Tumor necrosis factor-alpha (TNF) is a macrophage-derived peptide that is known to be an important mediator in various physiologic and immunologic events. Although the effector function of TNF has received recent attention, there is relatively little information regarding factors that regulate TNF expression. Highly Ia-positive murine peritoneal macrophages obtained via complete Freund's adjuvant elicitation were challenged with lipopolysaccharide (LPS) and assessed for the production and regulation of TNF at the cellular and molecular levels. In response to 1 microgram/ml LPS, the kinetics of functionally active TNF reached a maximum at approximately 3-4 h. The plateau in TNF levels was concomitant with an accelerated increase in prostaglandin E2 production. The addition of exogenous PGE2 demonstrated a dose-dependent reduction in LPS-induced TNF activity at the cellular level, as well as a significant reduction in TNF mRNA accumulation as assessed by Northern blot and in situ hybridization analysis. The reduction in LPS-stimulated mRNA accumulation by PGE2 was shown to occur at least at the level of transcription, since nuclear run-off analysis showed a specific reduction in TNF transcripts. These studies demonstrate that PGE2 can regulate macrophage-derived TNF gene expression.