Human primary bone marrow cells secret various cytokines upon stimulation with lipopolysaccharide (LPS). This study demonstrated that LPS-mediated cytokine secretion can be affected by all-trans retinoic acid (t-RA). t-RA stimulated LPS-mediated granulocyte colony stimulating factor (G-CSF) secretion over two-fold and inhibited both LPS-mediated granulocyte-macrophage CSF (GM-CSF) and tumor necrosis factor alpha (TNFalpha) secretion by as much as 50%. The stimulation of t-RA on LPS-mediated G-CSF secretion was dose-dependent and was observed at t-RA concentration of as low as 10(-10) M. Some other retinoids were also as effective as t-RA, whereas other steroids were either less or not effective or inhibitory on LPS-mediated G-CSF secretion. Further experiments indicated that interleukin 1 (IL-1), one of the mediators of LPS activity, also synergized with t-RA to stimulate G-CSF secretion. These observations suggest that there is a convergence of IL-1 and t-RA signal transduction pathways in G-CSF release by bone marrow cells.

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