EFFECT OF INTESTINAL EPITHELIAL CELL AUTOPHAGY ON THE EXPRESSION OF TIGHT JUNCTION PROTEINS IN DAMAGED CACO-2 CELLS INDUCED BY LIPOPOLYSACCHARIDE
Objective To investigate the effect of intestinal epithelial cell autophagy on the expression of tight junction (TJ) proteins in colon cancer cell line (Caco-2) in the model of lipopolysaccharide (LPS)-induced injury in intestinal epithelial cells.Methods In human Caco-2 cells,a model of intestinal epithelial injury induced by LPS was established.These cells were divided into control group (group A),LPS group (group B),and LPS combined with autophagy inhibitor 3-methyladenine (3 MA) group (group C).The transepithelial electrical resistance (TER) of Caco 2 cells was measured by a resistance apparatus,and the intercellular permeability was evaluated by the paracellular transport of fluorescein isothiocyanate-dextran (FITC-dextran).The protein expression of the autophagic marker microtubule-associated protein 1 light chain 3 Ⅱ (LC3Ⅱ) and the TJ proteins Zonula occluden1 (ZO-1),claudins 2 (CL-2),and occludin (OC) was measured by Western blot,and the mRNA expression of CL-2,ZO-1,and OC was measured by reverse transcription RT-PCR.Results Compared with group A and group B,group C showed significantly lower TER values at different points (F=83.82-271.83,P＜0.05),higher intercellular permeability for FIT-D4 (F=724.92,P＜0.05),and reduced protein expression of LC3 Ⅱ (F=134.72,P＜0.05).Group C also had increased protein expression of CL2 as well as reduced protein expression of ZO-1 and OC compared with group B (F=90.03-329.08,P＜0.05).RT-PCR analysis showed that group C had significantly increased mRNA expression of CL-2 and significantly reduced mRNA expression of ZO-1 and OC compared with group B (F=339.81-580.32,P＜0.05).Conclusion Intestinal epithelial cell autophagy may down regulate the expression of CL2 and up-regulate the expression of ZO-1 and OC in damaged intestinal epithelial cells induced by LPS,to maintain the intestinal epithelial TJ,thus protecting the intestinal epithelial barrier.
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