NF-κB Regulates the LPS-Induced Expression of Interleukin 12 p40 in Murine Peritoneal Macrophages: Roles of PKC, PKA, ERK, p38 MAPK, and Proteasome

NF-κB plays a critical role in coordinating the control of gene expression during monocyte/macrophage activation. In this report we describe our investigation of the mechanisms of LPS-induced NF-κB activation and IL-12 expression in murine peritoneal suppressor macrophages. Treatment of these macrophages with LPS induced IκBα degradation and NF-κB activation. EMSAs demonstrated that NF-κB bound to a cis-acting element located in the murine IL-12 p40 promoter. LPS signal transduction has been shown to involve a variety of signal pathways. The results in this paper indicate that LPS-induced NF-κB binding activity was independent of PKC, PKA, ERK, and p38 MAPK, but was regulated by proteasome. Furthermore, Proteasome Inhibitor I abolished the LPS-induced mRNA expression of IL-12 p35 and p40, and SB203580 reduced these mRNA levels, whereas the blockade of PKC, PKA, and ERK had little effect. These data demonstrate that the LPS-induced activation of proteasome · IκB · NF-κB and p38 MAPK signal pathways regulate the IL-12 expression in murine peritoneal suppressor macrophages.