Abstract
Diminished intestinal epithelial barrier function contributes to the pathogenesis of Crohn's disease. Clinical and experimental studies propose that increased tumor necrosis factor (TNF)-alpha promotes barrier dysfunction. The aim of this study was to investigate the effects of nutritional and other therapies upon intestinal barrier function in the presence of TNF-alpha in an in vitro model.
Caco-2 monolayers were grown to confluence on membrane supports and then exposed to TNF-alpha in the presence of polymeric formula, hydrocortisone or infliximab. Monolayer permeability was evaluated by measuring epithelial resistance, short-circuit current and horseradish peroxidase flux in an Ussing chamber. Tight junction and myosin II regulatory light-chain kinase gene expression was analysed by real-time PCR, with protein expression and localization analysed by Western blot and immunofluorescence.
TNF-alpha increased monolayer permeability and diminished tight junction integrity. However both polymeric formula and infliximab completely abrogated the effects of TNF-alpha. These monolayers displayed unchanged permeability and tight junction integrity compared to untreated cells (media-no-TNF-alpha controls). In contrast, hydrocortisone only partially abrogated the effects of TNF-alpha, with these monolayers having increased permeability and altered tight junction integrity compared to media-no-TNF-alpha controls.
Both polymeric formula and infliximab completely prevent epithelial barrier dysfunction in the presence of TNF-alpha, whereas hydrocortisone partially prevents barrier dysfunction. These results provide evidence that superior mucosal healing can be achieved with both polymeric formula and infliximab compared to hydrocortisone.