Regulation of tumor necrosis factor expression in a macrophage-like cell line by lipopolysaccharide and cyclic AMP.

Bacterial lipopolysaccharide (LPS, 1 microgram/ml) induced the rapid production of tumor necrosis factor (TNF-alpha) mRNA in the RAW264 macrophage-like cell line. TNF-alpha mRNA peaked within 45 min of LPS treatment and remained high for greater than 3 hr. Transcription of TNF-alpha mRNA was increased within 15 min of LPS treatment. The quantity of TNF-alpha mRNA in LPS-stimulated cells was reduced to basal levels by treatment with cAMP, cAMP analogs, or agents which raise intracellular cAMP. This was not a general effect on all mRNA levels as the expression of a second gene, ornithine decarboxylase, was enhanced by cAMP treatment. cAMP did not have an effect on the stability of TNF-alpha mRNA. This is in contrast to the protein synthesis inhibitor, cycloheximide, which leads to a stabilization of TNF-alpha mRNA. Our results suggest that the primary regulation of tumor necrosis factor by cAMP and LPS occurs at the transcriptional level.