| Objective: Obstructive jaundice results in intestinal mucosal barrier dysfunction with consequent a series of complications, such as septicaemia and renal failure. The key event in the pathophysiology of obstructive jaundice-associated complications is endotoxemia of gut origin because of intestinal barrier failure. Experimental and clinical studies have shown that gut barrier dysfunction in obstructive jaundice is associated with increased intestinal permeability. Increased intestinal permeability has been postulated to be a key factor contributing to bacterial and endotoxin translocation and the pathogenesis of septicaemia and renal failure in patients with obstructive jaundice. However, little is known of the molecular events leading to increased intestinal permeability with obstructive jaundice. It has been demonstrated by experimental studies that increased intestinal permeability with obstructive jaundice is associated with the changes of intestinal epithelial tight junction protein. Tight junctions are located at the apical parts of lateral membranes of epithelial and endothelial cells, forming a barrier that regulates the permeability of ions, macromolecules and cells through the paracellular pathway. They include occludin,claudins,ZOs and junctional adhesion molecule. The aim of this study is to observe the changes in intestinal morphology and ultrastructure of patients with obstructive jaundice, to detect the concentration of serum endotoxin and diamine oxidase by spectrophotometry and to evaluate immunohistochemically the expression of tight junction protein claudin-1 and claudin-4 in intestinal mucosa of patients with obstructive jaundice in order to further investigate the mechanism of intestinal barrier failure with obstructive jaundice.Methods: Twenty-five patients with biliary obstruction who accepted ERCP examination or treatment in the Department of Gastroenterology of The Second Hospital of Hebei Medical University from May 2008 to Dec 2008 were collected. Among them, fifteen patients suffering from obstruction with jaundice were regarded as obstructive jaundice group, six patients with choledocholithiasis and nine patients with periampullary carcinoma; ten patients suffering from obstruction without jaundice were regarded as obstruction without jaundice group, six patients with choledocholithiasis and four patients with periampullary carcinoma. Choosing ten healthy subjects of routine gastroscopy was regarded as normal control group. In the morning of endoscopic procedure, fasting blood of all patients were collected from peripheral vein to detect the concentration of serum endotoxin and diamine oxidase by spectrophotometry. The tissue specimens of all patients were obtained from the second part of the duodenum, distal to the ampulla of Vater by endoscopic biopsy. For electron microscopic analyses, one tissue specimen was fixed in 4% glutaraldehyde, and electron microscopy was performed to observe the ultrastructural changes of intestinal mucosa. Two tissue specimens were fixed in 10% formalin, embedded in paraffin, sectioned at 4μm and stained with hematoxylin and eosin (HE) for routine light microscopic examination. The morphological changes of the intestinal mucosa and pathological scores for intestinal mucosal injury were observed by light microscopy. In addition, tissue sections of all patients were examined immunohistochemically for evaluation of the expressions of tight junction protein claudin-1 and claudin-4 in the intestinal epithelium. All the data were analyzed by statistical software SPSS 10.0 version.Results:1. The tissue sections were examined histologically by light microscopy. In the patients of control group and obstruction without jaundice group, the intestinal villus remained intact and enterocytes arrayed neatly. But the intestinal mucosa of the patients with obstructive jaundice was damaged, illustrating extension of the subepithelial space with moderate lifting of the epithelial layer from the lamina propria and epithelial lifting down the sides of the villus and denuded villus. The scores for intestinal mucosal injury of the patients of obstructive jaundice group (2.60±0.51) were significantly higher than that of control group (0.40±0.52) (P<0.05) and obstruction without jaundice group (0.50±0.53) (P<0.05). But there was no statistically difference between control group and obstruction without jaundice group (P>0.05).2. The ultrastructure of intestinal mucosa was observed by transmission electron microscopy. In the patients of control group and obstruction without jaundice group, the microvillus and apical junctional complexes including tight junctions remained intact. When we evaluated the patients with obstructive jaundice, we observed that the microvillus were loose and the structures of junctional complexes were disrupted and the gap of cell junctions were wider.3. For the results of ET and DAO, the levels of serum ET and DAO of obstructive jaundice group (0.15±0.02, 4.25±0.64) were higher than that of control group (0.03±0.01, 1.58±0.57) (P<0.05) and obstruction without jaundice group (0.03±0.01, 1.71±0.88) (P<0.05). But there was no statistically difference between control group and obstruction without jaundice group in the levels of serum ET and DAO (P>0.05). Moreover, in the patients with obstructive jaundice, the levels of serum ET were positive correlation to that of TB (r=0.856, P<0.05) and DAO (r=0.697, P<0.05); there was positive correlation between the levels of serum DAO and TB (r=0.752, P<0.05). In addition, there was no statistically difference between the patients with choledocholithiasis and with periampullary carcinoma in the levels of serum ET and DAO of obstructive jaundice group (P>0.05).4. For the results of immunohistochemistry, claudin-1 and claudin-4 immunohistochemical staining in intestinal mucosa appeared positive with brown at plasma membrane of enterocytes and blue at nucleus. It was demonstrated by measurement of the average optical density value that intestinal mucosal claudin-1 protein levels of obstructive jaundice group (16.22%±1.16%) were lower than that of control group (23.44%±1.27%) (P<0.05) and obstruction without jaundice group (23.06%±0.90%) (P<0.05), but claudin-4 protein levels of obstructive jaundice group (29.41%±1.36%) were higher than that of control group (24.02%±1.21%) (P<0.05) and obstruction without jaundice group (24.39%±1.09%) (P<0.05). There was no statistically difference between control group and obstruction without jaundice group in claudin-1 and claudin-4 protein levels (P>0.05). In addition, there was no statistically difference between the patients with choledocholithiasis and with periampullary carcinoma in claudin-1 and claudin-4 protein levels of obstructive jaundice group (P>0.05).Conclusion: The patients with obstructive jaundice induced intestinal mucosal injury with consequent gut derived endotoxemia. The claudin-1 expression was decreased and claudin-4 expression was increased in intestinal epithelium of patients with obstructive jaundice, which could relate to the mechanism of intestinal barrier failure with obstructive jaundice.
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