Murine Granulocyte-macrophage Colony-stimulating Factor Research Articles

Granulocyte-Macrophage Colony-Stimulating Factor mRNA Stabilization Enhances Transgenic Expression in Normal Cells and Tissues

Abstract To increase transgenic production of granulocyte-macrophage colony-stimulating factor (GM-CSF), we mutated the mRNA's 32-untranslated region, AUUUA instability elements. Expression vectors containing human or murine GM-CSF cDNAs coding for wild-type (GM-AUUUA) or mutant versions with reiterated AUGUA repeats (GM-AUGUA) were transfected into cells in culture or animals using particle-mediated gene-transfer technology. Normal peripheral blood mononuclear cells accumulated 20-fold greater levels of GM-CSF mRNA and secreted comparably greater amounts of cytokine after transfection with hGM-AUGUA expression vectors versus hGM-AUUUA. hGM-AUGUA mRNA was fivefold more stable (t 1/2 = 95 minutes) than hGM-AUUUA mRNA (t 1/2 = 20 minutes), accounting for elevated steady-state levels. Transfection site extracts and serum samples obtained 24 hours after gene transfer of hGM-AUGUA cDNA into mouse skin contained greater than 32 ng/mL and 650 pg/mL of GM-CSF protein, respectively, compared with 0.33 ng/mL and less than 8 pg/mL for hGM-AUUUA cDNA. GM-CSF produced from mGM-AUGUA cDNA transfected into rat abdominal epidermis induced a profound neutrophil infiltrate. These data suggest a novel strategy for enhanced production of biologically active cytokines by normal cells after in vivo gene transfer.

Results of a Phase I/II Trial of Recombinant Human Granulocyte-Macrophage Colony-Stimulating Factor in Very Low Birthweight Neonates: Significant Induction of Circulatory Neutrophils, Monocytes, Platelets, and Bone Marrow Neutrophils

Neonates, especially those of very low birthweight (VLBW), have an increased risk of nosocomial infections secondary to deficiencies in development. We previously demonstrated that granulocyte-macrophage colony-stimulating factor (GM-CSF) production and mRNA expression from stimulated neonatal mononuclear cells are significantly less than that from adult cells. Recombinant murine GM-CSF administration to neonatal rats has resulted in neutrophilia, increased neutrophil production, and increased survival of pups during experimental Staphylococcus aureus sepsis. In the present study, we sought to determine the safety and biologic response of recombinant human (rhu) GM-CSF in VLBW neonates. Twenty VLBW neonates (500 to 1,500 g), aged < 72 hours, were randomized to receive either placebo (n = 5) or rhuGM-CSF at 5.0 micrograms/kg once per day (n = 5), 5.0 micrograms/kg twice per day (n = 5), or 10 micrograms/kg once per day (n = 5) given via 2-hour intravenous infusion for 7 days. Complete blood counts, differential, and platelet counts were obtained, and tibial bone marrow aspirate was performed on day 8. Neutrophil C3bi receptor expression was measured at 0 and 24 hours. GM-CSF levels were measured by a sandwich enzyme-linked immunosorbent assay at 2, 4, 6, 12, and 24 hours after the first dose of rhuGM-CSF. At all doses, rhuGM-CSF was well tolerated, and there was no evidence of grade III or IV toxicity. Within 48 hours of administration, there was a significant increase in the circulating absolute neutrophil count (ANC) at 5.0 micrograms/kg twice per day and 10.0 micrograms/kg once per day, which continued for at least 24 hours after discontinuation of rhuGM-CSF. When the ANC was normalized for each patient's first ANC, there was a significant increase in the ANC on days 6 and 7 at each dose level. By day 7, all tested doses of rhuGM-CSF resulted in an increase in the absolute monocyte count (AMC) compared with placebo-treated neonates. In those receiving rhuGM-CSF 5.0 micrograms/kg twice per day, there was additionally a significant increase in the day 7 and 8 platelet count. Tibial bone marrow aspirates demonstrated a significant increase in the bone marrow neutrophil storage pool (BM NSP) at 5.0 micrograms/kg twice per day and 10.0 micrograms/kg once per day. Neutrophil C3bi receptor expression was significantly increased 24 hours after the first dose of rhuGM-CSF at 5.0 micrograms/kg once per day. The elimination half-life (T1/2) of rhuGM-CSF was 1.4 +/- 0.8 to 3.9 +/- 2.8 hours.(ABSTRACT TRUNCATED AT 400 WORDS)

Granulocyte-macrophage colony-stimulating factor mRNA stabilization enhances transgenic expression in normal cells and tissues

To increase transgenic production of granulocyte-macrophage colony-stimulating factor (GM-CSF), we mutated the mRNA's 3'-untranslated region, AUUUA instability elements. Expression vectors containing human or murine GM-CSF cDNAs coding for wild-type (GM-AUUUA) or mutant versions with reiterated AUGUA repeats (GM-AUGUA) were transfected into cells in culture or animals using particle-mediated gene-transfer technology. Normal peripheral blood mononuclear cells accumulated 20-fold greater levels of GM-CSF mRNA and secreted comparably greater amounts of cytokine after transfection with hGM-AUGUA expression vectors versus hGM-AUUUA. hGM-AUGUA mRNA was fivefold more stable (t 1/2 = 95 minutes) than hGM-AUUUA mRNA (t 1/2 = 20 minutes), accounting for elevated steady-state levels. Transfection site extracts and serum samples obtained 24 hours after gene transfer of hGM-AUGUA cDNA into mouse skin contained greater than 32 ng/mL and 650 pg/mL of GM-CSF protein, respectively, compared with 0.33 ng/mL and less than 8 pg/mL for hGM-AUUUA cDNA. GM-CSF produced from mGM-AUGUA cDNA transfected into rat abdominal epidermis induced a profound neutrophil infiltrate. These data suggest a novel strategy for enhanced production of biologically active cytokines by normal cells after in vivo gene transfer.

Granulocyte-macrophage colony stimulating factor and Pneumocystis carinii pneumonia in mice.

We hypothesized that therapy with granulocyte-macrophage colony stimulating factor (GM-CSF) would decrease intensity of murine Pneumocystis carinii pneumonia by upregulating alveolar macrophage function. Mice were depleted of CD4+ T lymphocytes and then inoculated intratracheally with P. carinii. Four weeks later, they received recombinant murine GM-CSF (rmGM-CSF) 5 micrograms/d subcutaneously for 7 and 14 d. At the end of therapy lung tissue was scored for intensity of P. carinii infection by silver methenamine stain and for inflammation by hematoxylin-eosin stain. We found that rmGM-CSF therapy significant decreased the intensity scores of PCP infection in comparison to control mice (1.88 +/- 0.47 vs 3.06 +/- 0.12, p < 0.001). Inflammation scores were not significantly different in the rmGM-CSF group compared with the control group (1.83 +/- 0.47 vs 2.83 +/- 0.67). Alveolar macrophages from mice treated with rmGM-CSF released significantly more tumor necrosis factor-alpha (TNF-alpha) than cells from control mice after in vitro stimulation with lipopolysaccharide (LPS) alone (2.65 +/- 0.30 vs 1.45 +/- 0.26 ng/ml, p = 0.01) or with LPS plus murine recombinant interferon-gamma (4.16 +/- 0.51 vs 2.25 +/- 0.34 ng/ml, p = 0.01). We conclude that GM-CSF therapy reduces the intensity of PCP and this effect is associated with an enhanced alveolar macrophage TNF-alpha production.

Granulocyte-Macrophage Colony Stimulating Factor and Pneumocystis carinii Pneumonia in Mice

We hypothesized that therapy with granulocyte-macrophage colony stimulating factor (GM-CSF) would decrease intensity of murine Pneumocystis carinii pneumonia by upregulating alveolar macrophage function. Mice were depleted of CD4+ T lymphocytes and then inoculated intratracheally with P. carinii. Four weeks later, they received recombinant murine GM-CSF (rmGM-CSF) 5 micrograms/d subcutaneously for 7 and 14 d. At the end of therapy lung tissue was scored for intensity of P. carinii infection by silver methenamine stain and for inflammation by hematoxylin-eosin stain. We found that rmGM-CSF therapy significant decreased the intensity scores of PCP infection in comparison to control mice (1.88 +/- 0.47 vs 3.06 +/- 0.12, p < 0.001). Inflammation scores were not significantly different in the rmGM-CSF group compared with the control group (1.83 +/- 0.47 vs 2.83 +/- 0.67). Alveolar macrophages from mice treated with rmGM-CSF released significantly more tumor necrosis factor-alpha (TNF-alpha) than cells from control mice after in vitro stimulation with lipopolysaccharide (LPS) alone (2.65 +/- 0.30 vs 1.45 +/- 0.26 ng/ml, p = 0.01) or with LPS plus murine recombinant interferon-gamma (4.16 +/- 0.51 vs 2.25 +/- 0.34 ng/ml, p = 0.01). We conclude that GM-CSF therapy reduces the intensity of PCP and this effect is associated with an enhanced alveolar macrophage TNF-alpha production.

Expression of MHC Class II Antigens on Rat Bone Marrow Cells and Macrophages, and Their Modulation during Culture with Murine GM-CSF or M-CSF

Flow cytometric analysis employing MRC OX 6 and MRC OX 17 monoclonal antibodies recognizing determinants on RT1.B or RT1.D molecules, equivalent to murine I-A and I-E, respectively, was used to detect rat MHC class II antigen (Ag) expression. Approximately 5 % of freshly isolated rat bone marrow cells (BMC) expressed RT1.B and over 30 % displayed RT1.D molecules. The RT1.D + cells were W3/13 +, OX 7 +, OX 19 − and OX 22 −. After one week culture of BMC with murine recombinant granulocyte/ macrophage colony-stimulating factor (GM-CSF), regardless of concentrations, 90 to 95 % of the cells were scored as bone marrow-derived macrophages (BMDMΦ), and over 30 % expressed both RT1.B and RT1.D Ag. GM-CSF increases the percentage of BMDMΦ bearing MHC class II Ag in a concentration-dependent manner. This effect seems to be specific because antibodies to interferon-γ, tumor necrosis factor-α or interleukin-4 did not reduce the number of cells expressing RT1.B and RT1.D Ag. Furthermore, GM-CSF was able to trigger expression of class II molecules on rat peritoneal macrophages (MΦ) and BMDMΦ resulted from cultures of BMC with mouse MΦ-CSF (M-CSF), and the RT1.B and RT1.D inducing effect of GM-CSF was opposed by M-CSF, and by anti-GM-CSF antibodies. The induction of MHC class II Ag synthesis by GM-CSF on rat BMDMΦ was confirmed at the mRNA level by Northern blot analysis employing cDNA probes encoding the RT1.B α.

Effects of erythropoietin, IL-3, IL-6 and LIF on a murine megakaryoblastic cell line: Growth enhancement and expression of receptor mRNAs

We examined the effects of recombinant human erythropoietin (rhEPO), recombinant murine interleukin 3 (rmIL-3), recombinant human interleukin 6 (rhIL-6), recombinant human interleukin 11 (rhIL-11), recombinant murine leukemia inhibitory factor (rmLIF) and recombinant murine granulocyte-macrophage colony-stimulating factor (rmGM-CSF) on the growth of murine megakaryocytic cell lines. In serum-free methylcellulose culture supplemented with bovine serum albumin (BSA), the addition of rhEPO (0.12-10 U/ml), rmIL-3 (10-2 500 U/ml), rhIL-6 (100–10000 U/ml), rmLIF (10–1000 U/ml), or rmGM-CSF (10–1000 U/ml) enhanced colony growth in L8057Y5 cells, which had been maintained in protein-free culture, mostly in a dose-dependent fashion; rhIL-11 did not have any stimulatory effect at the tested doses (10–1000 U/ml). In addition, colony growth of L8057 cells, which had been maintained in serum-containing culture, was enhanced, but to a lesser extent, by the addition of these cytokines except rhEPO (the cultures were supplemented with 1% fetal bovine serum. Among the cytokines that showed growth-enhancing effects on L8057 cells, the expression of mRNAs encoding receptors for EPO, IL-6 and IL-3 was examined by northern blot analysis or reverse transcription polymerase chain reaction (RT-PCR). In both cell lines, mRNAs for EPO-R, IL-6R, gp130, IL-3R α and β chains were constitutively expressed. The results suggest that L8057 and L8057Y5 cell lines have characteristics of megakaryoblastic cells in their biological responses to cytokines, as well as in the expression of cytokine receptor mRNAs, and that the growthenhancing effects of these cytokines on the cell lines may be achieved through specific receptors. Our findings show the value of these cell lines for investigating the mechanisms of growth signal transduction in megakaryopoiesis.

Cytokine therapy with gene-transfected cells: single injection of irradiated granulocyte-macrophage colony-stimulating factor-transduced cells accelerates hematopoietic recovery after cytotoxic chemotherapy in mice

Development of cell-based delivery systems that can release therapeutic levels of hematopoietic growth factors into the systemic circulation would facilitate treatment of patients requiring cytokine therapy. In this study, we have investigated the potential of granulocyte- macrophage colony-stimulating factor (GM-CSF)-secreting, irradiated syngeneic murine cells to accelerate hematopoietic recovery after cytotoxic chemotherapy. As a model, CMS-5 fibrosarcoma cells, were transduced with a retroviral vector containing the murine GM-CSF cDNA. Transduced cells secreted 38 ng GM-CSF/10(6) cells in 24 hours. After irradiation, in vitro GM-CSF production initially increased up to fivefold and was measurable for about 2 weeks. One and 2 days after injection of irradiated, GM-CSF-secreting CMS-5 cells (N2/CMVGM- CSF/CMS5 # 6 cells) into mice, GM-CSF serum levels of 405 +/- 58 pg/mL and 183 +/- 36 pg/mL were measured, respectively. Serum levels were comparable with levels detected 3 hours after injection of 100 ng recombinant murine GM-CSF (rmGM-CSF) subcutaneously (90 pg/mL). Injection of N2/CMVGM-CSF/CMS5 # 6 cells in cyclophosphamide-treated mice was as effective in accelerating neutrophil recovery as twice daily subcutaneous injections of rmGM-CSF. These data suggest that irradiated hematopoietic growth factor-secreting cells might offer an alternative to parenteral injections of recombinant cytokines in the treatment of neutropenic patients.

Cytokine Therapy With Gene-Transfected Cells: Single Injection of Irradiated Granulocyte-Macrophage Colony-Stimulating Factor-Transduced Cells Accelerates Hematopoietic Recovery After Cytotoxic Chemotherapy in Mice

Development of cell-based delivery systems that can release therapeutic levels of hematopoietic growth factors into the systemic circulation would facilitate treatment of patients requiring cytokine therapy. In this study, we have investigated the potential of granulocyte-macrophage colony-stimulating factor (GM-CSF)-secreting, irradiated syngeneic murine cells to accelerate hematopoietic recovery after cytotoxic chemotherapy. As a model, CMS-5 fibrosarcoma cells, were transduced with a retroviral vector containing the murine GM-CSF cDNA. Transduced cells secreted 38 ng GM-CSF/10(6) cells in 24 hours. After irradiation, in vitro GM-CSF production initially increased up to fivefold and was measurable for about 2 weeks. One and 2 days after injection of irradiated, GM-CSF-secreting CMS-5 cells (N2/CMVGM-CSF/CMS5 # 6 cells) into mice, GM-CSF serum levels of 405 +/- 58 pg/mL and 183 +/- 36 pg/mL were measured, respectively. Serum levels were comparable with levels detected 3 hours after injection of 100 ng recombinant murine GM-CSF (rmGM-CSF) subcutaneously (90 pg/mL). Injection of N2/CMVGM-CSF/CMS5 # 6 cells in cyclophosphamide-treated mice was as effective in accelerating neutrophil recovery as twice daily subcutaneous injections of rmGM-CSF. These data suggest that irradiated hematopoietic growth factor-secreting cells might offer an alternative to parenteral injections of recombinant cytokines in the treatment of neutropenic patients.

Functional role and signal-induced modulation of proteins recognizing the conserved TCATTT-containing promoter elements in the murine IL-5 and GM-CSF genes in T lymphocytes.

The TCATTT-containing element extending from -61 to -41 of the mouse IL-5 gene is highly conserved in the corresponding region of the granulocyte-macrophage colony-stimulating factor (GM-CSF) gene and has been previously shown to be involved in regulating inducible GM-CSF gene expression. By using stable transfection assays in the mouse Th2 clone D10.G4.1, we show that the TCATTT-containing element is also involved in the regulation of inducible IL-5 gene expression. The mouse IL-5 and GM-CSF homologues of this element were found by gel shift analysis to form DNA-nuclear protein complexes of similar electrophoretic mobility under conditions in which expression of these genes is induced. However, comparative studies using extracts of D10.G4.1 cells treated with the cellular activators Con A and PMA and the inhibitors cycloheximide and cyclosporin A indicated that the binding activities to the conserved elements in the IL-5 and GM-CSF genes (designated NF-IL-5A and NF-GM-CSFA, respectively) are regulated by different signaling pathways. In addition, NF-IL-5A is not induced in the Th1 clone HDK-1 which does not express the IL-5 gene. The strong correlation between the signal-dependent and cell-specific modulation of IL-5 and GM-CSF gene expression patterns and the binding activities of NF-IL-5A and NF-GM-CSFA suggests that these nuclear proteins are involved in the transduction of T cell activation signals to the transcriptional machinery of these genes through their interactions with their respective TCATTT-containing elements.

Immunohistochemical localization of granulocyte-macrophage colony-stimulating factor in matched endometriosis and endometrial tissues

Murine endometrial granulocyte-macrophage colony-stimulating factor has been related to macrophage recruitment and activation and postulated to mediate reproductive events. This study was designed to determine whether granulocyte-macrophage colony-stimulating factor is present in normal human endometrium or endometriosis. Granulocyte-macrophage colony-stimulating factor was immunohistochemically evaluated in matched endometrial and endometriosis biopsy specimens (n = 19) and endometrial biopsy specimens from disease-free patients (n = 8). Staining differences were determined with McNemar's, Fisher's, and Wilcoxon's tests. Granulocyte-macrophage colony-stimulating factor was primarily localized in endometrial and endometriotic epithelial cells. Expression (p = 0.71) and staining intensity (p = 0.37) was similar in matched proliferative-phase endometrium and endometriosis. Matched secretory-phase endometrium and endometriosis also expressed granulocyte-macrophage colony-stimulating factor in similar proportions (p = 0.12), but staining intensity was enhanced in secretory endometriosis compared with secretory endometrium (p = 0.05). Endometrial granulocyte-macrophage colony-stimulating factor did not vary throughout the menstrual cycle, but endometriotic expression (p = 0.013) and staining intensity (p = 0.008) were significantly greater in the secretory phase. Granulocyte-macrophage colony-stimulating factor is localized in endometrial and endometriotic epithelial cells with increased expression in secretory-phase endometriosis. Granulocyte-macrophage colony-stimulating factor may elicit migration, proliferation, and activation of endometrial and peritoneal macrophages.

Granulocyte macrophage colony-stimulating factor improves survival in two models of gut-derived sepsis by improving gut barrier function and modulating bacterial clearance.

The effect of recombinant murine granulocyte macrophage colony-stimulating factor (rmGM-CSF) on survival and host defense was studied using two clinically relevant models of infection that included transfusion-induced immunosuppression. Granulocyte macrophage colony-stimulating factor improves resistance in several models of infection, but its role in transfusion-induced immunosuppression and bacterial translocation (gut-derived sepsis) has not been defined. Balb/c mice were treated with 100 ng of rmGM-CSF or placebo for 6 days in a model of transfusion, burn, and gavage, or cecal ligation and puncture (CLP). Translocation was studied in the first model. Survival after transfusion, burn, and gavage was 90% in rmGM-CSF-treated animals versus 35% in the control group (p < 0.001). After CLP, survival was 75% in the rmGM-CSF group versus 30% in the control group (p = 0.01). Less translocation and better killing of bacteria was observed in the tissues in animals treated with rmGM-CSF. The ability of rmGM-CSF to improve gut barrier function and enhance killing of translocated organisms after burn injury-induced gut origin sepsis was associated with improved outcome. Granulocyte macrophage colony-stimulating factor also improved survival after CLP.

Effect of Granulocyte-Macrophage Colony-Stimulating Factor on Sepsis-Induced Organ Injury in Rats

AbstractThe administration of granulocyte-macrophage colony-stimulating factor (GM-CSF) to patients with severe active infections has been questioned because activation of neutrophils may cause tissue injury. To identify the effect of GM-CSF administration on severe sepsis, we examined the survival rate and pathologic changes in vital organs using the rat lethal sepsis model. Rats received 20 µg of recombinant murine GM-CSF (rmGM-CSF) 3 hours after the onset of peritonitis induced by cecal ligation and puncture. After 48 hours, the survival rate did not improve, and earlier deaths than in the control group were observed. In addition, the inhibition of early leukosequestration in the peritoneal cavity was seen in animals treated with GM-CSF. These results suggested that the administration of rmGM-CSF after the onset of sepsis was not beneficial; thus, we concluded that care should be taken in the clinical use of GM-CSF in severe infection.

Inhibition of Candida albicans growth by murine peritoneal neutrophils and augmentation of the inhibitory activity by bacterial lipopolysaccharide and cytokines.

Anti-Candida activity of murine neutrophils and its regulation by immunomodulators were studied in vitro. Murine neutrophils which were prepared from peritoneal-exudated cells inhibited the growth of Candida albicans at an effector: target (E/T) ratio of 30/1 or above. This anti-Candida activity of neutrophils was augmented by lipopolysaccharide from Escherichia coli, murine tumor necrosis factor (TNF), murine interferon-gamma (IFN-gamma) and murine granulocyte macrophage colony-stimulating factor (GM-CSF) but not by granulocyte colony-stimulating factor (G-CSF) added to the incubation medium. Greater extent of augmentation was obtained when TNF plus GM-CSF or INF-gamma plus GM-CSF were used in combination. These results indicate that anti-Candida activity of murine neutrophils is regulated similarly to that of the human neutrophils reported previously. Therefore murine peritoneal neutrophils can be used as a favorable substitute for human neutrophils in studies on protective machinery against C. albicans infection.

Recombinant GM-CSF reduces lung injury and mortality during neutropenic Candida sepsis.

Cyclophosphamide (CY)-induced neutropenia exacerbates septic shock and acute lung injury during Candida albicans (CA) fungemia in conscious rats. We hypothesized that treatment of such animals with recombinant murine granulocyte-macrophage colony-stimulating factor (GM-CSF) improves host defense during disseminated candidiasis by increasing peripheral neutrophils (PMNs) and enhancing endogenous production of antifungal cytokines including tumor necrosis factor-alpha (TNF). Naive (neutrophil-replete) or neutropenic rats were infected with 10(7) yeast-phase CA; subgroups received GM-CSF (25 micrograms/kg sc) or sterile 0.9% NaCl (NS) twice a day beginning 3 days before CA infection. Arterial hemodynamics, formed blood elements, bioactive TNF in serum and bronchoalveolar lavage fluid (BALF), and lung histopathology were monitored for up to 72 h after infection. All naive animals receiving GM-CSF (n = 5) and 78% of naive rats given NS (n = 9) remained normotensive through 72 h with no lung injury, differing principally in baseline PMNs before CA infection (8.8 +/- 1.8 x 10(3)/microliters, mean +/- SE, vs. 3.7 +/- 0.4 x 10(3)/microliters, respectively, P < 0.01). Neutropenic rats given NS (baseline PMN = 41 +/- 10/microliters, n = 7) were sensitized to CA, and 100% died of hypothermic shock with severe respiratory distress within 56 h of infection. Pulmonary periarterial and alveolar hemorrhage were prominent. Although GM-CSF did not increase baseline PMNs in CY animals by the outset of infection (162 +/- 58/microliters, n = 8), 62% of these rats remained normotensive and eupneic through 72 h (P < 0.01), and their lungs showed no perivascular hemorrhage, alveolar disruption, or fungi.(ABSTRACT TRUNCATED AT 250 WORDS)

Involvement of granulocyte-macrophage colony-stimulating factor in pulmonary homeostasis.

The in vivo function of murine granulocyte-macrophage colony-stimulating factor (GM-CSF) was investigated in mice, carrying a null allele of the GM-CSF gene, that were generated by gene targeting techniques in embryonic stem cells. Although steady-state hematopoiesis was unimpaired in homozygous mutant animals, all animals developed the progressive accumulation of surfactant lipids and proteins in the alveolar space, the defining characteristic of the idiopathic human disorder pulmonary alveolar proteinosis. Extensive lymphoid hyperplasia associated with lung airways and blood vessels was also found, yet no infectious agents could be detected. These results demonstrate that GM-CSF is not an essential growth factor for basal hematopoiesis and reveal an unexpected, critical role for GM-CSF in pulmonary homeostasis.

Proliferation of rat liver macrophages in vitro : Influence of hemopoietic growth factors

We examined the effects of several hemopoietic growth factors on proliferation of rat liver macrophages in vitro. The proliferative response of liver macrophages to hemopoietic growth factors was assayed on the basis of [methyl-3H]thymidine uptake. Macrophage colony-stimulating factor and recombinant murine granulocyte-macrophage colony-stimulating factor stimulated [methyl-3H]thymidine incorporation in a concentration-dependent manner. With granulocyte-macrophage colony-stimulating factor, maximum incorporation was observed at 50 U/ml, whereas with macrophage colony-stimulating factor no incorporation plateau was observed up to 50% L929-conditioned medium. Incubation of liver macrophages with various concentrations of recombinant human interleukin-2, recombinant murine interleukin-3 and recombinant human interleukin-6 or culture medium alone did not result in significant incorporation of [methyl-3H]thymidine. When liver macrophages were fractionated according to cell size, highest incorporation was observed in the large macrophages. Proliferating cells in cultures of all subfractions were microscopically identified as typical macrophages by the use of macrophage-specific monoclonal antibodies. After 6 days in culture, these macrophages had functional properties similar to those of resident liver macrophages with respect to phagocytosis and in vitro activation with immunomodulators to tumorcytotoxicity and secretion of nitric oxide and tumor necrosis factor-alpha. These results suggest that macrophage colony-stimulating factor and granulocyte-macrophage colony-stimulating factor play important roles among the regulatory factors that support local proliferation of rat liver macrophages.

The Macrocyclic Lactone Protein Kinase C Activator, Bryostatin 1, Either Alone, or in Conjunction With Recombinant Murine Granulocyte-Macrophage Colony-Stimulating Factor, Protects Balb/c and C3H/HeN Mice From the Lethal In Vivo Effects of Ionizing Radiation

We have examined the in vivo radioprotective effects of the macrocyclic lactone protein kinase C (PK-C) activator, bryostatin 1, administered either alone or in conjunction with recombinant murine granulocyte-macrophage colony-stimulating factor (rmGM-CSF), in Balb/c and C3H/HeN mice subjected to lethal total body irradiation (TBI). When administered alone on a divided dose schedule (24 hours and 30 minutes before TBI), rmGM-CSF (20 micrograms/kg) was ineffective in increasing survival in either strain. However, in Balb/c mice, bryostatin 1 alone (1 microgram) permitted the long-term survival (60 days) of 70% of the animals following TBI, and 80% when administered in conjunction with rmGM-CSF. Bryostatin 1 administered alone according to this schedule exerted minimal radioprotective effects in C3H/HeN mice, but, when combined with a subeffective dose of rmGM-CSF, allowed 50% of the animals to survive. Treatment of Balb/c mice with bryostatin 1 administered as a single dose 4 hours before TBI resulted in a 20% survival rate, and 45% when administered with rmGM-CSF; corresponding values for the C3H/HeN strain were 60% and 40%, respectively. Lastly, the survival rates of Balb/c mice treated with bryostatin 1 administered as a single dose 4 hours following TBI was 20%, and 25% with rmGM-CSF; corresponding values were 50% and 25% for C3H/HeN mice. These findings indicate that the PK-C activator bryostatin 1 exhibits intrinsic in vivo radioprotective effects in lethally irradiated Balb/c and C3H/HeN mice, and may, under some circumstances, augment the radioprotective capacity of rmGM-CSF. They also underscore the critical role that strain differences and scheduling considerations play in determining the in vivo radioprotective capacity of bryostatin 1, as well as its interactions with rmGM-CSF.

Activation of the Granulocyte-Macrophage Colony-Stimulating Factor Promoter in T Cells Requires Cooperative Binding of Elf-1 and AP-1 Transcription Factors

The granulocyte-macrophage colony-stimulating factor (GM-CSF) gene has been studied extensively as a model system of transcriptional induction during T-lymphocyte activation. The GM-CSF gene is not expressed in resting peripheral blood T cells but is rapidly induced at the transcriptional level following activation through the cell surface T-cell receptor. A highly conserved 19-bp element located immediately 5' of the human GM-CSF TATA box (bp -34 to -52), herein called purine box 1 (PB1), has been shown to bind a T-cell nuclear protein complex and to be required for transcriptional induction of the GM-CSF gene following T-cell activation. The PB1 sequence motif is highly conserved in both human and murine GM-CSF genes. In this report, we demonstrate that the PB1 element alone confers inducibility on a heterologous promoter following transfection into human Jurkat T cells. In addition, we identify a major PB1 nuclear protein-binding complex that is not present in resting peripheral blood T cells but is rapidly induced following T-cell activation. Sequence analysis revealed that PB1 is composed of adjacent binding sites for Ets and AP-1 transcription factors. In vitro mutagenesis experiments demonstrated that both the Ets and AP-1 sites are required for binding of the inducible PB1 nuclear protein complex and for the transcriptional activity of this element and the GM-CSF promoter in activated T cells. Using antibodies specific for different Ets and AP-1 family members, we demonstrate that the major inducible PB1-binding activity present in activated T-cell nuclear extracts is composed of the Elf-1, c-Fos, and JunB transcription factors. Taken together, these results suggest that cooperative interactions between specific Ets and AP-1 family members are important in regulating inducible gene expression following T-cell activation.

Activation of the granulocyte-macrophage colony-stimulating factor promoter in T cells requires cooperative binding of Elf-1 and AP-1 transcription factors.

The granulocyte-macrophage colony-stimulating factor (GM-CSF) gene has been studied extensively as a model system of transcriptional induction during T-lymphocyte activation. The GM-CSF gene is not expressed in resting peripheral blood T cells but is rapidly induced at the transcriptional level following activation through the cell surface T-cell receptor. A highly conserved 19-bp element located immediately 5' of the human GM-CSF TATA box (bp -34 to -52), herein called purine box 1 (PB1), has been shown to bind a T-cell nuclear protein complex and to be required for transcriptional induction of the GM-CSF gene following T-cell activation. The PB1 sequence motif is highly conserved in both human and murine GM-CSF genes. In this report, we demonstrate that the PB1 element alone confers inducibility on a heterologous promoter following transfection into human Jurkat T cells. In addition, we identify a major PB1 nuclear protein-binding complex that is not present in resting peripheral blood T cells but is rapidly induced following T-cell activation. Sequence analysis revealed that PB1 is composed of adjacent binding sites for Ets and AP-1 transcription factors. In vitro mutagenesis experiments demonstrated that both the Ets and AP-1 sites are required for binding of the inducible PB1 nuclear protein complex and for the transcriptional activity of this element and the GM-CSF promoter in activated T cells. Using antibodies specific for different Ets and AP-1 family members, we demonstrate that the major inducible PB1-binding activity present in activated T-cell nuclear extracts is composed of the Elf-1, c-Fos, and JunB transcription factors. Taken together, these results suggest that cooperative interactions between specific Ets and AP-1 family members are important in regulating inducible gene expression following T-cell activation.