Activation of the Epithelial-to-Mesenchymal Transition Factor Snail Mediates Acetaldehyde-Induced Intestinal Epithelial Barrier Disruption.

BACKGROUND: Acetaldehyde (AcH) is mutagenic and can reach high colonic lumen after ethanol consumption and is associated with dysfunction and an increased risk of progressive cancers, including carcinoma. Snail, the transcription factor of epithelial-mesenchymal is known to down-regulate expression of tight junction (TJ) and adherens (AJ) proteins, resulting in loss of epithelial integrity, cancer metastases. As AcH is mutagenic, the role of Snail in the AcH-induced of intestinal epithelial TJs deserves further investigation. Our aim was investigate the role of oxidative stress and Snail activation in AcH- barrier disruption in Caco-2 monolayers. METHODS: The monolayers were from the apical side to AcH +/- L-cysteine. Reactive oxygen species generation and Snail activation were assessed by ELISA and Paracellular permeability, localization, and expression of ZO-1, E-cadherin, and beta-catenin were examined using transepithelial resistance (TEER), fluorescein isothiocyanate-labeled dextran 4 kDa immunofluorescence, and ELISA, respectively. Involvement of Snail was addressed by inhibiting Snail using small interfering RNA (siRNA). Exposure to 25 muM AcH increased ROS generation and ROS-dependently phosphorylation. In addition, AcH increased paracellular permeability in TEER and increase in FITC-D4 permeation) in association with and decrease of TJ and AJ protein levels, which could be attenuated by L-cysteine. Knockdown of Snail by siRNA attenuated the AcH-induced and decrease in the TJ and AJ proteins, in association with improvement barrier function. CONCLUSIONS: Our data demonstrate that oxidative stress-mediated Snail phosphorylation is likely a novel mechanism the deleterious effects of AcH on the TJ and AJ, and intestinal barrier