Electronegative L5-LDL induces the production of G-CSF and GM-CSF in human macrophages through LOX-1 involving NF-κB and ERK2 activation

Atherosclerosis. 2017 Dec;267:1-9. doi: 10.1016/j.atherosclerosis.2017.10.016. Epub 2017 Oct 14.

Abstract

Background and aims: Circulating levels of granulocyte colony-stimulating factor (G-CSF) and granulocyte macrophage colony-stimulating factor (GM-CSF) are associated with the severity of acute myocardial infarction (AMI). However, what causes increases in G-CSF and GM-CSF is unclear. In this study, we investigated whether L5-low-density lipoprotein (LDL), a mildly oxidized LDL from AMI, can induce G-CSF and GM-CSF production in human macrophages.

Methods: L1-LDL and L5-LDL were isolated through anion-exchange chromatography from AMI plasma. Human macrophages derived from THP-1 and peripheral blood mononuclear cells were treated with L1-LDL, L5-LDL, or copper-oxidized LDL (Cu-oxLDL) and G-CSF and GM-CSF protein levels in the medium were determined. In addition, the effects of L5-LDL on G-CSF and GM-CSF production were tested in lectin-type oxidized LDL receptor-1 (LOX-1), CD36, extracellular signal-regulated kinase (ERK) 1, and ERK2 knockdown THP-1 macrophages.

Results: L5-LDL but not L1-LDL or Cu-oxLDL significantly induced production of G-CSF and GM-CSF in macrophages. In vitro oxidation of L1-LDL and L5-LDL altered their ability to induce G-CSF and GM-CSF, suggesting that the degree of oxidation is critical for the effects. Knockdown and antibody neutralization experiments suggested that the effects were caused by LOX-1. In addition, nuclear factor (NF)-κB and ERK1/2 inhibition resulted in marked reductions of L5-LDL-induced G-CSF and GM-CSF production. Moreover, knockdown of ERK2, but not ERK1, hindered L5-LDL-induced G-CSF and GM-CSF production.

Conclusions: The results indicate that L5-LDL, a naturally occurring mild oxidized LDL, induced G-CSF and GM-CSF production in human macrophages through LOX-1, ERK2, and NF-κB dependent pathways.

Keywords: Electronegative LDL; Granulocyte colony-stimulating factor (G-CSF); Granulocyte macrophage colony-stimulating factor (GM-CSF); Lectin-type oxidized LDL receptor-1 (LOX-1); Macrophage.

MeSH terms

  • Cell Line
  • Culture Media
  • Gene Expression Regulation
  • Granulocyte Colony-Stimulating Factor / biosynthesis*
  • Granulocyte-Macrophage Colony-Stimulating Factor / biosynthesis*
  • Humans
  • Lipoproteins, LDL / pharmacology*
  • MAP Kinase Signaling System
  • Macrophages / metabolism
  • Mitogen-Activated Protein Kinase 1 / genetics
  • Mitogen-Activated Protein Kinase 1 / metabolism*
  • NF-kappa B p50 Subunit / genetics
  • NF-kappa B p50 Subunit / metabolism*
  • ST Elevation Myocardial Infarction / blood
  • Scavenger Receptors, Class E / genetics
  • Scavenger Receptors, Class E / metabolism*
  • Signal Transduction

Substances

  • Culture Media
  • Lipoproteins, LDL
  • NF-kappa B p50 Subunit
  • NFKB1 protein, human
  • OLR1 protein, human
  • Scavenger Receptors, Class E
  • low-density lipoprotein L5, human
  • Granulocyte Colony-Stimulating Factor
  • Granulocyte-Macrophage Colony-Stimulating Factor
  • MAPK1 protein, human
  • Mitogen-Activated Protein Kinase 1