COX-2/EP2-EP4/β-catenin signaling regulates patulin-induced intestinal cell proliferation and inflammation

Patulin (PAT), a mycotoxin, is a natural contaminant that is produced by certain species of Penicillium, Aspergillus and Byssochlamys. The major contamination of PAT is in apple and apple based products. PAT is known to cause glutathione depletion, oxidative DNA damage and cell proliferation. Recently, in vitro studies have indicated that PAT can also increase the intestinal epithelial permeability, modulate tight junctions and decrease transepithelial electrical resistance. Nonetheless, no previous study has evaluated the mechanisms responsible for PAT-induced intestinal toxicity or its relevance to the in vivo situation. Here, Wistar rats were orally treated with 100 μg/kg body weight (b.wt.) of PAT, either alone or along with 100 mg/kg b. wt. of celecoxib for 3 days. We found that PAT exposure led to significantly higher levels of PGE₂ in serum and intestinal tissue and high expression of COX-2 and Ki-67 compared to controls. Interestingly, our results showed that celecoxib treatment could decrease the PAT-induced PGE₂ and reduce the PAT-induced intestinal damage. To study the mechanistic aspect, normal rat intestinal epithelial cells (IEC-6) were treated with non-toxic concentrations (100 nM, 250 nM and 500 nM) of PAT for 6 h. It was observed that PAT exposure caused enhanced proliferation, higher expression of COX-2, and EP2 and EP4 receptors, along with increased PGE₂ secretion. Additionally, PAT exposure caused enhanced Akt expression, which in turn inhibits GSK-3β and stabilizes β-catenin. Overall, our study suggests that the COX-2/EP2-EP4/β-catenin signaling cascades are involved in the regulation of PAT-induced intestinal cell proliferation and inflammation.