A similar phenotype is observed in mice lacking both the IκB kinase α (IKKα) and IKKβ subunits in intestinal epithelial cells (IKKα\βΔIEC), and mice lacking the NF-κB subunit RelA in intestinal epithelial cells are hypersensitive to DSS-induced colitis [4, 10]. Toll-like receptors (TLRs)

are the key sensors of microbial products in innate immunity and appear to be critical in initiating NF-κB activation in intestinal epithelial cells. Thus, mice lacking myeloid differentiation primary response gene 88 (MyD88), a key component downstream of a number of TLRs, are also hyper-responsive to DSS-induced colitis [11, 12]. Together, these studies indicate that while NF-κB activity this website is critical for inflammation in IBD, NF-κB activity in the epithelium is critical for tissue homeostasis and its inhibition can have severe consequences, including the development of IBD. Thus, a further understanding of the regulation of NF-κB during inflammation in the intestine and the contribution of components of the NF-κB pathway

to inflammation and epithelial proliferation in the mucosa are critical for the development of effective therapies for IBD. Bcl-3 is a member of the IκB family of proteins, as determined by sequence homology and the presence of ankyrin repeat domains which mediate interaction with NF-κB dimers [13-15]. Bcl-3 is largely a nuclear protein, and binds only homodimers of the CHIR-99021 order p50 or p52 NF-κB subunits [14]. Interestingly, these two subunits lack a transactivation domain and thus have been regarded generally as repressors of NF-κB transcription when present in the homodimeric form. Bcl-3 is an essential negative regulator of TLR-induced responses. Bcl-3−/− macrophages and mice are hyper-responsive

to TLR stimulation, and are defective in lipopolysaccharide tolerance [16]. Recently, a single nucleotide polymorphism (SNP) associated with reduced Bcl-3 gene expression has been identified as a potential risk factor for Crohn’s disease (CD) [17]. However, the role of Bcl-3 in IBD has not been investigated to date. In this study we report that our measurements of Bcl-3 mRNA in patient groups with CD, ulcerative colitis (UC) and healthy individuals reveal elevated Bcl-3 expression associated with IBD, in contrast to the predictions of Metformin price the single nucleotide polymorphism (SNP) analysis [17]. To explore further the potential role of Bcl-3 in IBD we used the DSS-induced model of colitis in Bcl-3−/− mice. Considering the previously described anti-inflammatory role of Bcl-3, we were surprised to find that Bcl-3−/− mice were less sensitive to DSS-induced colitis. Measurement of the inflammatory response in the colon by analysis of the expression levels of proinflammatory cytokines and the recruitment of T cells, neutrophils, macrophage and dendritic cells revealed no significant differences between DSS-treated Bcl-3−/− and wild-type mice.