Suppression of NF-κB activity by sulfasalazine is mediated by direct inhibition of IκB kinases α and β

• DOI: 10.1053/gast.2000.19458
• Publication Date: 2005-07-29T17:58:00Z
• Authors: Christoph K. Weber; Susanne Liptay; Thomas Wirth; Guido Adler; Roland M. Schmid
• Keywords: 0301 basic medicine; 03 medical and health sciences; 3. Good health

Abstract Background & Aims: Activation of NF-κB/Rel has been implicated in the pathogenesis of inflammatory bowel disease (IBD). Various drugs used in the treatment of IBD, such as glucocorticoids, 5-aminosalicylic acid, and sulfasalazine, interfere with NF-κB/Rel signaling. The aim of this study was to define the molecular mechanism by which sulfasalazine inhibits NF-κB activation. Methods: The effects of sulfasalazine and its moieties on NF-κB signaling were evaluated using electromobility shift, transfection, and immune complex kinase assays. The direct effect of sulfasalazine on IκB kinase (IKK) activity was investigated using purified recombinant IKK-α and -β proteins. Results: NF-κB/Rel activity induced by tumor necrosis factor α, 12- O -tetradecanoylphorbol-13-acetate, or overexpression of NF-κB–inducing kinase, IKK-α, IKK-β, or constitutively active IKK-α and IKK-β mutants was inhibited dose dependently by sulfasalazine. Sulfasalazine inhibited tumor necrosis factor α–induced activation of endogenous IKK in Jurkat T cells and SW620 colon cells, as well as the catalytic activity of purified IKK-α and IKK-β in vitro. In contrast, the moieties of sulfasalazine, 5-aminosalicylic acid, and sulfapyridine or 4-aminosalicylic acid had no effect. Activation of extracellular signal-related kinase (ERK) 1 and 2, c-Jun-N-terminal kinase (JNK) 1, and p38 was unaffected by sulfasalazine. The decrease in substrate phosphorylation by IKK-α and -β is associated with a decrease in autophosphorylation of IKKs and can be antagonized by excess adenosine triphosphate. Conclusions: These data identify sulfasalazine as a direct inhibitor of IKK-α and -β by antagonizing adenosine triphosphate binding. The suppression of NF-κB activation by inhibition of the IKKs contributes to the well-known anti-inflammatory and immunosuppressive effects of sulfasalazine. GASTROENTEROLOGY 2000;119:1209-1218