Tumor necrosis factor type α stimulates human endothelial cells to produce granulocyte/macrophage colony-stimulating factor

Tumor necrosis factor type α (TNF-α) is produced by monocytes and has been purified, sequenced, and cloned from the HL-60 cell line. Soluble products of monocytes stimulate endothelial cells to release multilineage hematopoietic colony-stimulating activity. To determine whether TNF-α could stimulate endothelial cells to produce these activities, we added recombinant human TNF-α to cultured human umbilical vein endothelial cells. Untreated endothelial cell conditioned medium and TNF-α-stimulated endothelial cell conditioned medium were tested for hematopoietic colony stimulating activity in colony-forming assays in methylcellulose. TNF-α stimulated growth factor production by endothelial cells. Fifth-passage human endothelial cells and multiply-passaged bovine aortic endothelial cells responded similarly to first-passage endothelial cells, indicating that the action of TNF-α on endothelial cells is direct and not due to contaminating lymphocytes or monocytes present in the first-passage cultures. To investigate the molecular basis for these findings, polyadenylylated RNA was prepared from the TNF-α-stimulated endothelial cells and probed for granulocyte-macrophage colony-stimulating factor and granulocyte colony-stimulating factor mRNA. Granulocyte-macrophage colony-stimulating factor, but not granulocyte colony-stimulating factor, message was detected. This finding suggests that at least some of the hematopoietic colony-stimulating activity released by the TNF-α-stimulated endothelial cells is granulocyte-macrophage colony-stimulating factor. These results demonstrate that a purified monocyte product can stimulate endothelial cells to produce the multilineage growth factor granulocyte-macrophage colony-stimulating factor and extend the role of this immuno-regulatory protein to the regulation of hematopoiesis in vitro.