Apoptotic pathway in the rat small intestinal mucosa is different between physiological conditions and ischemia-reperfusion

我们先前已经证明，禁食和缺血再灌注(I/R)可诱导大鼠肠黏膜细胞凋亡。人们普遍认为细胞凋亡是通过两条主要途径诱导的。将大鼠分为两组：I/R组结扎肠系膜上动脉60min，再灌流60min，禁食组禁食24或48h，再灌流60min。用DNA片段化百分率、电泳法和原位末端标记法检测肠道细胞凋亡。免疫印迹分析检测死亡配体/受体、半胱氨酸天冬氨酸氨基转移酶等凋亡蛋白的表达。测定小肠粘膜高度和线粒体脱氢酶功能。生理操作和I/R可显著诱导肠细胞凋亡。禁食组大鼠粘膜高度显著降低，线粒体功能障碍仅由I/R引起，Fas、FasL和TNFR1在两组大鼠的表达均增强。I/R后，细胞色素c和裂解caspase-9的表达显著增加。而在生理条件下，裂解caspase-8和裂解caspase-3的表达增加。生理条件通过受体介导的I型凋亡途径促进大鼠小肠粘膜的凋亡，I/R通过线粒体介导的II型途径诱导细胞凋亡。

We have previously demonstrated that fasting and ischemia-reperfusion (I/R) induced apoptosis in rat intestinal mucosa. It is widely accepted that apoptosis is induced through two main pathways. This study aimed to compare apoptotic pathways following physiological conditions including fasting and I/R. Rats were divided into two groups: the I/R group involved occlusion of the superior mesenteric artery for 60 min, followed by 60 min reperfusion; while the fasting group involved fasting for 24 or 48 h. Additional rats were infused several physiological substances into the cerebro-ventricle. Intestinal apoptosis was assessed as% fragmented DNA, by electrophoresis, and by a TUNEL assay. Apoptotic proteins including death ligands/receptors, caspases were evaluated by Western blot analysis. Small intestinal mucosal height and mitochondrial dehydrogenase function were assessed. Physiological manipulation and I/R significantly induced intestinal apoptosis. Mucosal height was significantly decreased in fasting rats, and mitochondrial dysfunction was induced only by I/R. Expressions of Fas, FasL and TNFR1 were enhanced in rats of both groups. After I/R, expressions of cytochrome c and cleaved caspase-9 were significantly increased. In contrast, expressions of cleaved caspase-8 and cleaved caspase-3 increased in the physiological conditions. Physiological conditions promoted mucosal apoptosis via receptor-mediated type I apoptotic pathway in the rat small intestine, and I/R induced apoptosis via mitochondria-mediated type II pathway.