Baicalin Relieves Intestinal Ischemia Reperfusion Injury By Inhibiting Endoplasmic Reticulum Stress

Objective: the accumulation of unfolded or misfolded proteins can induced endoplasmic reticulum stress (ERS) then activated ERS associated protein by ischemia reperfusion injury. As the most important protein receptor, inositol requiring enzyme 1?(IRE1?) is widely expressed in a variety of organs and tissues. ERS has important effects on epithelial cells survival in intestinal ischemia reperfusion injury (IIRI).This study investigated the role and expression of IRE1? and tumor necrosis factor receptor associated factor 2 (TRAF2) after IIRI and the mechanism of baicalin relieves IIRI.Methods: this study was divided into two sections.Section one: the role and expression of IRE1? and TRAF2 after IIRI 50 male SD rats were divided equally into tow groups: Sham operated control (n=10)and intestinal ischemia-reperfusion (I/R) injury group(n=40). Sham group animals underwent laparotomy without blocking the superior mesenteric artery (SMA). I/R groups animals underwent laparotomy with blocking 30 minutes of SMA, which was divided into 4 subgroups according to 2h, 6h, 12h, 24h of reperfusion, each subgroup included 10 ones. All animals were killed and collected intestinal tissues and plasma samples at the end of reperfusion. Morphological change of intestinal was observed by haematoxylin and eosin (HE) staining. Apoptotic index of intestinal epithelial cells were detected by means of terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling assay (TUNEL). Enzyme-linked immunosorbent assay(ELISA) techniques were used for detecting TNF-? and plasma concentration of intestinal fatty acid-binding protein (IFABP). Western blot was used to exam the expression of IRE1?, p-IRE1?,TRAF2 protein in intestinal tissues.Section two: the effects of baicalin on IRE1? and TRAF2 after IIRI24 male SD rats were divided equally into three groups: Sham operated control(n=8), intestinal ischemia-reperfusion injury(I/R) group(n=8) and baicalin pretreatment group(n=8). Modeling method was the same as section one. Pretreatment group rats were given intraperitoneally injection of baicalin (100mg/kg) about 30 minutes before model establishment. Apoptotic index of intestinal epithelial cells were detected by means of TUNEL. ELISA techniques were used for detecting TNF-a and plasma concentration of IFABP. The expression of phosphorylated inositol requiring enzyme 1?(p-IRE1?) were tested by immunohistochemistry. Western blot was used to exam the expression of GRP78, TRAF2 protein in intestinal tissues.Results: Section one: 1.The histological changes showed.-that the intestinal injury of I/R group was heavier than sham group. 2.Compare with sham group rats, the expression level of intestinal tissues TNF-?, apoptotic index and plasma IFABP were higher(F=231.462,149.032,162.491,all p<0.01).Those indexes enhanced at 2 h,peaked at 6h and 12h,then decreased at 24h. 3.The expression of TRAF2 protein and p-IRE1?/IRE1? could be up-regulated after IIRI ( F=40.473,59.59,p<0.01 ) . The expression of these protein were up-regulated 2h after reperfusion, peaked at 6h?12h reperfusion, decreased at 24h.Section two: Compare with I/R group rats, the level of intestinal tissues TNF-?,apoptotic index and plasma IFABP were lower(all p<0.01),the expression of TRAF2 protein and p-IREla were also decreased in baicalin pretreatment group. But GRP78 protein was up-regulated.Conclusion: 1. ERS was induced by IIRI, then activated IRE1? and up-regulated TRAF2. IREla/TRAF2 might be involved in regulating the inflammatory and cell apoptosis, increase its permeability after IIRI.2. Baicalin can alleviate ERS of the IIRI by GRP78 upregulation, inhibit IREla/TRAF2 signaling pathway and relieve IIRI.