The Protective Effect Of Emodin On Intestinal Mucosal Barrier Injury Induced By Hvpoxia/Reoxysenation And The Investigation Of Its Mechanism

Objective:The intestinal mucosal barrier (IMB) is primarily composed of mechanical, biological and immunologic barriers, and the mechanical barrier is the most important component, which including the intestinal epithelial cells and the intercellular tight junction. The intact IMB can prevent the invasion of pathogenic microorganism, thus maintain the homeostasis of the human body. Emodin, an active natural anthraquinone derivatived from traditional Chinese herbal medicines, has been shown with comprehensive pharmacological activities, Some studies had confirmed certain protective effects of emodin on IMB recently. Comparing with other internal organs, the intestine is the most sensitive one to IR injury in the body. Apoptosis is a major mode of cell death caused by ischaemia/reperfusion injury to the intestinal epithelium. The endoplasmic reticulum stress (ERS) is a new way of cell apoptosis which was discovered recently, it takes part in the cause of many diseases and injuries. In this study, Hypoxia/reoxygenation (H/R) model of intestinal epithelial cells were established. The purpose was to investigate the mechanism of the effects of emodin and ERS on the intestinal mucosal barrier injury induced by H/R.Methods:Bowel epithelial cell lines Caco-2cells were cultured in vitro to establish H/R model. The cells were averagely randomized into four groups:N (normal cells) group, H/R+EN (hypoxia/reoxygenation and Emodin) group, H/R (hypoxia/reoxygen-ation) group, H/R+HBSS (hypoxia/reoxygenation and Hanks balanced solution) group. The transepithelial electrical resistance (TEER) value, the ultrastructure of TJ, the expression level of TJ protein and specific protein of ERS and the apoptosis index (AI) were determined and observed.Results:In the H/R injury model of H/R+EN group, H/R group, H/R+HBSS group, the damage of TJ was severe; the TEER value, the protein expression level of Occludin and ZO-1were decreased obviously; the protein and mRNA expression level of GRP78and Caspase-4, the AI were increased significantly. Comparing with H/R group and H/R+HBSS group, the damage of TJ was reduced significantly in the H/R+EN group; the TEER value, the protein expression level of Occludin and ZO-1were increased obviously; the protein and mRNA expression level of GRP78and Caspase-4, the AI were all decreased significantly.Conclusion:ERS serves as an autoprotective mechanism for the H/R injury to intestinal epithelial cells. However, due to the persistent severe injury, ERS may turn to promote apoptosis, thus causing the injury of the integrity of intestinal mucosa barrier. Emodin can protect the tight junction of intestinal epithelial cells, and inhibit the excessive ERS through reducing the expression of GRP78and Caspase-4to protect the intestinal mucosa barrier.