IL-1β induction of NF-κB activation in human intestinal epithelial cells is independent of oxyradical signaling

IL-1β stimulation of cultured epithelial cells induces the degradation of IκBα and the consequent nuclear translocation of NF-λB, a critical proinflammatory transcription factor in the mucosal host immune response. The role of reactive oxygen intermediates, serine protease activity, and tyrosine kinase activity in the activation of NF-κB is weakly conserved across various cell lineages and has not been defined in human enterocytes, a major target of oxidant stress in sepsis, thermal injury, and hemorrhagic shock. We report here that in Caco-2BBe cells, a transformed human colon cancer cell line with features of small intestinal epithelial cells in culture, exposure to oxidant stress (hydrogen peroxide 1-10 mM) did not induce NF-κB activation. Similarly, scavenging of free radicals and oxidants by pyrrolidine dithiocarbamate and dimethyl sulfoxide did not block IL-1β-induced IκBα degradation and NF-κB activation. Genistein, a non-specific tyrosine kinase inhibitor, also had no effect on IL-1β-mediated effects on NF-κB. Serine protease inhibition by tosyl-lysine-chloromethylketone and tosyl-phenylalanine-chloromethylketone inhibited IκBα degradation and NF-κB activation stimulated by IL-1β. Our data highlight the strong divergence between epithelial and mononuclear cells in the signal transduction pathways relating IL-1β stimulation and NF-κB nuclear translocation.