Fatty acids and epithelial permeability: effect of conjugated linoleic acid in Caco-2 cells

Conjugated linoleic acid (CLA) is a collective term referring to the positi onal and geometric isomers of linoleic acid. This novel fatty acid has been shown to have a number of beneficial actions, including immunomodulatory, anticarcinogenic, and antiatherogenic effects. Tight junctions of epithelia l cells determine epithelial membrane integrity and selective paracellular permeability to ions and macromolecules. Occludin and ZO-1 are integral str uctural components of the tight junction, which are involved in the biogene sis and functional integrity of the epithelial monolayer. This study invest igated the effects of two isomers of CLA (cis-9 and trans-10 isomers) on Ca co-2 cell transepithelial resistance (TER) development, paracellular epithe lial permeability, and occludin and ZO-1 expression. Caco-2 cells were grow n in media supplemented with 0.05 mM linoleic acid, cis-9 CLA, or trans-10 CLA for 21 days. The trans-10 CLA isomer delayed Caco-2 cell TER developmen t, which is an in vitro measure of epithelial cell integrity, and increased paracellular epithelial permeability. Immunofluorescent staining of Caco-2 cell epithelial monolayers grown in media supplemented trans-10 CLA showed that the trans-10 CLA isomer altered distribution of occludin and ZO-1. Th e trans-10 CLA isomer delayed the acquisition of transepithelial resistance and altered the cellular distribution of occludin, which have important im plications in relation to epithelial permeability.