Background and Aims: Barrier function of the inflamed intestinal mucosa can be compromised by reactive oxygen metabolites that increase mucosal permeability and disrupt the actin cytoskeleton, the integrity of which is important for maintaining tight epithelial junctions. Because heat-shock protein 72 (hsp72) protects intestinal epithelial cells against injury, we determined whether resistance of Caco2/bbe (C2) intestinal monolayer barrier function was related to their high endogenous hsp72 expression. Methods: hsp72 anti-sense (C2/AS) and vector-only transfected C2 (C2/CEP4) clones, lines that exhibit low and high hsp72 expression, respectively, were studied. Permeability was assessed by measuring electrical resistance and mannitol fluxes and actin organization by confocal fluorescein isothiocyanate- phalloidin analysis. Results: Basal transepithelial electrical resistance (TER) and mannitol fluxes were not significantly different between groups. However, the oxidant monochloramine rapidly decreased TER and increased mannitol permeability of C2/AS monolayers compared with C2/ CEP4 (50% effective doses at 30 minutes were 0.53 ± 0.11 and 2.06 ± 0.34 mmol/L, respectively). Associated with these changes, decreased cell viability, dissociation and aggregation of perijunctional and stress actin filaments, loss of cell height, and increased intercellular separation were observed only in C2/AS cells treated with monochloramine. Conclusions: hsp72 protects intestinal epithelial barrier function against oxidant-induced stress, in part, by protecting the integrity of the actin cytoskeleton.
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