Inflammatory cytokine levels are influenced by interactions between THP-1 monocytic, U-373 MG astrocytic, and SH-SY5Y neuronal cell lines of human origin.

We measured the secretion of interleukin (IL)1beta, IL-6 and tumor necrosis factor-alpha (TNF-alpha) from human monocytic (THP-1), astrocytic (U-373 MG) and neuronal (SH-SY5Y) cell lines alone and in co-culture, with and without stimulation by a combination of lipopolysaccharide (LPS) plus interferon-gamma (IFN-gamma) or amyloid beta peptide 1-40 (Abeta). LPS+IFN-gamma stimulation increased IL-1beta secretion 16-fold from THP-1 cells. It increased IL-6 secretion 23-fold from THP-1 cells and 2.5-fold from U-373 MG cells. It increased TNF-alpha secretion 3.4-fold from THP-1 cells, but did not influence its secretion from U-373 MG cells. It did not affect the secretion of any of the cytokines from SH-SY5Y cells. Abeta stimulation increased IL-6 secretion 2.3-fold from U-373 MG cells but did not influence secretion of IL-1beta or TNF-alpha. Abeta stimulation also failed to influence secretion of any of the cytokines from THP-1 or SH-SY5Y cells. When THP-1 and U-373 MG cells were cocultured, IL-1beta and IL-6 secretion, but not TNF-alpha secretion, were significantly reduced from the levels obtained in independent cultures, suggesting that a mutual suppressive action may occur between microglia and astrocytes.