Differential transcriptional and posttranscriptional regulation of gene expression of the colony-stimulating factors by interleukin-1 and fetal bovine serum in murine fibroblasts

Abstract

Colony-stimulating factors (CSF) are important factors in the proliferation and differentiation of hematopoietic progenitor cells (HPC), and in the survival and activation of mature blood cells. Interleukin-1 (IL-1) combined with fetal bovine serum (FBS) strongly induces the expression of macrophage-CSF (M-CSF), granulocyte-CSF (G- CSF), and granulocyte-macrophage-CSF (GM-CSF) in fibroblasts. Here, we report on the regulation of CSF gene expression in murine fibroblasts following IL-1 and FBS stimulation. We demonstrate that 10T1/2 murine fibroblasts induced by FBS or IL-1 accumulate M-CSF messenger RNA (mRNA). G-CSF mRNA expression was induced by IL-1, and not by FBS. For GM-CSF expression, induction with both FBS and IL-1 was required. Blocking studies with actinomycin-D showed that active transcription is essential for accumulation of all three CSF mRNAs. After blocking protein synthesis with cycloheximide, IL-1- or FBS-induced M-CSF expression and IL-1 plus FBS-induced GM-CSF expression still occurred and was increased. IL-1-induced G-CSF expression was completely prevented in these cells by pretreatment with cycloheximide, illustrating that, for this effect, intermediate protein synthesis was required. The half-lives of M-CSF transcripts were not substantially altered by addition of IL-1, FBS, or FBS plus IL-1. Using nuclear run- on assays, we demonstrated that the transcription rate of M-CSF was increased up to 20-fold by the addition of FBS, IL-1, or FBS plus IL-1. After blocking protein synthesis with cycloheximide, IL-1-or FBS- induced increase in M-CSF transcription rate was also observed. GM-CSF transcription increased up to fourfold after induction with FBS or IL- 1. G-CSF transcription rate was not altered by FBS or IL-1. Our results indicate that M-CSF expression induced by FBS or IL-1 in these fibroblasts is primarily regulated at the transcriptional level. GM-CSF expression appears to be regulated both transcriptionally and posttranscriptionally, and G-CSF expression is regulated mainly at the posttranscriptional level.

Rapamycin inhibits lipopolysaccharide induction of granulocyte‐colony stimulating factor and inducible nitric oxide synthase expression in macrophages by reducing the levels of octamer‐binding factor‐2

“…Although recombinant G‐CSF is routinely used to treat neutropenia and to mobilize hematopoietic stem cells from the bone marrow into the peripheral blood before transplantation [31], it is also expressed endogenously in a variety of cell types in response to treatment with LPS, tumor necrosis factor‐α, interleukin‐1β, PMA or interferon‐γ [32]. Expression of G‐CSF can be regulated at both the transcriptional and post‐transcriptional levels [33]; however, the regulatory mechanisms are poorly understood. To our knowledge, this is the first study showing that rapamycin reduces the LPS‐induced expression of G‐CSF at the transcriptional level in macrophages by blocking mTOR activity.…”

Granulocyte colony-stimulating factor: Molecular mechanisms of action during steady state and ‘emergency’ hematopoiesis

“…This in turn stimulates neutrophil production in the bone marrow and neutrophil mobilization to the peripheral circulation. The synthesis of G-CSF appears to be controlled via post-transcriptional and transcriptional mechanisms [46,47]. The G-CSF promoter contains binding sites for NF-κB p65 and NF-IL6/C/EBPβ [48], which are well-characterized transcription factors that participate in many inflammatory and immune 'stress' response pathways.…”

Is interleukin 17, an inducible cytokine that stimulates production of other cytokines, merely a redundant player in a sea of other biomolecules?

“…These effects can be direct on the stem or progenitor cells them-selves, actions which are most rigorously determined in vitro with an initial culture of a single isolated stem or progenitor cell (14)(15)(16), or the effects can be indirectly mediated. This latter effect involves accessory cells which can be induced by a number of stimuli, including cytokines, to produce and release a single, but more likely a group of cytokines (1)(2)(3)(4)(5)(6)(7)(17)(18)(19)(20)(21)(22)(23) which can then directly act on stem or progenitor cells or have a cascading effect on induction of the production or release of additional cytokines or other biologically active molecules.…”