Figure 5
Effect of 1,25(OH) 2 D 3 on the barrier function in vitro. (A and B) Induction of TJ proteins by 1,25(OH)2D3 in Caco-2 cells. Caco-2 cells were treated with indicated dose of 1,25(OH)2D3 for 48 h, and cell lysates were analyzed by Western blot. Western blot analysis showed induction of zo-1, occludin and claudin-1 proteins after 48 h of adding to1,25(OH)2D3. (C) Expressions of zo-1, occludin, claudin-1 mRNA were assessed after adding to 1,25(OH)2D3 by real time Q-PCR. (D) TEM showed the disruption of the TJ, desmosomes, microvillus and brush border on the apical side of Caco-2 cell monolayer in the model group compared to that of the vehicle and 1,25(OH)2D3-treated group. (E) Cell monolayer was stained for occludin (red), claudin-1 (red) and zo-1(green) by immunofluorescence staining, noting the disruption of the TJ and reduction of fluorescence intensity in DSS group. (F) Effect of 1,25(OH)2D3 on TEER. A dose-dependent recovery of TEER with 1,25(OH)2D3-treated was seen. (G) Paracellular FITC-D was measured with or without 2% DSS in the absence or presence of 1,25(OH)2D3 at 10−9, 10−8, 10−7 M (administered 2 h prior to DSS) for 48 h, 1,25(OH)2D3 attenuated the epithelial hyperpermeability induced by DSS. Data were expressed as mean ± SD. a P < 0.05 vs vehicle group, b P < 0.05 vs DSS group.