IL-1β causes an increase in intestinal epithelial tight junction permeability

IL-1 beta is a prototypical proinflammatory cytokine that plays a central role in the intestinal inflammation amplification cascade. Recent studies have indicated that a TNF-alpha- and IFN-gamma-induced increase in intestinal epithelial paracellular permeability may be an important mechanism contributing to intestinal inflammation. Despite its central role in promoting intestinal inflammation, the role of IL-1 beta on intestinal epithelial tight junction (TJ) barrier function remains unclear. The major aims of this study were to determine the effect of IL-1 beta on intestinal epithelial TJ permeability and to elucidate the mechanisms involved in this process, using a well-established in vitro intestinal epithelial model system consisting of filter-grown Caco-2 intestinal epithelial monolayers. IL-1 beta (0-100 ng/ml) produced a concentration- and time-dependent decrease in Caco-2 transepithelial resistance. Conversely, IL-1 beta caused a progressive time-dependent increase in transepithelial permeability to paracellular marker inulin. IL-1 beta-induced increase in Caco-2 TJ permeability was accompanied by a rapid activation of NF-kappa B. NF-kappa B inhibitors, pyrrolidine dithiocarbamate and curcumin, prevented the IL-1 beta-induced increase in Caco-2 TJ permeability. To further confirm the role of NF-kappa B in the IL-1 beta-induced increase in Caco-2 TJ permeability, NF-kappa B p65 expression was silenced by small interfering RNA transfection. NF-kappa B p65 depletion completely inhibited the IL-1 beta-induced increase in Caco-2 TJ permeability. IL-1 beta did not induce apoptosis in the Caco-2 cell. In conclusion, our findings show for the first time that IL-1 beta at physiologically relevant concentrations causes an increase in intestinal epithelial TJ permeability. The IL-1 beta-induced increase in Caco-2 TJ permeability was mediated in part by the activation of NF-kappa B pathways but not apoptosis.