Absence Of Granulocyte-macrophage Colony-stimulating Factor Research Articles

Inhibition of osteoclastogenesis by interleukin-33 administration in the periodontal ligament under mechanical loading.

The molecular mechanisms mediating external root resorption are poorly understood. Interleukin-33 (IL-33) expression increased remarkably in the periodontal ligament (PDL) under orthodontic loading. The IL-33-driven responses are delicately cell type- and tissue context-dependent. It is unknown how IL-33 act on osteoclastogenesis in the context of root surface. This study aimed to investigate the effect of IL-33 on osteoclastogenesis in the PDL under mechanical loading. C57BL/6J mice were treated with injections of phosphate buffer saline (PBS) or recombinant mouse IL-33 (rmIL-33, 6μl, 30 μg/ml), and subjected to models of orthodontic tooth movement. Tartrated resistant acid phosphates (TRAP)-positive cells and IL-33 expressions were examined in the PDL. IL-33 release from human PDL cells (hPDLCs) was detected by ELISA. Cementoblast-like (OCCM-30) cells were cultured in the presence of rmIL-33 to examine the release of osteoclast-regulatory proteins. The effects of rmIL-33 on osteoclastogenesis were examined in vitro in cultures of bone marrow macrophages (BMMs) and in BMMs-OCCM-30 cocultures. Expressions of osteoclast-specific or -related genes and proteins were investigated in BMMs-OCCM-30 cocultures treated with or without rmIL-33, in the presence or absence of granulocyte-macrophage colony-stimulating factor (GM-CSF) neutralizing antibody. Interleukin-33 expressions were upregulated in the PDL under orthodontic loading. Static compressive force enhanced expression and release of IL-33 from hPDLCs. Administration of rmIL-33 resulted in reduced number of TRAP-positive cells in the PDL, and inhibited osteoclast differentiation from BMMs in vitro. OCCM-30 cells had varied osteoprotegerin (OPG) / receptor activator for nuclear factor-κB ligand (RANKL) secretion and increased release of GM-CSF under rmIL-33 stimulation. Treatment with rmIL-33 in BMMs-OCCM-30 cocultures resulted in inhibited differentiation and decreased activity of osteoclasts, and these effects were partially reversed by GM-CSF neutralizing antibody. Interleukin-33 inhibits osteoclastogenesis in the PDL under orthodontic loading. The anti-osteoclastogenic effects were mediated partly by directly affecting osteoclast precursors and partly by cementoblast-mediated release of GM-CSF.

GM-CSF production by non-classical monocytes controls antagonistic LPS-driven functions in allergic inflammation.

SUMMARYLipopolysaccharide (LPS) can either promote or prevent T helper 2 (Th2) cell allergic responses. However, the underlying mechanism remains unknown. We show here that LPS activity switches from pro-pathogenic to protective depending on the production of granulocyte-macrophage colony-stimulating factor (GM-CSF) by non-classical monocytes. In the absence of GM-CSF, LPS can favor pathogenic Th2 cell responses by supporting the trafficking of lung-migratory dendritic cells (mDC2s) into the lung-draining lymph node. However, when non-classical monocytes produce GM-CSF, LPS and GM-CSF synergize to differentiate monocyte-derived DCs from classical Ly6Chi monocytes that instruct mDC2s for Th2 cell suppression. Importantly, only allergens with cysteine protease activity trigger GM-CSF production by non-classical monocytes. Hence, the therapeutic effect of LPS is restricted to allergens with this enzymatic activity. Treatment with GM-CSF, however, restores the protective effects of LPS. Thus, GM-CSF produced by non-classical monocytes acts as a rheostat that fine-tunes the pathogenic and therapeutic functions of LPS.

Studying the Effects of Granulocyte-Macrophage Colony-Stimulating Factor on Fetal Lung Macrophages During the Perinatal Period Using the Mouse Model.

Background: Granulocyte-macrophage colony-stimulating factor (GM-CSF) is a pro-inflammatory cytokine that is increased in the amniotic fluid in chorioamnionitis and elevated in the fetal lung with endotoxin exposure. Although GM-CSF has a pivotal role in fetal lung development, it stimulates pulmonary macrophages and is associated with the development of bronchopulmonary dysplasia (BPD). How antenatal GM-CSF results in recruitment of lung macrophage leading to BPD needs further elucidation. Hence, we used a transgenic and knock-out mouse model to study the effects of GM-CSF focusing on the fetal lung macrophage.Methods: Using bitransgenic (BTg) mice that conditionally over-expressed pulmonary GM-CSF after doxycycline treatment, and GM-CSF knock-out (KO) mice with no GM-CSF expression, we compared the ontogeny and immunophenotype of lung macrophages in BTg, KO and control mice at various prenatal and postnatal time points using flow cytometry and immunohistology.Results: During fetal life, compared to controls, BTg mice over-expressing pulmonary GM-CSF had increased numbers of lung macrophages that were CD68+ and these were primarily located in the interstitium rather than alveolar spaces. The lung macrophages that accumulated were predominantly CD11b+F4/80+ indicating immature macrophages. Conversely, lung macrophages although markedly reduced, were still present in GM-CSF KO mice.Conclusion: Increased exposure to GM-CSF antenatally, resulted in accumulation of immature macrophages in the fetal lung interstitium. Absence of GM-CSF did not abrogate but delayed the transitioning of interstitial macrophages. Together, these results suggest that other perinatal factors may be involved in modulating the maturation of alveolar macrophages in the developing fetal lung.

In vitro studies to determine the effect of boeravinone B on human dendritic cells

Background: Boeravinone B (BB), a therapeutic biomarker isolated from roots of Boerhavia diffusa, possesses immunomodulatory properties. Objective: In the present study, we investigated cytotoxicity and immunomodulatory effect of BB on human dendritic cells (DCs). Materials and Methods: In this study, buffy coat of human healthy volunteers was collected and the monocytes were separated. Effect of various concentrations of BB on DCs from induced differentiation of monocytes was studied on day 7 using ELISA microplate reader. The effect of BB on the immature DCs generated in the presence and absence of granulocyte-macrophage colony-stimulating factor (GM-CSF) and interleukin4 (IL4) was also noted. The binding of BB with the DC maturation markers CD80, CD83, and CD86 including antigen uptake were evaluated using fluorescent-activated cell sorter (FACS). Results: Viability of DCs was not affected at BB concentration of 100 μg/ml. Phytohemagglutinin (PHA), BB showed increase in DC expression of CD80 expression up to 6.7% (P Abbreviations used: DCs: Dendritic cells, ELISA: Enzyme-linked immunosorbent assay, GMCSF: Granulocyte-macrophage colony-stimulating factor, IL4: Interleukin4, PHA: Phytohemagglutinin, CD: Cluster of differentiation, DMSO: Dimethyl sulfoxide, FACS: Fluorescent activated cell sorter.

GM-CSF in murine psoriasiform dermatitis: Redundant and pathogenic roles uncovered by antibody-induced neutralization and genetic deficiency.

Granulocyte-macrophage colony-stimulating factor (GM-CSF) is a pleiotropic, Th17-derived cytokine thought to critically contribute to the pathogenesis of diverse autoimmune diseases, including rheumatoid arthritis and psoriasis. Treatment with monoclonal antibodies that block GM-CSF activity is associated with favorable therapeutic effects in patients with rheumatoid arthritis. We evaluated the role of GM-CSF as a potential target for therapeutic interference in psoriasis using a combined pharmacologic and genetic approach and the mouse model of imiquimod-induced psoriasiform dermatitis (IMQPD). Neutralization of murine GM-CSF by an anti-GM-CSF antibody ameliorated IMQPD. In contrast, genetic deficiency in GM-CSF did not alter the course of IMQPD, suggesting the existence of mechanisms compensating for chronic, but not acute, absence of GM-CSF. Further investigation uncovered an alternative pathogenic pathway for IMQPD in the absence of GM-CSF characterized by an expanded plasmacytoid dendritic cell population and release of IFNα and IL-22. This pathway was not activated in wild-type mice during short-term anti-GM-CSF treatment. Our investigations support the potential value of GM-CSF as a therapeutic target in psoriatic disease. The discovery of an alternative pathogenic pathway for psoriasiform dermatitis in the permanent absence of GM-CSF, however, suggests the need for monitoring during therapeutic use of long-term GM-CSF blockade.

Granulocyte-macrophage colony stimulatory factor enhances the pro-inflammatory response of interferon-γ-treated macrophages to Pseudomonas aeruginosa infection.

Pseudomonas aeruginosa is an opportunistic pathogen that can cause severe infections at compromised epithelial surfaces, such those found in burns, wounds, and in lungs damaged by mechanical ventilation or recurrent infections, particularly in cystic fibrosis (CF) patients. CF patients have been proposed to have a Th2 and Th17-biased immune response suggesting that the lack of Th1 and/or over exuberant Th17 responses could contribute to the establishment of chronic P. aeruginosa infection and deterioration of lung function. Accordingly, we have observed that interferon (IFN)-γ production by peripheral blood mononuclear cells from CF patients positively correlated with lung function, particularly in patients chronically infected with P. aeruginosa. In contrast, IL-17A levels tended to correlate negatively with lung function with this trend becoming significant in patients chronically infected with P. aeruginosa. These results are in agreement with IFN-γ and IL-17A playing protective and detrimental roles, respectively, in CF. In order to explore the protective effect of IFN-γ in CF, the effect of IFN-γ alone or in combination with granulocyte-macrophage colony-stimulating factor (GM-CSF), on the ability of human macrophages to control P. aeruginosa growth, resist the cytotoxicity induced by this bacterium or promote inflammation was investigated. Treatment of macrophages with IFN-γ, in the presence and absence of GM-CSF, failed to alter bacterial growth or macrophage survival upon P. aeruginosa infection, but changed the inflammatory potential of macrophages. IFN-γ caused up-regulation of monocyte chemoattractant protein-1 (MCP-1) and TNF-α and down-regulation of IL-10 expression by infected macrophages. GM-CSF in combination with IFN-γ promoted IL-6 production and further reduction of IL-10 synthesis. Comparison of TNF-α vs. IL-10 and IL-6 vs. IL-10 ratios revealed the following hierarchy in regard to the pro-inflammatory potential of human macrophages infected with P. aeruginosa: untreated < treated with GM-CSF < treated with IFN-γ < treated with GM-CSF and IFN-γ.

Effect of granulocyte‐macrophage colony‐stimulating factor on neutrophil function in idiopathic bronchiectasis

Neutrophils are consistently found in inflamed and infected airways in idiopathic bronchiectasis, but relatively little is known about the function of blood neutrophils in this condition. We hypothesized that peripheral blood neutrophil (PBN) phagocytosis and superoxide generation are impaired in bronchiectasis, and that granulocyte-macrophage colony-stimulating factor (GM-CSF) is capable of improving neutrophil function. Neutrophils were isolated from the peripheral blood of patients with idiopathic bronchiectasis who were free of exacerbation, and from healthy controls of similar age (n = 21 in both groups). Ingestion of serum-opsonized zymosan by neutrophils was used to quantify phagocytic capacity. Superoxide generation in neutrophils was measured in response to addition of platelet activating factor and formyl-methionyl-leucyl-phenylalanine. Experiments were performed in the presence or absence of GM-CSF. No differences were observed in either phagocytic capacity (P = 0.99) or superoxide generation (P = 0.81) when comparing patients and controls. However, a significant increase in phagocytic capacity above baseline levels in both patients (P < 0.005) and controls (P < 0.005) was induced by GM-CSF. Similarly, the superoxide generation in patients (P < 0.005) and controls (P = 0.001) was significantly increased by GM-CSF. PBN function was preserved in idiopathic bronchiectasis. Enhancement of neutrophil phagocytosis and superoxide generation by GM-CSF requires further study.

Urban Particulate Matter Suppresses Priming of T Helper Type 1 Cells by Granulocyte/Macrophage Colony–Stimulating Factor–Activated Human Dendritic Cells

Urban particulate matter (UPM) exacerbates asthmatic lung inflammation and depresses lung immunity. Lung dendritic cells (DCs) react to airway particulates, and have a critical role in linking innate and adaptive immunity, but the direct effects of UPM on DCs, that have been activated by granulocyte/macrophage colony-stimulating factor (GM-CSF), a product of stimulated normal human bronchial epithelial cells, has not been investigated. Human blood CD1c(+) DCs were purified and activated with UPM in the presence or absence of GM-CSF with and without LPS, and DC maturation was assessed by flow cytometry. DC stimulatory capacity and priming of 5-(and -6)-carboxyfluorescein diacetate succinimidyl ester-labeled naive CD4 T cells was investigated using the allogeneic mixed lymphocyte reaction. T cell proliferation and effector function were assessed using flow cytometry and secreted cytokines were measured by combined bead array. UPM enhanced DC maturation in an LPS-independent manner. DCs activated by UPM plus GM-CSF (UPM + GM-CSF DCs) induced higher naive CD4 T cell proliferation in the allogeneic mixed lymphocyte reaction than DCs pretreated by GM-CSF alone (GM-CSF DCs), and elicited both substantially lower levels of IFN-γ, IL-13, and IL-5 secretion, and lower frequencies of alloantigen-specific T helper (Th) type 1 effector cells than naive CD4 T cells primed by GM-CSF DCs. UPM-stimulated DCs produced IL-6 and TNF-α. Neutralization of IL-6 decreased naive CD4 T cell proliferation stimulated by UPM + GM-CSF DCs, and significantly increased the frequency of alloantigen-specific Th1 effector cells, but did not reverse UPM-induced inhibition of IFN-γ secretion. We conclude that UPM enhances GM-CSF-induced DC maturation and stimulatory capacity, but inhibits the generation of Th1 cells. Thus, UPM exposure may impair Th1 responses to pulmonary pathogens.

CBL Linker Region and RING Finger Mutations Lead to Enhanced Granulocyte-Macrophage Colony-stimulating Factor (GM-CSF) Signaling via Elevated Levels of JAK2 and LYN

Juvenile myelomonocytic leukemia (JMML) is characterized by hypersensitivity to granulocyte-macrophage colony-stimulating factor (GM-CSF). SHP2, NF-1, KRAS, and NRAS are mutated in JMML patients, leading to aberrant regulation of RAS signaling. A subset of JMML patients harbor CBL mutations associated with 11q acquired uniparental disomy. Many of these mutations are in the linker region and the RING finger of CBL, leading to a loss of E3 ligase activity. We investigated the mechanism by which CBL-Y371H, a linker region mutant, and CBL-C384R, a RING finger mutant, lead to enhanced GM-CSF signaling. Expression of CBL mutants in the TF-1 cell line resulted in enhanced survival in the absence of GM-CSF. Cells expressing CBL mutations displayed increased phosphorylation of GM-CSF receptor βc subunit in response to stimulation, although expression of total GM-CSFR βc was lower. This suggested enhanced kinase activity downstream of GM-CSFR. JAK2 and LYN kinase expression is elevated in CBL-Y371H and CBL-C384R mutant cells, resulting in enhanced phosphorylation of CBL and S6 in response to GM-CSF stimulation. Incubation with the JAK2 inhibitor, TG101348, abolished the increased phosphorylation of GM-CSFR βc in cells expressing CBL mutants, whereas treatment with the SRC kinase inhibitor dasatinib resulted in equalization of GM-CSFR βc phosphorylation signal between wild type CBL and CBL mutant samples. Dasatinib treatment inhibited the elevated phosphorylation of CBL-Y371H and CBL-C384R mutants. Our study indicates that CBL linker and RING finger mutants lead to enhanced GM-CSF signaling due to elevated kinase expression, which can be blocked using small molecule inhibitors targeting specific downstream pathways.

Functional evaluation of circulating hematopoietic progenitors in Noonan syndrome

Noonan syndrome (NS) is an autosomal dominant disorder, characterized by short stature, multiple dysmorphisms and congenital heart defects. A myeloproliferative disorder (NS/MPD), resembling juvenile myelomonocytic leukemia (JMML), is occasionally diagnosed in infants with NS. In the present study, we performed a functional evaluation of the circulating hematopoietic progenitors in a series of NS, NS/MPD and JMML patients. The different functional patterns were compared with the aim to identify a possible NS subgroup worthy of stringent hematological follow-up for an increased risk of MPD development. We studied 27 NS and 5 JMML patients fulfilling EWOG-MDS criteria. The more frequent molecular defects observed in NS were mutations in the PTPN11 and SOS genes. The absolute count of monocytes, circulating CD34+ hematopoietic progenitors, their apoptotic rate and the number of circulating CFU-GMs cultured in the presence of decreasing concentrations or in the absence of granulocyte-macrophage colony-stimulating factor (GM-CSF) were evaluated. All JMML patients showed monocytosis >1,000/μl. Ten out of the 27 NS patients showed monocytosis >1,000/μl, which included the 3 NS/MPD patients. In JMML patients, circulating CD34+ cells were significantly increased (median, 109.8/μl; range, 44–232) with a low rate of apoptosis (median, 2.1%; range, 0.4–12.1%), and circulating CFU-GMs were hyper-responsive to GM-CSF. NS/MPD patients showed the same flow cytometric pattern as the JMML patients (median, CD34+ cells/μl, 205.7; range, 58–1374; median apoptotic rate, 1.4%; range, 0.2–2.4%) and their circulating CFU-GMs were hyper-responsive to GM-CSF. These functional alterations appeared 10 months before the typical clinical manifestations in 1 NS/MPD patient. In NS, the CD34+ absolute cell count and circulating CFU-GMs showed a normal pattern (median CD34+ cells/μl, 4.9; range, 1.3–17.5), whereas the CD34+ cell apoptotic rate was significantly decreased in comparison with the controls (median, 8.6%; range, 0–27.7% vs. median, 17.6%; range, 2.8–49.6%), suggesting an increased CD34+ cell survival. The functional evaluation of circulating hematopoietic progenitors showed specific patterns in NS and NS/MPD. These tests are a reliable integrative tool that, together with clinical data and other hematological parameters, could help detect NS patients with a high risk for a myeloproliferative evolution.

Granulocyte-macrophage colony-stimulating factor is a key mediator in experimental osteoarthritis pain and disease development

IntroductionGranulocyte-macrophage colony-stimulating factor (GM-CSF) has been shown to be important in the development of inflammatory models of rheumatoid arthritis and there is encouraging data that its blockade may have clinical relevance in patients with rheumatoid arthritis. The aims of the current study were to determine whether GM-CSF may also be important for disease and pain development in a model of osteoarthritis.MethodsThe role of GM-CSF was investigated using the collagenase-induced instability model of osteoarthritis. We studied both GM-CSF-/- mice and wild-type (C57BL/6) mice treated prophylactically or therapeutically with a monoclonal antibody to GM-CSF. Disease development (both early and late) was evaluated by histology and knee pain development was measured by assessment of weight distribution.ResultsIn the absence of GM-CSF, there was less synovitis and matrix metalloproteinase-mediated neoepitope expression at week 2 post disease induction, and less cartilage damage at week 6. GM-CSF was absolutely required for pain development. Therapeutic neutralization of GM-CSF not only abolished the pain within 3 days but also led to significantly reduced cartilage damage.ConclusionsGM-CSF is key to the development of experimental osteoarthritis and its associated pain. Importantly, GM-CSF neutralization by a therapeutic monoclonal antibody-based protocol rapidly and completely abolished existing arthritic pain and suppressed the degree of arthritis development. Our results suggest that it would be worth exploring the importance of GM-CSF for pain and disease in other osteoarthritis models and perhaps clinically for this form of arthritis.

Regulation of systemic and local myeloid cell subpopulations by bone marrow cell–derived granulocyte–macrophage colony‐stimulating factor in experimental inflammatory arthritis

Even though there are clinical trials assessing granulocyte-macrophage colony-stimulating factor (GM-CSF) blockade in rheumatoid arthritis (RA), questions remain as to how GM-CSF acts as a proinflammatory cytokine. The aims of this study on the regulation of arthritis progression by GM-CSF were to determine the source of the GM-CSF, whether there are systemic effects, the changes in synovial tissue leukocyte populations, and the arthritis model dependence on GM-CSF. Bone marrow chimeras were used to determine the source of GM-CSF required for the development of collagen-induced arthritis (CIA). The K/BxN serum-transfer model of arthritis was tested in GM-CSF(-/-) mice and using anti-GM-CSF monoclonal antibodies. Cell populations from arthritic mice were assessed by differential staining and flow cytometry. In the CIA model, GM-CSF produced by bone marrow-derived cells was required for arthritis development. GM-CSF blockade, while ameliorating the development of CIA, was found to have systemic effects, limiting the increase in circulating Ly-6C(high) monocytes and neutrophils. GM-CSF blockade led to fewer synovial macrophages (both Ly-6C(high) and Ly-6C(low)), neutrophils, and lymphocytes. In the absence of GM-CSF, K/BxN serum-transfer arthritis initially developed normally; however, the numbers of Ly-6C(high) monocytes and synovial macrophages (both Ly-6C(high) and Ly-6C(low)) were again reduced, along with the peak disease severity and maintenance. GM-CSF is a key player in two arthritis models, participating in interactions between hemopoietic cells, both locally and systemically, to control myeloid cell numbers as well as presumably to "activate" them. These results could be useful for the analysis of current clinical trials targeting GM-CSF in patients with RA.

Identification of a novel immunosuppressive dendritic cell population derived from conventional DC (113.5)

Abstract Dendritic cells (DC) play a central role in the initiation and regulation of immune responses. Conventional DC (cDC) arise from circulating immediate precursors (pre-cDC) and are currently thought to be terminally differentiated. Here we show, however, that cDC are capable of generating progeny that lost all characteristic features of cDC; and investigate the functional properties of this novel population. Sorted bone marrow pre-cDCs were cultured on a stromal monolayer in the presence/absence of granulocyte-macrophage colony stimulating factor (GM-CSF). On day three, proliferating CD11c+ MHCII+ cDC developed in both cultures. However, in the absence of GM-CSF, these cells gave rise to a homogeneous population of CD11clow MHClow cells (DC-regs) on day 8-10 of culture. In contrast to cDCs, DC-regs failed to up-regulate MHCII and co-stimulatory molecules in response to DC maturation stimuli. DC-regs displayed higher antigen capture capacity but were poor stimulators in T cell proliferation assays. Further, DC-regs not only induced T cell anergy, but also suppressed T cell proliferation in cultures containing immuno-stimulatory DC. Co-transfer of DC-regs with DCs in vivo inhibited T cell proliferation. DC-regs expressed know immunosuppressive molecules such as iNOS, arginase, ICOSL and PD-L1. Our findings challenge the prevalent view that cDC are terminally differentiated, and reveal their potential to generate a regulatory DC population with potent immunosuppressive properties.

The Role of Granulocyte Macrophage‐Colony Stimulating Factor in Gastrointestinal Immunity to Salmonellosis

Human Salmonella infection, in particular, typhoid fever is a highly infectious disease that remains a major public health problem causing significant morbidity and mortality. The outcome of these infections depends on the host's immune response, particularly the actions of granulocytes and macrophages. Using a mouse model of human typhoid fever, with Salmonella typhimurium infection of wild type and granulocyte macrophage-colony stimulating factor (GM-CSF) knock out mice we show a delay in the onset of immune-mediated tissue damage in the spleens and livers of GM-CSF(-/-) mice. Furthermore, GM-CSF(-/-) mice have a prolonged sequestration of S. typhimurium in affected tissues despite an increased production of F4/80+ effector cells. Moreover in the absence of GM-CSF, a decrease in pro-inflammatory cytokine expression of tumor necrosis factor-alpha, interleukin-12 (IL-12) and IL-18 was found, which may alter the host's immune response to infection. GM-CSF appears to play an important role in the pathogenesis of Salmonellosis, and may contribute significantly to the development of protective gastrointestinal mucosal immune responses against oral pathogens.

125. REGULATION OF STRESS PROTEIN GENES DURING PRE-IMPLANTATION EMBRYO DEVELOPMENT IN MICE BY GRANULOCYTE-MACROPHAGE COLONY-STIMULATING FACTOR (GM-CSF)

In vitro culture has been shown to be detrimental for pre-implantation embryo development and this has been associated with culture stress and elevated expression of apoptotic genes. Granulocyte-macrophage colony-stimulating factor (GM-CSF) has been shown to promote development and survival of both human and mouse pre-implantation embryos. To investigate the mechanism of action of GM-CSF in mouse embryos, gene expression was examined in in vitro cultured blastocysts with and without recombinant mouse GM-CSF (rmGM-CSF) and in vivo blastocysts flushed from Csf2 null mutant and wild-type mice. Microarray analysis of the effect of GM-CSF on transcription profile implicated apoptosis and stress response gene pathways in blastocyst responses to rmGM-CSF in vitro. Groups of 30 blastocysts were collected from in vitro cultured and in vivo developed blastocyst were analysed using quantitative real-time polymerase chain reaction (qRT-PCR). qRT-PCR analysis of in vitro blastocysts revealed that addition of rmGM-CSF causes differential expression of several genes associated with apoptosis and cellular stress pathway, including Cbl, Hspa5, Hsp90aa1, Hsp90ab1 and Gas5. Immunocytochemical analysis of common proteins of the apoptosis and cellular stress response pathways BAX, BCL2, TRP53 (p53) and HSPA1A/1B (Hsp70) in in vitro blastocysts revealed that HSPA1A/1B and BCL2 proteins were less abundant in embryos cultured in rmGM-CSF, but BAX and TRP53 were unchanged. In in vivo developed blastocysts, Csf2 null mutation resulted in elevated levels of only the heat shock protein Hsph1, suggesting that in vivo, other cytokines can compensate for GM-CSF deficiency as the absence of GM-CSF has a lesser effect on the stress response pathway. We conclude that GM-CSF is a regulator of the apoptosis and cellular stress response pathways influencing mouse pre-implantation embryo development to facilitate embryo growth and survival, and the effects of GM-CSF are particularly evident in in vitro culture media in the absence of other cytokines.

The effects of recombinant granulocyte-macrophage colony-stimulating factor (GM-CSF) and interleukin-3 on the secretory capacity of human blood eosinophils

The effects of recombinant human GM-CSF and interleukin-3 (IL-3) on human blood eosinophil survival, activation, and secretion were studied. Purified normal density eosinophils from patients with the idiopathic hypereosinophilic syndrome (HES) survived in culture for 7 days (50% viable) in the presence of 50 nM GM-CSF or 50 nM IL-3. Neutrophils did not survive after 4 days. No eosinophils survived in the absence of GM-CSF or IL-3. In two out of five patients studied, the cultured eosinophils became elongated with numerous processes. In all five patients the cells became adherent, but there were no morphological signs of degranulation. Both GM-CSF and IL-3 activated eosinophils, transforming the storage form of eosinophil cationic protein (ECP) into the secreted form. The proportion of activated cells increased from less than 20% to over 50% after 4 days in culture. However, GM-CSF and IL-3 did not induce secretion on their own. On the other hand, when GM-CSF/IL-3-activated eosinophils were exposed to known secretory stimuli, there was a six-fold increase in the amount of ECP released when the cells were stimulated with sepharose coated with C3b, and a two-fold increase when they were stimulated with sepharose-activated whole autologous serum. Eosinophils from patients taking steroids were unable to secrete their granule contents, even though they became activated by GM-CSF and IL-3. A novel finding was that sepharose-activated whole serum was an extremely potent secretory signal for ECP, releasing up to 50% of the total ECP content. These studies showed that GM-CSF and IL-3 prime eosinophil effector function by initiating granule solubilization which is the first step in the secretory event, without affecting the subsequent extracellular release of granule proteins.

Role of Downstream Effectors in Kras-Driven Myeloproliferative Disease.

Mutations that deregulate Ras signaling are highly prevalent in myeloid malignancies. Previous work has shown that expressing oncogenic KrasG12Din hematopoietic cells from the endogenous Kras promoter leads to growth factor-independent and hypersensitive myeloid progenitor colony formation, and causes a fatal myeloproliferative disorder (MPD) (Braun et al PNAS 101:597, 2004; Chan et al JCI 113:528, 2004). These characteristics mirror the human juvenile and chronic myelomonocytic leukemias (JMML and CMML) - diseases that are associated with Ras pathway mutations. Oncogenic Ras accumulates in its active GTP-bound form and constitutively activates a number of downstream effectors. However, it is unclear which effectors are necessary for the maintenance of disease as well as how they contribute to specific phenotypes such as enhanced proliferation and defective apoptosis. We constructed second site mutants - secondary mutations on a backbone of KrasG12D(G12D) that prevent K-RasG12D from binding to a subset of effectors - to begin to elucidate the individual contributions of downstream effector pathways to hematologic disease. Murine fetal liver cells engineered to express KrasG12D,E37G(E37G) and KrasG12D,Y64G(Y64G) second site mutants maintain a hypersensitive pattern of colony-forming unit granulocyte-macrophage (CFU-GM) colony growth in response to granulocyte-macrophage colony-stimulating factor (GM-CSF), but are no longer able to grow in the absence of GM-CSF. Interestingly, both mutant proteins that display hypersensitivity also hyperactivate two major Ras effector pathways, as opposed to other second site mutants tested which only hyperactivate one major Ras effector pathway and do not show growth factor hypersensitivity. Whereas E37G activates both PI3 kinase and Ral-GDS but not Raf, Y64G stimulates Raf/MEK/ERK and PI3 kinase but not Ral-GDS. Consistent with the idea that activation of at least two effector cascades is required for aberrant in vitro growth, expression of activated effectors BrafV600E, p110a-CAAX, and RalGDS-CAAX did not confer GM-CSF hypersensitivity on CFU-GM colonies. We transplanted bone marrow cells transduced with MSCV-E37G-IRES-GFP or MSCV-Y64G-IRES-GFP retroviruses into lethally irradiated Balb/c mice. Seven of 8 mice that received Y64G cells died of T lineage acute lymphoid leukemia/lymphoma (T-ALL/L) with a median survival of 112 days. Diseased animals showed very high levels of GFP in the thymus, spleen, peripheral blood and bone marrow. Four of 9 mice injected with E37G-expressing cells mice also died of T-ALL/L with a median survival of 106 days and three of 9 died of anemia. None of the MIG mice (n=8) have died of leukemia/lymphoma. The Y64G and E37G T ALL/Ls studied to date are transplantable into sublethally irradiated recipients. We conclude that second site mutations in the KrasG12Doncogene that are defective for activation of either PI3 kinase or Raf/MEK/ERK are able to deregulate the growth of primary hematopoietic cells in vitro and in vivo. These data argue that targeting a single effector pathway downstream of oncogenic Ras may not be effective in many hematologic malignancies. We are interrogating Ras signaling networks in T-ALL/L cells and cloning MSCV integration sites to further characterize the effects of these second site mutant alleles.

CBAP interacts with the un-liganded common β-subunit of the GM-CSF/IL-3/IL-5 receptor and induces apoptosis via mitochondrial dysfunction

The cytoplasmic domain of the common beta-chain (betac) of the granulocyte-macrophage-colony-stimulating factor (GM-CSF)/interleukin-3 (IL-3)/IL-5 receptor contains a membrane proximal region that is sufficient to mediate ligand-dependent mitogenic activity. Within this region two motifs, designated as box 1 and box 2, are highly conserved among members of the cytokine receptor superfamily. Whereas box 1 is required for the recruitment and phosphorylation of Janus kinase-2, the function of box 2 remains largely unknown. Here, we report the identification of a novel transmembrane protein (common beta-chain associated protein (CBAP)) which directly associated with betac via the box 2 motif. Interestingly, such an association only occurred in the absence of GM-CSF in vivo. Ectopic overexpression of CBAP triggered apoptosis of factor-dependent cells via mitochondrial dysfunction, which could be inhibited by Bcl-2 overexpression. Reduced expression of endogenous CBAP by small interfering RNA did not interfere GM-CSF-activated signaling molecules, but such treatment significantly inhibited apoptosis induced by GM-CSF deprivation, but not other death stimuli. Domain mapping studies indicated that one apoptogenic domain of CBAP correlated with its ability to interact with betac. Taken together, these results suggest that CBAP modulates GM-CSF-deprivation-induced apoptosis possibly via a novel mechanism involving interaction with an un-liganded betac molecule.

Role of Granulocyte Macrophage Colony-Stimulating Factor in Host Defense Against Pulmonary Cryptococcus neoformans Infection during Murine Allergic Bronchopulmonary Mycosis

We investigated the role of granulocyte macrophage colony-stimulating factor (GM-CSF) in host defense in a murine model of pulmonary cryptococcosis induced by intratracheal inoculation of Cryptococcus neoformans. Pulmonary C. neoformans infection of C57BL/6 mice is an established model of an allergic bronchopulmonary mycosis. Our objective was to determine whether GM-CSF regulates the pulmonary Th2 immune response in C. neoformans-infected C57BL/6 mice. Long-term pulmonary fungistasis was lost in GM-CSF knockout (GM(-/-)) mice, resulting in increased pulmonary burden of fungi between weeks 3 and 5. GM-CSF was required for the early influx of macrophages and CD4 and CD8 T cells into the lungs but was not required later in the infection. Lack of GM-CSF also resulted in reduced eosinophil recruitment and delayed recruitment of mononuclear cells into the airspace. Macrophages from GM(+/+) mice showed numerous hallmarks of alternatively activated macrophages: higher numbers of intracellular cryptococci, YM1 crystals, and induction of CCL17. These hallmarks are absent in macrophages from GM(-/-) mice. Mucus-producing goblet cells were abundantly present within the bronchial epithelial layer in GM(+/+) mice but not in GM(-/-) mice at week 5 after infection. Production of both Th1 and Th2 cytokines was impaired in the absence of GM-CSF, consistent with both reduced C. neoformans clearance and absence of allergic lung pathology.

Effect of granulocyte–macrophage colony stimulating factor on growth, resistance to freezing and thawing and re-expansion of murine blastocysts

Two-cell murine embryos were cultured for 72 h in the presence or absence of granulocyte-macrophage colony stimulating factor (GM-CSF), frozen for 60 days and, after thawing, cultured for an additional 24 h in the presence or absence of GM-CSF. During the initial 72 h period, GM-CSF did not influence the percentage of embryos reaching the expanded blastocyst stage, but there was a significant increase ( P < 0.05) in the number of cells in the embryos grown with GM-CSF. Survival after thawing was not affected by previous exposure to GM-CSF, but re-expansion of the blastocoele was diminished in that group. Exposure to GM-CSF during the post-thaw period greatly enhanced re-expansion of the blastocoele. The presence of human serum albumin in the culture media is thought to have masked the beneficial effect of GM-CSF upon embryos.