INTESTINAL BARRIER FUNCTION: IN VITRO MODELS TO IDENTIFY BENEFICIAL NUTRITIONAL COMPOUNDS FOR CLINICAL AND IMF FORMULATIONS

EAF van Tol, LEM Willemsen, MA Koetsier, H Kroes, G Boehm. Numico Research B.V. Wageningen. The Netherlands. Adequate intestinal barrier integrity is key to the controlled transport of physiologically important compounds and maintaining immunosurveillance. Loss of barrier integrity is associated with a variety of diseases including chronic inflammation and allergy. The intestinal barrier is comprised of a mucus layer, forming a chemical-physical first line of defense, and the epithelium. The intestinal epithelium is a major defense system involving specific surface structures and regulation of paracellular permeability by tight junction (TJ) complexes. It is now well established that during allergic and inflammatory conditions certain cytokines disrupt TJ complexes thereby compromising the intestinal barrier integrity. We have established in vitro models to evaluate mucus production and epithelial permeabilility. An innovative intestinal epithelial/mesenchymal cell co-culture system was established mimicking the spatial and functional relation of these cells in vivo. Inflammatory and allergic cytokines were evaluated for their role in affecting epithelial permeability. In addition, isolated intestinal lamina propria mononuclear cells were introduced to assess their role in immune mediated barrier disruption. Barrier function was determined by transepithelial resistance (TER) and molecular permeability (HRP- and FD-4 flux). Effects of cytokines on TJ protein expression (western blot) and specific signaling routes were evaluated. Mucoprotective mechanisms were studied by measuring prostaglandin (ELISA) and mucin production (dot-blot). Using these models we identified nutritional compounds that improve IFN-g and IL-4 mediated barrier disruption. Moreover we found evidence for direct mucoprotective properties of these compounds and their metabolic products. It is concluded that specific nutritional formulations may support intestinal barrier function thereby improving natural resistance in both healthy individual and patients.