Abstract
Granulocyte colony-stimulating factor (G-CSF) selectively stimulates proliferation and differentiation of neutrophil progenitors which play important roles in host defense against infectious agents. However, persistent G-CSF production often leads to neutrophilia and excessive inflammatory reactions. There is therefore a need to understand the mechanism regulating G-CSF expression. In this study, we showed that U0126, a MEK1/2 inhibitor, decreases lipopolysaccharide (LPS)-stimulated G-CSF promoter activity, mRNA expression and protein secretion. Using short hairpin RNA knockdown, we demonstrated that ERK2, and not ERK1, involves in LPS-induced G-CSF expression, but not LPS-regulated expression of TNF-α. Reporter assays showed that ERK2 and C/EBPβ synergistically activate G-CSF promoter activity. Further chromatin immunoprecipitation (ChIP) assays revealed that U0126 inhibits LPS-induced binding of NF-κB (p50/p65) and C/EBPβ to the G-CSF promoter, but not their nuclear protein levels. Knockdown of ERK2 inhibits LPS-induced accessibility of the G-CSF promoter region to DNase I, suggesting that chromatin remodeling may occur. These findings clarify that ERK2, rather than ERK1, mediates LPS-induced G-CSF expression in macrophages by remodeling chromatin, and stimulates C/EBPβ-dependent activation of the G-CSF promoter. This study provides a potential target for regulating G-CSF expression.
Highlights
Granulocyte colony-stimulating factor (G-CSF), a hematopoietic growth factor, regulates the proliferation of neutrophil progenitors, and the differentiation of granulocyte lineages, and the survival and maturation of neutrophil progenitors, and their mobilization from bone marrow to peripheral tissues [1]
We have previously reported that pretreatment with rapamycin, which blocks the activity of mTOR complex 1, inhibits LPS-induced G-CSF expression by decreasing the expression of octamer-binding factor 2 (Oct-2), a crucial transcription factor required for this process [6]
Since LPS is known to increase G-CSF mRNA expression in mouse bone marrow-derived macrophage (BMDMs), we examined whether the ERK inhibitors U0126 or PD98059 could block this effect in primary cells
Summary
Granulocyte colony-stimulating factor (G-CSF), a hematopoietic growth factor, regulates the proliferation of neutrophil progenitors, and the differentiation of granulocyte lineages, and the survival and maturation of neutrophil progenitors, and their mobilization from bone marrow to peripheral tissues [1]. Recombinant G-CSF has been widely used in patients receiving chemotherapy to increase the number of circulating hematopoietic progenitor cells and in certain patients with neutropenia. Endogenous G-CSF is produced by various types of PLOS ONE | DOI:10.1371/journal.pone.0129685. ERK2 Mediates LPS-Stimulated G-CSF Expression in Macrophages Endogenous G-CSF is produced by various types of PLOS ONE | DOI:10.1371/journal.pone.0129685 June 26, 2015
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