Abstract
The action of interleukin-1 alpha (IL-1α) and tumor necrosis factor alpha (TNFα) on the production of biologically active granulocyte colony-stimulating factor (G-CSF) and granulocyte-macrophage colony-stimulating factor (GM-CSF) was studied and the secretion into the supernatant of human endothelial cell cultures was quantified by enzyme-linked immunosorbent assay (ELISA). In unstimulated endothelial cells low concentrations of G-CSF and GM-CSF were measured by ELISA. Stimulation for 24 h with either IL-1α or TNFα caused a concentration-dependent increase of both colony stimulating factors in the supernatant. Range of IL-1α studied: 0.1–100 U/ml; maximum CSF induced: G-CSF 142 + 16 ng/6 × 105 cells, GM-CSF 18.5 ± 3.3 ng/6 × 105 cells. Range of TNFα studied: 10–2000 U/ml. 4 maximum CSF induced: G-CSF: 36 ± 6 ng/6 × 105 cells, GM-CSF 16.7 ± 1.5 ng/6 × 10 cells. The dosages of both factors were varied to study the combined action of IL-1α and TNFα on CSF production. IL-1α (0.1–10 U/ml) combined with TNFa (10–1000 U/ml) enhanced the effect onCSFproductionina superadditivemannercomparedwith theeffect of TNFaorIL-1α alone. Higher concentrations of IL-1α (10 U/ml) with TNFa (10–1000 U/ml) inhibited G-CSF production but not GM-CSF production. IL-1α was more potent as an inducer of G-CSF than TNFa at doses approximately equipotent in causing GM-CSF production in human endothelial cells. Quantitative determination of G-CSF and GM-CSF revealed that the production of these CSFs was differently regulated by IL-1α and TNFα and demonstrated a superadditive effect by the two cytokines on G-CSF and GM-CSF production.