GM-CSF derived from alveolar type 2 cells promotes CD301b+ cDC2 generation and allergic airway inflammation.

this issue of the American Journal of Physiology-Lung Cellular and Molecular Physiology features nine articles that provide new insights into the mechanisms and the cellular pathways that regulate ion transport across the distal pulmonary epithelia in both the adult and fetal lung. Although much has

Background Giant Cell Arteritis (GCA) is a type of large vessel vasculitis that can cause blindness and aortic aneurysms. A significant unmet medical need remains in GCA, as current treatment options are limited, and relapse increases corticosteroid (CS) exposure and toxicity. The primary role of macrophages/dendritic cells (DCs) and TH1/TH17 lymphocytes in GCA pathogenesis has been highlighted previously. Granulocyte-macrophage colony stimulating factor (GM-CSF) may contribute to GCA pathogenesis by stimulating giant cell formation.1 GM-CSF produced by CD4+ T helper TH1 and TH17 cells can stimulate conventional DCs and promote differentiation of monocyte-derived DCs.2 GM-CSF may drive DCs to program naive CD4+ cells to TH1, TH17, and T follicular helper phenotypes (IFNγ/IL-17/IL-21). Notably GM-CSF RNA has been reported in GCA lesions3 and in peripheral blood mononuclear cells of symptomatic patients.4 Objectives We hypothesized elevation of the GM-CSF pathway signature in GCA vessels versus controls. Methods Two independent sources of temporal artery biopsies were utilized. First, GCA (n=17) and control (symptomatic patients suspected for GCA, but with a normal temporary artery biopsy; n=5) biopsies were analyzed for 15 mRNA transcripts representing TH1, TH17, and GM-CSF signaling (RNAscope; RS) and for mRNA transcripts representing the autoimmune panel (Nanostring; NS). Semi-quantitative scoring was performed on RS images, and fold-change of representative TH1, TH17 and GM-CSF related mRNA transcripts were calculated via NS nCounter analysis. Additional GCA and control biopsies were obtained and analyzed by RT-PCR for a subset of transcripts (n=10 each) and by confocal microscopy for GM-CSF and GM-CSF-Rα protein (n=2 each). Results The GM-CSF signaling pathway molecular signature was confirmed to be upregulated by 4 independent analyses. GM-CSF-associated and TH1-associated genes were upregulated in GCA biopsies versus control (GMCSF: 3-4x RS; GM-CSF-Rα: 6.7x NS, 6x RS; and CD83: 3.9x NS, 6x RS; TNFα: 2x NS, 3x RS; IFNγ: 2x RS; IL-1β: 6x RS). TH17 associated genes were not elevated, potentially due to concomitant CS treatment. Upregulation of both GM-CSF (12x) and GM-CSF-Rα (3x) mRNA was confirmed in a separate cohort of biopsies from GCA patients vs. controls by RT-PCR (Figure). GM-CSF and GM-CSFRα proteins were detected in the luminal endothelium, neovessels and inflammatory cells of GCA patients. In normal temporal arteries, GM-CSF protein was not detected, and some GM-CSFRα expression was observed in the luminal endothelium. Pu.1, a transcription factor downstream of GM-CSF signaling, was increased 8x in GCA vs. controls (RS, NS) (Figure). Conclusion GM-CSF and TH1 pathway signatures were demonstrated in GCA patient temporal arteries by independent analytical techniques. Active GM-CSF signaling in diseased tissue is evidenced by increased expression of Pu.1 in the vessel wall. These data implicate the GM-CSF pathway in GCA pathophysiology and increase confidence in rationale for targeting GM-CSF in GCA.

Chronic alcohol abuse predisposes individuals to pneumonia and increases the risk ˜4-fold of developing the acute respiratory distress syndrome. Although it has been recognized for decades that alcohol abuse impairs...

Alcohol abuse dramatically increases the risk of acute lung injury. In an experimental rat model of ethanol-mediated susceptibility to lung injury, recombinant granulocyte/macrophage colony-stimulating factor (GM-CSF) restored alveolar epithelial barrier function both in vitro and in vivo, even during acute endotoxemia. These findings suggested that the alveolar epithelium, which secretes GM-CSF into the airway where it is required for alveolar macrophage maturation, likewise responds to GM-CSF priming in a receptor-mediated manner. In this study we determined that both the GM-CSF receptor alpha- and beta-subunits (GM-CSFRalpha and GM-CSFRbeta) are expressed throughout the rat airway epithelium and that this expression was significantly decreased in the alveolar epithelium following chronic ethanol ingestion (6 wk). In parallel, PU.1, the master transcription factor for GM-CSF signaling in hematopoietic cells, is also expressed in alveolar epithelial cells, and ethanol ingestion likewise decreased PU.1 protein expression and nuclear binding in the alveolar epithelium. Finally, GM-CSF signaling as reflected by PU.1 expression and nuclear binding was restored with recombinant GM-CSF treatment in vitro. We conclude that chronic ethanol ingestion decreases GM-CSF receptor expression and signaling in the lung epithelium. Consequently, we speculate that dampening of GM-CSF stimulation of the alveolar epithelium is responsible at least in part for the diverse functional defects that characterize the alcoholic lung and could be a therapeutic target in acute lung injury.

Multiple sclerosis (MS) is an immune-mediated disease that predominantly impacts the central nervous system (CNS). Animal models have been used to elucidate the underpinnings of MS pathology. One of the most well-studied models of MS is experimental autoimmune encephalomyelitis (EAE). This model was utilized to demonstrate that the cytokine granulocyte-macrophage colony-stimulating factor (GM-CSF) plays a critical and non-redundant role in mediating EAE pathology, making it an ideal therapeutic target. In this review, we will first explore the role that GM-CSF plays in maintaining homeostasis. This is important to consider, because any therapeutics that target GM-CSF could potentially alter these regulatory processes. We will then focus on current findings related to the function of GM-CSF signaling in EAE pathology, including the cell types that produce and respond to GM-CSF and the role of GM-CSF in both acute and chronic EAE. We will then assess the role of GM-CSF in alternative models of MS and comment on how this informs the understanding of GM-CSF signaling in the various aspects of MS immunopathology. Finally, we will examine what is currently known about GM-CSF signaling in MS, and how this has promoted clinical trials that directly target GM-CSF.

Defects in macrophage colony-stimulating factor (M-CSF) signaling disrupt myeloid cell differentiation in nonobese diabetic (NOD) mice, blocking myeloid maturation into tolerogenic antigen-presenting cells (APCs). In the absence of M-CSF signaling, NOD myeloid cells have abnormally high granulocyte macrophage colony-stimulating factor (GM-CSF) expression, and as a result, persistent activation of signal transducer/activator of transcription 5 (STAT5). Persistent STAT5 phosphorylation found in NOD macrophages is not affected by inhibiting GM-CSF. However, STAT5 phosphorylation in NOD bone marrow cells is diminished if GM-CSF signaling is blocked. Moreover, if M-CSF signaling is inhibited, GM-CSF stimulation in vitro can promote STAT5 phosphorylation in nonautoimmune C57BL/6 mouse bone marrow cultures to levels seen in the NOD. These findings suggest that excessive GM-CSF production in the NOD bone marrow may interfere with the temporal sequence of GM-CSF and M-CSF signaling needed to mediate normal STAT5 function in myeloid cell differentiation gene regulation.

Role of GM-CSF in regulating metabolism and mitochondrial functions critical to macrophage proliferation

BackgroundAdministration of granulocyte-macrophage colony stimulating factor (GM-CSF) relieves symptoms in Crohn's disease (CD). It has been reported that reduced GM-CSF bioactivity is associated with more aggressive ileal behaviour and that...

Granulocyte–Macrophage Colony-Stimulating Factor Is Essential for Normal Wound Healing

The current study was undertaken to evaluate the effects of granulocyte-macrophage colony-stimulating factor (GM-CSF) and cyclic AMP (cAMP) signaling interaction on human neutrophil apoptosis, either occurring spontaneously or induced by Fas antigen activation. Results show that GM-CSF, dibutyryl cAMP (a cAMP analog) and forskolin (an adenylate cyclase activator) are all able to suppress spontaneous neutrophil cell death. Of note however, when GM-CSF is used in combination with cAMP-elevating agents, an additive effect on neutrophil survival is observed with dibutyryl cAMP only, whereas supplementation of cell cultures with GM-CSF and forskolin results in a progressive reduction of antiapoptotic effects exerted by the single compounds. Moreover, although dibutyryl cAMP and forskolin do not affect Fas-triggered apoptotic events, they are still able to modulate the GM-CSF capacity to prolong neutrophil survival following anti-Fas IgM cell challenge, with effects similar to those respectively exerted on spontaneous neutrophil apoptosis. The data indicate that GM-CSF may negatively modulate the cAMP-mediated antiapoptotic pathway in human neutrophils, likely via the inhibition of adenylate cyclase activity. This would prevent an abnormal neutrophil survival as a result of cAMP signaling stimulation, which provides a novel insight into the role of GM-CSF as a physiological regulator of myeloid cell turnover.

RUNX1-ETO Expressing Hematopoietic Stem/Progenitor Cells (HSPCs) Display a Hypersensitivity To GM-CSF That Reduces Leukemogenic Potential

Unravelling synergistic immune interactions between respiratory virus infections and allergic airway inflammation.

The effect of pollutants on the immune system has filled tomes and is almost always controversial whether the topic is disinfectants in drinking water or particulates and lung cancer. Even whether outdoor and indoor air quality is improving or declining has been a source of considerable investigation, consultation and often litigation. Few areas, however, yield so much uncertainty and debate as the role of airborne pollutants in atopy. Atopy is defined as an immunoglobulin E- (IgE) mediated allergic response to environmental antigens and can be manifested as rhinitis, asthma or atopic dermatitis. While there is some debate over whether there has been a real increase in atopy over the last decades, it is indisputable that there has been a dramatic change over the last 200 years. While isolated cases of anaphylaxis had been noted before, allergies were unheard of until the early 19th century. Only 54 years after the first description of hay fever in England in 1819, it was considered an epidemic and a clear association with urbanization had been reported.1 What aspect of urbanization is involved has been much debated. There has been much discussion amongst both experimental immunologists and epidemiologists over whether pollutants are responsible for increased allergic sensitization and/or severity.2,3 In the last few years new studies have supported an alternative explanation, namely the decline in infectious diseases in industrialized countries.4,5 Does this ‘hygiene theory’ toll the death knell for the ‘pollution theory’? In this review I will argue that there is a compelling case to be made for both theories and that even this is not the entire picture.

We have examined the role of granulocyte-macrophage colony-stimulating factor (GM-CSF) in tumor-bearing BALB/c mice using the syngeneic F3II mammary carcinoma. In the present model, progression of subcutaneous tumors induced massive myelopoiesis in bone marrow and spleen due to GM-CSF secretion by tumor cells. In vitro, the addition of recombinant mouse GM-CSF (5– 25 ng/ml) caused a significant increase in F3II cell growth, either in the presence or absence of serum. Zymographic analysis of conditioned media from F3II monolayers showed that GM-CSF exerted a dose-dependent enhancement in the metalloproteinases MMP-9 (105 kD) and MMP-2 (70 kD), key enzymes in mammary tumor cell invasion. Our data suggest that ectopic GM-CSF production stimulates myelopoiesis and may also play an important role in tumor progression and metastasis formation.

Human neutrophils are rescued from apoptosis following incubation with once-washed, fibroblast-derived Toxoplasma gondii tachyzoites. Both infected and uninfected neutrophils are rescued, implicating a soluble mediator. In this study we investigated the origin and identity of this soluble mediator. Neutrophils were incubated either with purified tachyzoites or with conditioned medium derived from T. gondii-infected human fibroblasts. Conditioned medium was found to be a potent stimulus that delayed neutrophil apoptosis up to 72 h, whereas purified and extensively washed tachyzoites had no effect. Delayed apoptosis correlated with up-regulation of the neutrophil antiapoptotic protein, Mcl-1, and the neutrophil interleukin 3 receptor alpha subunit (IL-3Ralpha), suggesting a role for granulocyte-macrophage colony-stimulating factor (GM-CSF). GM-CSF and granulocyte colony-stimulating factor (G-CSF) were measurable in conditioned medium by enzyme-linked immunosorbent assay. Neutralizing antibodies to GM-CSF and G-CSF were additive in abrogating delayed neutrophil apoptosis induced by conditioned medium. Inhibitors of Src family tyrosine kinases, G(i) proteins, phosphatidylinositol 3-kinase, p44(erk1) and p42(erk2) mitogen-activated protein kinases, and Jak2 kinases partially attenuated the effect of conditioned medium, consistent with a role for G-CSF and/or GM-CSF. Hence, delayed neutrophil apoptosis is mediated by GM-CSF and G-CSF secreted by T. gondii-infected human fibroblasts. This enhanced neutrophil survival may contribute to the robust proinflammatory response elicited in the T. gondii-infected host.