Lipid Droplet Formation in Human Myeloid NB4 Cells Stimulated by All Trans Retinoic Acid and Granulocyte Colony-Stimulating Factor: Possible Involvement of Peroxisome Proliferator-Activated Receptor γ

Abstract

All trans retinoic acid (ATRA), a differentiation inducer for human myeloid NB4 cells, induced accumulation of lipid droplet as determined by positivity of Nile Red and Oil Red O in this cell line. Granulocyte colony-stimulating factor (G-CSF), although not having detectable effect by itself, exerted the additive effects on lipid droplet formation in NB4 cells when combined with ATRA. mRNA analysis for peroxisome proliferator-activated receptors (PPARs) revealed the initial transient downregulation followed by upregulation of the transcript for PPARγ2, a master molecule for adipogenesis, and upregulation of PPARα. BADGE, a synthetic antagonist for PPARγ, potently inhibited lipid droplet formation in NB4 cells stimulated by ATRA and/or G-CSF, but not the functional differentiation of the cells by ATRA and/or G-CSF. These results suggest that ATRA and G-CSF induce lipid droplet formation via certain PPARγ-mediated specific mechanisms in human myeloid NB4 cells during functional differentiation.