Modulation of epithelial tight junctions by TGF-beta 3 in cultured oral epithelial cells.

Background: Previous studies have indicated that transforming growth factor beta 3 (TGF-β3) was strongly expressed both in the gingival epithelium and the poorly structured pocket epithelium.

Methods: A comprehensive analysis of the profile of tight junction proteins was carried out by quantitative real-time RT-PCR, Western blot and paracellular permeability assays.

Results: Active TGF-β3 protein added to monolayers of cultured oral epithelial cells initially reduced the permeability to dextran (10 kDa), followed by an increase in permeability. Three hours after the addition of TGF-β3, expression of genes encoding tight junction components was selectively up- or down-regulated. In addition, up- or down-regulation of expression of several tight junction associated proteins was observed, although the protein changes did not parallel changes in gene expression. To confirm that TGF-β3 plays a role in epithelial barrier function, a selective Src family kinase inhibitor saracatinib (AZD0530) was added to cells treated with active TGF-β3. Tight junction proteins claudins-2, -20 and ZO-2 were significantly decreased, but claudin-4 and -18 were significantly increased.

Conclusions: These results suggest that TGF-β3 is involved in the modulation of epithelial barrier function by regulating assembly of tight junctions.