasone, but not by the cyclo-oxygenase inhibitor, indomethacin. Although having little effect when tested alone, TNF-alpha and lymphotoxin (TNF-beta) could synergize with IL-1 for the production of GM-CSF. Basic fibroblast growth factor, platelet-derived growth factor, and IFN-alpha and IFN-gamma each had no effect on GM-CSF levels. Results obtained by Northern analysis of chondrocyte total RNA reflected those found for the CSF Ag, namely that CSF mRNA levels were elevated in response to IL-1, but not TNF, and that there was synergy between these two cytokines. We propose that chondrocyte CSF production in response to IL-1, and the concurrent destruction of cartilage by IL-1, could provide a mechanism for the chronic nature of rheumatoid disease.

Cartilage↗
PubMed1991

Chronic neutropenia. A new canine model induced by human granulocyte colony-stimulating factor.

Normal dogs were treated with recombinant human granulocyte colony-stimulating factor (rhG-CSF) at 10 micrograms/kg/day for 30 d, which caused an initial neutrophilia, followed by a prolonged period of chronic neutropenia. A control dog treated with recombinant canine G-CSF (rcG-CSF) showed persistent neutrophilia over 3 mo. Serum from dogs during neutropenia contained an antibody to rhG-CSF, which neutralized the stimulatory effects of both rhG-CSF and rcG-CSF on dog marrow neutrophilic progenitor cell growth and on NFS-60 cell proliferation. 4 mo after discontinuation of rhG-CSF, the dogs' neutrophil counts returned to the normal range. Rechallenge with the rhG-CSF re-induced severe neutropenia in 1 wk. Neutropenia was transferred by plasma infusion from a neutropenic dog to a previously normal dog. These data suggest that human rhG-CSF immunizes normal dogs and thereby induces neutralization of endogenous canine G-CSF and neutropenia. This model system should allow more precise definition of the in vivo role of G-CSF.

Animals↗