Induction of Multiple Cytokine Gene Expression and IRF-1 mRNA by Flavone Acetic Acid in a Murine Macrophage Cell Line

Flavone-8-acetic (FAA) acid is a potential chemotherapeutic agent that has demonstrated strong immunomodulatory activity in murine model systems. The immunomodulatory activity of this drug in murine systems has been linked to its ability to rapidly induce cytokine gene expression in vivo and in mouse splenocytes ex vivo. We have now developed a tissue culture model for studying the molecular basis of induction of cytokine expression by FAA. Using the mouse macrophage cell line, ANA-1, we can demonstrate the direct induction of interferon β (IFNβ), interleukin-6 (IL-6), tumor necrosis factor-α (TNFα), and interferon response factor-1 (IRF-1) mRNA expression following treatment with FAA. Furthermore, the induction of the IFNβ mRNA can occur in the absence of new protein synthesis. Nuclear run-on experiments indicate that at least part of the induction of IFNβ, IL-6, and TNFα mRNA occurs at the transcriptional level while the increase in IRF-1 mRNA appears largely post-transcriptional or due to the production of IFNβ protein. Additionally, experiments using agents that interfere with second messengers demonstrate that activation of the protein kinase C pathway is possibly involved in FAA gene induction. The use of this tissue culture model system should lead to a more complete understanding of the mechanisms involved in FAA-induced gene expression and help determine why this drug is inactive on human cells.