Correlation between the destruction of tight junction by patulin treatment and increase of phosphorylation of ZO-1 in Caco-2 human colon cancer cells

Patulin is a mycotoxin and its contamination of food has been reported to cause gastrointestinal inflammation, ulcers, and bleeding. The toxicity of patulin is thought to be due to the destruction of tight junctions (TJs) in gastrointestinal tissues. However, the precise mechanism has not been clarified. Here, we investigated the phosphorylation of TJ components. The transepithelial electrical resistance (TER) of Caco-2 human colon cancer cells decreased gradually during the first 24 h of treatment with 50 mu M patulin. Immunofluorescence microscopy showed that the TJ proteins ZO-1 and claudin-4, but not occludin, had decreased after 24 h and decreased from the cell-cell contact regions of TJs after 48 h of patulin treatment. Western blotting showed that the level of ZO-1 decreased after 48 h of patulin treatment, but the levels of claudin-4 and occludin remained at the initial level until 72 h. Phosphorylation of ZO-1 was detected by 24 h and increased markedly after 72 h of patulin treatment. However, phosphorylation of claudin-4 and occludin was not detected by probing with anti-phosphotyrosine antibody. Immunoprecipitation showed that interaction of ZO-1 with claudin-4 had decreased after 48 h and was completely absent after 72 h. These results suggest that phosphorylation caused the degradation of ZO-1 protein and the decrease in TER induced by patulin treatment of Caco-2 cells. (C) 2011 Elsevier Ireland Ltd. All rights reserved.