Role of NF- B in transcriptional regulation of the phagocyte NADPH oxidase by tumor necrosis factor-

Macrophages play an important role in the pathogenesis of chronic inflammatory disease. Activation of these phagocytes induces the production of proinflammatory cytokines, such as IL-1 and TNFand the generation of reactive oxygen species (ROS), such as superoxide anion (O2 •–). Recently, we found that TNFtreatment of human monocytic cells (MonoMac1) and isolated human monocytes resulted in up-regulation of the NADPH oxidase gene, neutrophil cytosolic factor 2 (NCF2). These results suggested that TNF, produced by activated macrophages, could serve as an autocrine/paracrine regulator of the oxidase, resulting in increased and/or prolonged production of O2 •–. To gain a better understanding of the mechanisms involved in NADPH oxidase regulation by TNF, we evaluated transcriptional regulation of oxidase genes in MonoMac1 cells and human monocytes. We show that TNF-treated cells have increased levels of mRNA and up-regulated expression of NADPH oxidase subunits p47, p67, and gp91, as well as increased oxidase activity. Pharmacological inhibitors of NFB activation blocked TNF-induced up-regulation of NCF1, NCF2, and CYBB message, which correlated with a reduction in expression of the corresponding oxidase proteins and decreased O2 •– production. These data demonstrate that the increase in and/or maintenance of O2 •– production in TNF-treated MonoMac1 cells and monocytes are a result, in part, of transcriptional up-regulation of three essential NADPH oxidase genes via the NFB pathway. This novel finding supports a model, whereby TNF-dependent activation of NFB up-regulates phagocyte NADPH oxidase activity, leading to enhanced ROS production and further NFB activation, potentially contributing to sustained oxidant production in chronic inflammation. J. Leukoc. Biol. 82: 000–000; 2007.