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

Abstract

IL-1beta stimulation of cultured epithelial cells induces the degradation of IkappaBalpha and the consequent nuclear translocation of NF-lambdaB, 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-kappaB 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-kappaB activation. Similarly, scavenging of free radicals and oxidants by pyrrolidine dithiocarbamate and dimethyl sulfoxide did not block IL-1beta-induced IkappaBalpha degradation and NF-kappaB activation. Genistein, a nonspecific tyrosine kinase inhibitor, also had no effect on IL-1beta-mediated effects on NF-kappaB. Serine protease inhibition by tosyl-lysine-chloromethylketone and tosyl-phenylalanine-chloromethylketone inhibited IkappaBalpha degradation and NF-kappaB activation stimulated by IL-1beta. Our data highlight the strong divergence between epithelial and mononuclear cells in the signal transduction pathways relating IL-1beta stimulation and NF-kappaB nuclear translocation.