Notch signaling plays a critical role in the maintenance of intestinal homeostasis. The aim of the present study was to investigate the role of Notch signaling in the apoptosis of intestinal epithelial cells after intestinal ischemia reperfusion (I/R) injury. Male C57BL/6 mice were subjected to sham operation or I/R injury. Intestinal tissue samples were collected at 12 h after reperfusion. TUNEL (terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling) staining showed that intestinal I/R injury induced significantly increased apoptosis of intestinal epithelial cells. Meanwhile, the mRNA expression of Jagged1, DLL1, Notch2, and Hes5, and protein expression of NICD2 and Hes5 were increased significantly after I/R injury in intestinal epithelial cells. In an in vitro IEC-6 culture model, flow cytometry analyses showed that inhibition of Notch signaling by γ-secretase inhibitor DAPT and the suppression of Hes5 expression using siRNA both significantly increased the apoptosis of IEC-6 cells under the condition of hypoxia/ reoxygenation (H/R). In conclusion, the Notch2/Hes5 signaling pathway was activated and involved in the regulation of intestinal epithelial cells apoptosis in intestinal I/R injury.

Interleukin-33(IL33), an alarm cytokine of the IL-1 family, is expressed mainly in epithelial cells of barrier tissues and is involved in the repair of epithelia to maintain barrier function. However, the mechanisms regulating IL33 expression and the mechanisms by which IL33 regulates the intestinal barrier function are not fully clarified. In this study, Caco-2 cells and siRNA were applied to investigate the role of Notch/IL33/ST2 Signaling in regulating intestinal epithelial barrier function, which was demonstrated by protein expression of tight junctions and trans-epithelial resistance (TER) assay. Our results revealed that Notch signaling pathway was activated and IL33 expression was up-regulated after LPS stimulation. After blocking Notch signaling with DPAT or siRNA for Notch1, IL33 expression was significantly down-regulated in Caco-2 cells. The protein expression of tight junctions (ZO-1, occludin, and claudin-1) was down-regulated after siRNA for IL33 in Caco-2 cells with LPS stimulation. Also, the intestinal epithelial TER was down-regulated after siRNA for IL33 with LPS stimulation or not. Exogeneous IL33 promoted the tight junction protein expression and increased the TER. Finally, our data further showed that IL33 regulates intestinal epithelial barrier function through the ST2 receptor. In conclusion, our results indicated that IL33/ST2 axis, which was activated by the Notch signaling, maintains intestinal epithelial barrier function through regulating tight junction protein expression under inflammatory conditions. This study provides a new therapeutic pathway of regulating intestinal epithelial barrier dysfunction.