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 24h of treatment with 50μM
patulin. Immunofluorescence microscopy showed that the TJ
proteins ZO-1 and
claudin-4, but not
occludin, had decreased after 24h and decreased from the cell-cell contact regions of TJs after 48h of
patulin treatment. Western blotting showed that the level of ZO-1 decreased after 48h of
patulin treatment, but the levels of
claudin-4 and
occludin remained at the initial level until 72h. Phosphorylation of ZO-1 was detected by 24h and increased markedly after 72h 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 48h and was completely absent after 72h. 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.