紧密连接Occludin蛋白在缺血性脑卒中肠屏障改变中的作用

Role of Occludin protein in intestinal barrier changes of ischemic stroke

目的 研究缺血性脑卒中时是否存在肠黏膜屏障功能改变以及紧密连接蛋白Occludin在其中的可能机制.方法 杂种犬20只,随机分为实验组和对照组（即假手术组）,每组10只.实验组采用双硅柱置入法制作缺血性脑卒中模型.实验前及实验后12、24 h行血浆内毒素脂多糖（LPS）浓度检测;光镜下对肠黏膜病理形态进行观察;免疫组化法分析肠黏膜紧密连接Occludin蛋白的表达.结果 实验组动物均形成脑梗死.与对照组比较,实验组实验后12、24 h 血浆LPS浓度显著增高,紧密连接蛋白Occludin蛋白平均光密度显著降低（P均〈0.01）.相关和回归分析显示,Occludin蛋白平均光密度与实验后12、24 h 血浆LPS浓度均呈负相关（P均〈0.05）.光镜下观察,实验组存在小肠病理损伤,对照组小肠结构正常.结论 缺血性脑卒中时肠道屏障功能有明确的损害.血浆LPS能反映缺血性脑卒中时的肠屏障损伤.缺血性脑卒中时肠黏膜紧密连接蛋白Occludin表达降低,从而导致紧密连接破坏,这是肠屏障功能障碍的重要分子机制之一.

Objective To observe intestinal barrier changes in ischemic stroke and explore the role of Occludin protein. Methods 20 mongrel dogs were randomly divided into 2 groups with 10 in each. Double silicone cylinders measuring （ 1.1 mm × 8 mm） were placed into their internal carotid arteries in all dogs of group A, and group B was served as control group with sham operation. Blood samples were taken at 3 time points： before operation （0 h）, at 12 and 24 h after operation. The concentration of plasma lipopolysaccharide was measured at 3 time points. Light microscopic examination was performed for morphological measurement of intestinal epithelial cell. lmmunohistochemistry was used to analyze the changes of Occludin protein localizing at tight junction of intestinal epithelial cells. Results Ischemic stroke was confirmed by cranial CT scanning in all dogs of group A. Compared with the test results in group B,the results of lipopolysaccharide at 12, 24 h increased significantly in all dogs of group A. The Occludin protein level in group A was significantly lower than that in group B （ P 〈 0. 01 ）. There were negative correlations between the level of Oecludin protein and LPS at 12 and 24 h. Under the light microscope, intestinal mucosal injuries were seen in group A, and no obvious changes occurred in group B. Conclusion There is intestinal barrier dysfunction in ischemic stroke. The concentration of lipopolysaccharide in plasma changed with the destruction of intestinal mucosal function. Destruction of tight junction is one of the molecular mechanisms of pathogenesis of intestinal barrier dysfunction in ischemie stroke.