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Transcriptional and post-transcriptional regulation of GM-CSF-induced IL-1 beta gene expression in PMN
M C Fernandez1, J Walters, P Marucha
1Department of Medical Microbiology and Immunology, College of Medicine, Ohio State University, Columbus 43210, USA.
Abstract:
Polymorphonuclear leukocytes (PMN) play an important role in inflammation, immune responses, and tissue repair by secreting interleukin- 1 beta (IL-1 beta). We investigated the regulation of IL-1 beta gene expression in human PMN treated with granulocyte-macrophage colony-stimulating factor (GM-CSF). GM-CSF induced IL-1 beta mRNA accumulation at 0.1 ng/ml and maximal induction was observed at 1 ng/ml. IL- 1 beta mRNA levels reached a maximum with 1-2 h after stimulation with GM-CSF and returned to baseline levels by 4-6 h. The time course of IL-1 beta mRNA induction by GM-CSF was more protracted than previously reported for PMN stimulated with tumor necrosis factor-alpha (TNF-alpha, 10 ng/ml). Nuclear run-on analysis indicated that GM-CSF, like TNF, increases IL-1 beta transcription. Kinetic studies with the RNA synthesis inhibitor, actinomycin D, showed that GM-CSF induces stable IL-1B mRNA. Cycloheximide enhanced the IL-1 beta mRNA accumulation by GM-CSF at the level of mRNA stabilization, but blocked IL-1 beta mRNA expression by TNF. Thus, GM-CSF increases IL-1 beta message accumulation in PMN at both the transcriptional and post-transcriptional levels by mechanisms that are different from TNF induction of IL-1 beta gene expression.
Insights
Granulocyte-macrophage colony-stimulating factor (GM-CSF) boosts interleukin-1 beta (IL-1 beta) gene expression in human polymorphonuclear leukocytes (PMN). GM-CSF enhances IL-1 beta mRNA through both transcriptional and post-transcriptional mechanisms, distinct from TNF-alpha.
Area of Science:
- Immunology
- Molecular Biology
- Cell Biology
Background:
- Polymorphonuclear leukocytes (PMN) are crucial in inflammation and immune responses, secreting interleukin-1 beta (IL-1 beta).
- Understanding the regulation of IL-1 beta gene expression in PMN is vital for inflammatory disease research.
Purpose of the Study:
- To investigate how granulocyte-macrophage colony-stimulating factor (GM-CSF) regulates IL-1 beta gene expression in human PMN.
- To compare the mechanisms of IL-1 beta induction by GM-CSF with those of tumor necrosis factor-alpha (TNF-alpha).
Main Methods:
- Human PMN were treated with varying concentrations of GM-CSF.
- IL-1 beta mRNA accumulation and stability were assessed using techniques like nuclear run-on assays and actinomycin D treatment.
- The role of protein synthesis in IL-1 beta mRNA regulation was studied using cycloheximide.
Main Results:
- GM-CSF induced IL-1 beta mRNA accumulation in a dose-dependent manner, with maximal induction at 1 ng/ml.
- IL-1 beta mRNA levels peaked at 1-2 hours post-stimulation and returned to baseline by 4-6 hours.
- GM-CSF increased IL-1 beta transcription and stabilized IL-1 beta mRNA, with cycloheximide enhancing this stabilization.
Conclusions:
- GM-CSF upregulates IL-1 beta gene expression in human PMN at both transcriptional and post-transcriptional levels.
- The mechanisms by which GM-CSF induces IL-1 beta are distinct from those of TNF-alpha.
- These findings provide insights into the complex regulation of inflammatory mediators by cytokines.