Interleukin-12 (IL-12) and IL-23 Induction of Substance P Synthesis in Murine T Cells and Macrophages Is Subject to IL-10 and Transforming Growth Factor Regulation

Substance P is a tachykinin that enhances pathways of inflammation. Leukocytes at sites of intestinal inflammation make substance P. This study explored the role of interleukin-12 (IL-12), IL-23, and the regulatory cytokines IL-10 and transforming growth factor (TGF) in controlling leukocyte substance P production. In murine schistosomiasis, it was found that IL-12 and IL-23 drive substance P gene expression and peptide synthesis in murine splenic T cells and macrophages, respectively. Cytokine induction of substance P synthesis both in T cells and in macrophages depends on intracellular NFB activation and is Stat4 independent. IL-10 inhibits T-cell substance P production, while TGFblocks macrophage substance P expression. Intestinal macrophages also produce substance P, subject mostly to IL-23 and TGFregulation. Hemokinin is another tachykinin with homology to substance P. Macrophages and T cells make hemokinin, but hemokinin production is not subject to IL-12 or IL-23 regulation.