Experiments proposed in this application will explore the role of macrophage activation in the pathogenesis[unreadable] of the inflammatory bowel diseases (IBD). We will focus on the molecular regulation of IL-12 p40 in[unreadable] macrophages as one of the most biologically significant events in T-helper1 (Th1)-mediated chronic[unreadable] inflammation. We have recently described a novel composite element in the IL-12 p40 promoter that[unreadable] interacts with members of the nuclear factor of activated T cells (NFAT) and interferon regulatory factor (IRF)[unreadable] families of transcription factors. This control element is involved in the synergistic induction of IL-12 p40[unreadable] promoter activity by bacterial products and interferon-y (IFN-y), and is an important target for inhibition of IL-[unreadable] 12 p40 gene expression through several signal transduction pathways.[unreadable] The overall goal of this proposal is to understand the molecular regulation of IL-12 p40 in experimental[unreadable] models of IBD. Experiments will elucidate the role of two newly appreciated anti-inflammatory signal[unreadable] transduction pathways in macrophages: Heme oxygenase-1 (HO-1) and phosphatidylinositol-3-kinase[unreadable] (PI3K). We hypothesize that these anti-inflammatory pathways converge through regulation of NFAT/IRF[unreadable] interactions at the IL-12 p40 promoter. By inhibiting IL-12 p40, HO-1 and PI3K serve as molecular "brakes"[unreadable] for macrophage activation that may limit the extent and duration of chronic intestinal inflammation.[unreadable] lnterleukin-12 (IL-12) is an inflammatory protein that has been demonstrated to be important in the[unreadable] progression of human Crohn's disease (CD). In this application, we will test therapeutic interventions in[unreadable] mouse models of CD to inhibit IL-12 production by cells of the immune system called macrophages. Studies[unreadable] in this application will give us important information about immune inhibitory pathways that may be defective[unreadable] in human IBD and may lead to new therapeutic interventions in human IBD that target macrophages and IL-[unreadable] 12.[unreadable]